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Álvarez-Quintero N, Kim SY. Effects of maternal age and environmental enrichment on learning ability and brain size. Behav Ecol 2024; 35:arae049. [PMID: 38952837 PMCID: PMC11215699 DOI: 10.1093/beheco/arae049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Revised: 05/27/2024] [Accepted: 06/10/2024] [Indexed: 07/03/2024] Open
Abstract
It is well known that maternal age at reproduction affects offspring lifespan and some other fitness-related traits, but it remains understudied whether maternal senescence affects how offspring respond to their environments. Early environment often plays a significant role in the development of an animal's behavioral phenotype. For example, complex environments can promote changes in cognitive ability and brain morphology in young animals. Here, we study whether and how maternal effect senescence influences offspring plasticity in cognition, group behavior, and brain morphology in response to environmental complexity. For this, juvenile 3-spined sticklebacks from young and old mothers (i.e. 1-yr and 2-yr-old) were exposed to different levels of environmental enrichment and complexity (i.e. none, simple, and complex), and their behavior, cognitive ability, and brain size were measured. Exposing fish to enriched conditions improved individual learning ability assessed by a repeated detour-reaching task, increased the size of the whole brain, and decreased aggressive interactions in the shoal. Maternal age did not influence the inhibitory control, learning ability, and group behavioral responses of offspring to the experimental environmental change. However, maternal age affected how some brain regions of offspring changed in response to environmental complexity. In offspring from old mothers, those exposed to the complex environment had larger telencephalons and cerebellums than those who experienced simpler environments. Our results suggest that maternal effect senescence may influence how offspring invest in brain functions related to cognition in response to environmental complexity.
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Affiliation(s)
- Náyade Álvarez-Quintero
- Grupo de Ecoloxía Animal, Centro de Investigación Mariña, Universidade de Vigo, Fonte das Abelleiras, s/n, Vigo, 36310 Pontevedra, Spain
- Dipartimento di Biologia, Complesso Interdepartamentale A. Vallisneri, Università di Padova, Via Ugo Bassi, 58b, 35121 Padova PD, Italy
| | - Sin-Yeon Kim
- Grupo de Ecoloxía Animal, Centro de Investigación Mariña, Universidade de Vigo, Fonte das Abelleiras, s/n, Vigo, 36310 Pontevedra, Spain
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2
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Suryadevara V, Hudgins AD, Rajesh A, Pappalardo A, Karpova A, Dey AK, Hertzel A, Agudelo A, Rocha A, Soygur B, Schilling B, Carver CM, Aguayo-Mazzucato C, Baker DJ, Bernlohr DA, Jurk D, Mangarova DB, Quardokus EM, Enninga EAL, Schmidt EL, Chen F, Duncan FE, Cambuli F, Kaur G, Kuchel GA, Lee G, Daldrup-Link HE, Martini H, Phatnani H, Al-Naggar IM, Rahman I, Nie J, Passos JF, Silverstein JC, Campisi J, Wang J, Iwasaki K, Barbosa K, Metis K, Nernekli K, Niedernhofer LJ, Ding L, Wang L, Adams LC, Ruiyang L, Doolittle ML, Teneche MG, Schafer MJ, Xu M, Hajipour M, Boroumand M, Basisty N, Sloan N, Slavov N, Kuksenko O, Robson P, Gomez PT, Vasilikos P, Adams PD, Carapeto P, Zhu Q, Ramasamy R, Perez-Lorenzo R, Fan R, Dong R, Montgomery RR, Shaikh S, Vickovic S, Yin S, Kang S, Suvakov S, Khosla S, Garovic VD, Menon V, Xu Y, Song Y, Suh Y, Dou Z, Neretti N. SenNet recommendations for detecting senescent cells in different tissues. Nat Rev Mol Cell Biol 2024:10.1038/s41580-024-00738-8. [PMID: 38831121 DOI: 10.1038/s41580-024-00738-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/15/2024] [Indexed: 06/05/2024]
Abstract
Once considered a tissue culture-specific phenomenon, cellular senescence has now been linked to various biological processes with both beneficial and detrimental roles in humans, rodents and other species. Much of our understanding of senescent cell biology still originates from tissue culture studies, where each cell in the culture is driven to an irreversible cell cycle arrest. By contrast, in tissues, these cells are relatively rare and difficult to characterize, and it is now established that fully differentiated, postmitotic cells can also acquire a senescence phenotype. The SenNet Biomarkers Working Group was formed to provide recommendations for the use of cellular senescence markers to identify and characterize senescent cells in tissues. Here, we provide recommendations for detecting senescent cells in different tissues based on a comprehensive analysis of existing literature reporting senescence markers in 14 tissues in mice and humans. We discuss some of the recent advances in detecting and characterizing cellular senescence, including molecular senescence signatures and morphological features, and the use of circulating markers. We aim for this work to be a valuable resource for both seasoned investigators in senescence-related studies and newcomers to the field.
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Affiliation(s)
- Vidyani Suryadevara
- Department of Radiology, Molecular Imaging Program at Stanford (MIPS), Stanford University, School of Medicine, Stanford, CA, USA
| | - Adam D Hudgins
- Department of Obstetrics and Gynecology, Columbia University, New York, NY, USA
| | - Adarsh Rajesh
- Sanford Burnham Prebys Medical Discovery Institute, Cancer Genome and Epigenetics Program, La Jolla, CA, USA
| | | | - Alla Karpova
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Amit K Dey
- National Institute on Aging, NIH, Baltimore, MD, USA
| | - Ann Hertzel
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA
- Institute on the Biology of Aging and Metabolism, University of Minnesota, Minneapolis, MN, USA
| | - Anthony Agudelo
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA
- Center on the Biology of Aging, Brown University, Providence, RI, USA
| | - Azucena Rocha
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA
- Center on the Biology of Aging, Brown University, Providence, RI, USA
| | - Bikem Soygur
- The Buck Institute for Research on Aging, Novato, CA, USA
| | | | - Chase M Carver
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
- Robert and Arlene Kogod Center on Aging, Rochester, MN, USA
| | - Cristina Aguayo-Mazzucato
- Islet Cell Biology and Regenerative Medicine, Joslin Diabetes Center, Harvard Medical School, Boston, USA
| | - Darren J Baker
- Robert and Arlene Kogod Center on Aging, Rochester, MN, USA
- Department of Biochemistry and Molecular Biology, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN, USA
| | - David A Bernlohr
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA
- Institute on the Biology of Aging and Metabolism, University of Minnesota, Minneapolis, MN, USA
| | - Diana Jurk
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
- Robert and Arlene Kogod Center on Aging, Rochester, MN, USA
- Department of Neurology, Mayo Clinic, Rochester, MN, USA
| | - Dilyana B Mangarova
- Department of Radiology, Molecular Imaging Program at Stanford (MIPS), Stanford University, School of Medicine, Stanford, CA, USA
| | - Ellen M Quardokus
- Department of Intelligent Systems Engineering, Indiana University, Bloomington, IN, USA
| | | | - Elizabeth L Schmidt
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA
- Institute on the Biology of Aging and Metabolism, University of Minnesota, Minneapolis, MN, USA
| | - Feng Chen
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Francesca E Duncan
- The Buck Institute for Research on Aging, Novato, CA, USA
- Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, IL, USA
| | | | - Gagandeep Kaur
- Department of Environmental Medicine, University of Rochester Medical Center, Rochester, NY, USA
| | - George A Kuchel
- UConn Center on Aging, University of Connecticut Health Center, Farmington, CT, USA
- Department of Genetics and Genome Sciences, University of Connecticut Health Center, Farmington, CT, USA
| | - Gung Lee
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
- Robert and Arlene Kogod Center on Aging, Rochester, MN, USA
| | - Heike E Daldrup-Link
- Department of Radiology, Molecular Imaging Program at Stanford (MIPS), Stanford University, School of Medicine, Stanford, CA, USA
| | - Helene Martini
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
- Robert and Arlene Kogod Center on Aging, Rochester, MN, USA
| | - Hemali Phatnani
- New York Genome Center, New York, NY, USA
- Department of Neurology, Columbia University Irving Medical Center, New York, NY, USA
| | - Iman M Al-Naggar
- UConn Center on Aging, University of Connecticut Health Center, Farmington, CT, USA
| | - Irfan Rahman
- Department of Environmental Medicine, University of Rochester Medical Center, Rochester, NY, USA
| | - Jia Nie
- Barshop Institute for Longevity and Aging Studies, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA
| | - João F Passos
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
- Robert and Arlene Kogod Center on Aging, Rochester, MN, USA
| | - Jonathan C Silverstein
- Department of Biomedical Informatics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Judith Campisi
- The Buck Institute for Research on Aging, Novato, CA, USA
| | - Julia Wang
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Kanako Iwasaki
- Islet Cell Biology and Regenerative Medicine, Joslin Diabetes Center, Harvard Medical School, Boston, USA
| | - Karina Barbosa
- Sanford Burnham Prebys Medical Discovery Institute, Cancer Genome and Epigenetics Program, La Jolla, CA, USA
| | - Kay Metis
- Department of Biomedical Informatics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Kerem Nernekli
- Department of Radiology, Molecular Imaging Program at Stanford (MIPS), Stanford University, School of Medicine, Stanford, CA, USA
| | - Laura J Niedernhofer
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN, USA
- Institute on the Biology of Aging and Metabolism, University of Minnesota, Minneapolis, MN, USA
| | - Li Ding
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Lichao Wang
- UConn Center on Aging, University of Connecticut Health Center, Farmington, CT, USA
- Department of Genetics and Genome Sciences, University of Connecticut Health Center, Farmington, CT, USA
| | - Lisa C Adams
- Department of Radiology, Molecular Imaging Program at Stanford (MIPS), Stanford University, School of Medicine, Stanford, CA, USA
| | - Liu Ruiyang
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Madison L Doolittle
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
- Robert and Arlene Kogod Center on Aging, Rochester, MN, USA
- Division of Endocrinology, Diabetes and Metabolism, Mayo Clinic, Rochester, MN, USA
| | - Marcos G Teneche
- Sanford Burnham Prebys Medical Discovery Institute, Cancer Genome and Epigenetics Program, La Jolla, CA, USA
| | - Marissa J Schafer
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
- Robert and Arlene Kogod Center on Aging, Rochester, MN, USA
- Department of Neurology, Mayo Clinic, Rochester, MN, USA
| | - Ming Xu
- UConn Center on Aging, University of Connecticut Health Center, Farmington, CT, USA
- Department of Genetics and Genome Sciences, University of Connecticut Health Center, Farmington, CT, USA
| | - Mohammadjavad Hajipour
- Department of Radiology, Molecular Imaging Program at Stanford (MIPS), Stanford University, School of Medicine, Stanford, CA, USA
| | | | | | - Nicholas Sloan
- Department of Neurology, Columbia University Medical Center, New York, NY, USA
| | - Nikolai Slavov
- Center on the Biology of Aging, Brown University, Providence, RI, USA
- Department of Bioengineering, Northeastern University, Boston, MA, USA
- Department of Biology, Northeastern University, Boston, MA, USA
- Barnett Institute for Chemical and Biological Analysis, Northeastern University, Boston, MA, USA
| | - Olena Kuksenko
- Department of Neurology, Columbia University Medical Center, New York, NY, USA
| | - Paul Robson
- The Jackson Laboratory for Genomic Medicine, Farmington, CT, USA
- Institute for Systems Genomics, University of Connecticut, Farmington, CT, USA
| | - Paul T Gomez
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
- Robert and Arlene Kogod Center on Aging, Rochester, MN, USA
| | - Periklis Vasilikos
- Department of Genetics and Development, Columbia University, New York, NY, USA
| | - Peter D Adams
- Sanford Burnham Prebys Medical Discovery Institute, Cancer Genome and Epigenetics Program, La Jolla, CA, USA
| | - Priscila Carapeto
- Islet Cell Biology and Regenerative Medicine, Joslin Diabetes Center, Harvard Medical School, Boston, USA
| | - Quan Zhu
- Center for Epigenomics, University of California, San Diego, CA, USA
| | | | | | - Rong Fan
- Yale-Center for Research on Aging, Yale School of Medicine, New Haven, CT, USA
| | - Runze Dong
- Department of Biochemistry, University of Washington, Seattle, WA, USA
- Graduate Program in Biological Physics, Structure and Design, University of Washington, Seattle, WA, USA
| | - Ruth R Montgomery
- Yale-Center for Research on Aging, Yale School of Medicine, New Haven, CT, USA
| | - Sadiya Shaikh
- Department of Environmental Medicine, University of Rochester Medical Center, Rochester, NY, USA
| | - Sanja Vickovic
- New York Genome Center, New York, NY, USA
- Herbert Irving Institute for Cancer Dynamics, Columbia University, New York, NY, USA
- Department of Biomedical Engineering, Columbia University, New York, NY, USA
- Science for Life Laboratory, Department of Immunology, Genetics and Pathology, Beijer Laboratory for Gene and Neuro Research, Uppsala University, Uppsala, Sweden
| | - Shanshan Yin
- Sanford Burnham Prebys Medical Discovery Institute, Cancer Genome and Epigenetics Program, La Jolla, CA, USA
| | - Shoukai Kang
- Department of Biochemistry, University of Washington, Seattle, WA, USA
| | - Sonja Suvakov
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN, USA
| | - Sundeep Khosla
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
- Robert and Arlene Kogod Center on Aging, Rochester, MN, USA
- Division of Endocrinology, Diabetes and Metabolism, Mayo Clinic, Rochester, MN, USA
| | - Vesna D Garovic
- Department of Obstetrics and Gynecology, Mayo Clinic, Rochester, MN, USA
- Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN, USA
| | - Vilas Menon
- Department of Neurology, Columbia University Irving Medical Center, New York, NY, USA
- Center for Translational and Computational Neuroimmunology, Columbia University Irving Medical Center, New York, NY, USA
| | - Yanxin Xu
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, MA, USA
- Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA
- Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Yizhe Song
- Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Yousin Suh
- Department of Obstetrics and Gynecology, Columbia University, New York, NY, USA
- Department of Genetics and Development, Columbia University, New York, NY, USA
| | - Zhixun Dou
- Center for Regenerative Medicine, Massachusetts General Hospital, Boston, MA, USA
- Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA
- Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Nicola Neretti
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, USA.
- Center on the Biology of Aging, Brown University, Providence, RI, USA.
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3
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Aubier TG, Galipaud M. Senescence evolution under the catastrophic accumulation of deleterious mutations. Evol Lett 2024; 8:212-221. [PMID: 38525026 PMCID: PMC10959475 DOI: 10.1093/evlett/qrad050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 08/25/2023] [Accepted: 09/19/2023] [Indexed: 03/26/2024] Open
Abstract
For aging to evolve, selection against mortality must decrease with age. This prevailing view in the evolutionary theory of senescence posits that mutations with deleterious effects happening late in life-when purging selection is weak-may become fixed via genetic drift in the germline, and produce a senescent phenotype. Theory, however, has focused primarily on growing populations and the fate of single deleterious mutations. In a mathematical model, we demonstrate that relaxing both of these simplifying assumptions leads to unrealistic outcomes. In density-regulated populations, previously fixed deleterious mutations should promote the fixation of other deleterious mutations that lead to senescence at ever younger ages, until death necessarily occurs at sexual maturity. This sequential fixation of deleterious mutations is not promoted by a decrease in population size, but is due to a change in the strength of selection. In an individual-based model, we also show that such evolutionary dynamics should lead to the extinction of most populations. Our models therefore make rather unrealistic predictions, underlining the need for a reappraisal of current theories. In this respect, we have further assumed in our models that the deleterious effects of mutations can only occur at certain ages, marked, for instance, by somatic or physiological changes. Under this condition, we show that the catastrophic accumulation of deleterious mutations in the germline can stop. This new finding emphasizes the importance of investigating somatic factors, as well as other mechanisms underlying the deleterious effects of mutations, to understand senescence evolution. More generally, our model therefore establishes that patterns of senescence in nature depend not only on the decrease in selection strength with age but also on any mechanism that stops the catastrophic accumulation of mutations.
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Affiliation(s)
- Thomas G Aubier
- Laboratoire Évolution and Diversification Biologique, Université Paul Sabatier Toulouse III, UMR 5174, CNRS/IRD, 31077 Toulouse, France
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
| | - Matthias Galipaud
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
- Swiss Data Science Center, ETH, Zurich, Switzerland
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4
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Henske J, Eltz T. Age-dependent perfume development in male orchid bees, Euglossa imperialis. J Exp Biol 2024; 227:jeb246995. [PMID: 38511547 PMCID: PMC11006377 DOI: 10.1242/jeb.246995] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 02/24/2024] [Indexed: 03/22/2024]
Abstract
Male neotropical orchid bees concoct complex perfume blends by collecting exogenous volatiles from various sources, including orchids. These perfumes, stored in specialized hind-leg pouches and released during courtship, serve as inter-sexual signals. It has been hypothesized that male perfumes honestly indicate aspects of male fitness. If perfume traits such as quantity or complexity increase over individual lifetime, perfumes could reflect age (survival) and cumulative foraging success of males. We conducted a two-season mark-recapture study with Euglossa imperialis in Costa Rica, monitoring the balance of perfume uptake and expenditure over individual male lifetime. We sealed one hind-leg pouch upon initial capture, 'freezing' the perfume status on one side, and compared it with the other side at recapture to assess changes in perfume traits over time. Additionally, we used a novel method to estimate individual age by combining two parameters of wing degradation. Contrary to predictions, young to intermediate-aged bees had the highest quantities of perfume and the highest diversity of detected compounds. At the same time, the change in perfume between recaptures was positive (increase in amount and complexity) in young bees, whereas it was neutral to negative in older bees. Although these findings do not disprove an indicator function of male perfume, they shift the emphasis to non-cumulative fitness components such as sensory acuteness or cognitive capacity as likely targets of selection. Females preferring strong perfume signals in mates would maximize speed of foraging in offspring rather than their lifetime cumulative yield.
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Affiliation(s)
- Jonas Henske
- Department of Animal Ecology, Evolution and Biodiversity, Ruhr-Universität Bochum, 44801 Bochum, Germany
| | - Thomas Eltz
- Department of Animal Ecology, Evolution and Biodiversity, Ruhr-Universität Bochum, 44801 Bochum, Germany
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5
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Grosiak M, Koteja P, Hambly C, Speakman JR, Sadowska ET. Limits to sustained energy intake. XXXIV. Can the heat dissipation limit (HDL) theory explain reproductive aging? J Exp Biol 2024; 227:jeb246592. [PMID: 38264846 DOI: 10.1242/jeb.246592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 01/11/2024] [Indexed: 01/25/2024]
Abstract
According to the heat dissipation limit (HDL) theory, reproductive performance is limited by the capacity to dissipate excess heat. We tested the novel hypotheses that (1) the age-related decline in reproductive performance is due to an age-related decrease of heat dissipation capacity and (2) the limiting mechanism is more severe in animals with high metabolic rates. We used bank voles (Myodes glareolus) from lines selected for high swim-induced aerobic metabolic rate, which have also increased basal metabolic rate, and unselected control lines. Adult females from three age classes - young (4 months), middle-aged (9 months) and old (16 months) - were maintained at room temperature (20°C), and half of the lactating females were shaved to increase heat dissipation capacity. Old females from both selection lines had a decreased litter size, mass and growth rate. The peak-lactation average daily metabolic rate was higher in shaved than in unshaved mothers, and this difference was more profound among old than young and middle-aged voles (P=0.02). In females with large litters, milk production tended to be higher in shaved (least squares mean, LSM±s.e.: 73.0±4.74 kJ day-1) than in unshaved voles (61.8±4.78 kJ day-1; P=0.05), but there was no significan"t effect of fur removal on the growth rate [4.47±2.29 g (4 days-1); P=0.45]. The results provide mixed support of the HDL theory and no support for the hypotheses linking the differences in reproductive aging with either a deterioration in thermoregulatory capability or genetically based differences in metabolic rate.
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Affiliation(s)
- Marta Grosiak
- Institute of Environmental Sciences, Faculty of Biology, Jagiellonian University, Krakow 30-387, Poland
| | - Paweł Koteja
- Institute of Environmental Sciences, Faculty of Biology, Jagiellonian University, Krakow 30-387, Poland
| | - Catherine Hambly
- School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
| | - John R Speakman
- School of Biological Sciences, University of Aberdeen, Aberdeen AB24 2TZ, UK
- Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, People's Republic of China
| | - Edyta T Sadowska
- Institute of Environmental Sciences, Faculty of Biology, Jagiellonian University, Krakow 30-387, Poland
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Martín J, Rodríguez-Ruiz G, Navarro-Castilla Á, Barja I, López P. Blind date: female fossorial amphisbaenians prefer scent marks of large and healthy males. Integr Zool 2024. [PMID: 38247017 DOI: 10.1111/1749-4877.12802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2024]
Abstract
Selecting a good mate is a decision with important fitness consequences. For this reason, mate choice has promoted the evolution of sexual ornaments signaling the quality of an individual. In fossorial animals, inhabiting visually restricted underground environments, chemical senses should be very important for mate choice. We examined whether sexual chemical signals (substrate scent marks) produced by males of the Iberian worm lizard, Blanus cinereus, a strictly fossorial blind amphisbaenian, provide information to females on morphological traits and health state. We administered corticosterone (CORT) to males simulating a continuous stressor affecting their health. Females preferred settling at sites scent-marked by males in comparison with similar sites with female scent or unmarked sites, but the attractiveness of males' scent differed between individuals. Females preferred scent marks of larger/older males and with a higher immune response, while their body condition and CORT treatment were unrelated to female preferences. Chemical analyses showed that proportions of some compounds in precloacal secretions of males (used to produce scent marks) were correlated with the morphological (body size) and health state (immune response and body condition, but not CORT treatment) of these males. These results suggest that females may make site-selection decisions based on assessing the chemical characteristics of males' scent marks, which were reliably related to some of the traits of the male that produced the scent. Therefore, females might use chemical senses to increase the opportunities to find and mate with males of high quality, coping with the restrictions of the subterranean environment.
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Affiliation(s)
- José Martín
- Departmento de Ecología Evolutiva, Museo Nacional de Ciencias Naturales, CSIC, Madrid, Spain
| | - Gonzalo Rodríguez-Ruiz
- Departmento de Ecología Evolutiva, Museo Nacional de Ciencias Naturales, CSIC, Madrid, Spain
| | - Álvaro Navarro-Castilla
- Etho-Physiology Group, Unit of Zoology, Department of Biology, Faculty of Sciences, Autonomous University of Madrid, Madrid, Spain
- Centro de Investigación en Biodiversidad y Cambio Global (CIBC-UAM), Autonomous University of Madrid, Madrid, Spain
| | - Isabel Barja
- Etho-Physiology Group, Unit of Zoology, Department of Biology, Faculty of Sciences, Autonomous University of Madrid, Madrid, Spain
- Centro de Investigación en Biodiversidad y Cambio Global (CIBC-UAM), Autonomous University of Madrid, Madrid, Spain
| | - Pilar López
- Departmento de Ecología Evolutiva, Museo Nacional de Ciencias Naturales, CSIC, Madrid, Spain
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7
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Sanghvi K, Vega-Trejo R, Nakagawa S, Gascoigne SJL, Johnson SL, Salguero-Gómez R, Pizzari T, Sepil I. Meta-analysis shows no consistent evidence for senescence in ejaculate traits across animals. Nat Commun 2024; 15:558. [PMID: 38228708 PMCID: PMC10791739 DOI: 10.1038/s41467-024-44768-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Accepted: 01/04/2024] [Indexed: 01/18/2024] Open
Abstract
Male reproductive traits such as ejaculate size and quality, are expected to decline with advancing age due to senescence. It is however unclear whether this expectation is upheld across taxa. We perform a meta-analysis on 379 studies, to quantify the effects of advancing male age on ejaculate traits across 157 species of non-human animals. Contrary to predictions, we find no consistent pattern of age-dependent changes in ejaculate traits. This result partly reflects methodological limitations, such as studies sampling a low proportion of adult lifespan, or the inability of meta-analytical approaches to document non-linear ageing trajectories of ejaculate traits; which could potentially lead to an underestimation of senescence. Yet, we find taxon-specific differences in patterns of ejaculate senescence. For instance, older males produce less motile and slower sperm in ray-finned fishes, but larger ejaculates in insects, compared to younger males. Notably, lab rodents show senescence in most ejaculate traits measured. Our study challenges the notion of universal reproductive senescence, highlighting the need for controlled methodologies and a more nuanced understanding of reproductive senescence, cognisant of taxon-specific biology, experimental design, selection pressures, and life-history.
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Affiliation(s)
- Krish Sanghvi
- Department of Biology, University of Oxford, Oxford, UK.
| | | | - Shinichi Nakagawa
- Evolution and Ecology Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, Australia
| | | | - Sheri L Johnson
- Department of Zoology, University of Otago, Dunedin, New Zealand
| | | | | | - Irem Sepil
- Department of Biology, University of Oxford, Oxford, UK.
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8
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Scieszka D, Bolt AM, McCormick MA, Brigman JL, Campen MJ. Aging, longevity, and the role of environmental stressors: a focus on wildfire smoke and air quality. FRONTIERS IN TOXICOLOGY 2023; 5:1267667. [PMID: 37900096 PMCID: PMC10600394 DOI: 10.3389/ftox.2023.1267667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 09/25/2023] [Indexed: 10/31/2023] Open
Abstract
Aging is a complex biological process involving multiple interacting mechanisms and is being increasingly linked to environmental exposures such as wildfire smoke. In this review, we detail the hallmarks of aging, emphasizing the role of telomere attrition, cellular senescence, epigenetic alterations, proteostasis, genomic instability, and mitochondrial dysfunction, while also exploring integrative hallmarks - altered intercellular communication and stem cell exhaustion. Within each hallmark of aging, our review explores how environmental disasters like wildfires, and their resultant inhaled toxicants, interact with these aging mechanisms. The intersection between aging and environmental exposures, especially high-concentration insults from wildfires, remains under-studied. Preliminary evidence, from our group and others, suggests that inhaled wildfire smoke can accelerate markers of neurological aging and reduce learning capabilities. This is likely mediated by the augmentation of circulatory factors that compromise vascular and blood-brain barrier integrity, induce chronic neuroinflammation, and promote age-associated proteinopathy-related outcomes. Moreover, wildfire smoke may induce a reduced metabolic, senescent cellular phenotype. Future interventions could potentially leverage combined anti-inflammatory and NAD + boosting compounds to counter these effects. This review underscores the critical need to study the intricate interplay between environmental factors and the biological mechanisms of aging to pave the way for effective interventions.
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Affiliation(s)
- David Scieszka
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM, United States
| | - Alicia M. Bolt
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM, United States
| | - Mark A. McCormick
- Department of Biochemistry and Molecular Biology, School of Medicine, University of New Mexico Health Sciences Center, Albuquerque, NM, United States
| | - Jonathan L. Brigman
- Department of Neurosciences, School of Medicine, University of New Mexico Health Sciences Center, Albuquerque, NM, United States
| | - Matthew J. Campen
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico Health Sciences Center, Albuquerque, NM, United States
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9
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Martyka R, Arct A, Kotowska D, Gustafsson L. Age- and trait-dependent breeding responses to environmental variation in a short-lived songbird. Sci Rep 2023; 13:14967. [PMID: 37696936 PMCID: PMC10495331 DOI: 10.1038/s41598-023-42166-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2023] [Accepted: 09/06/2023] [Indexed: 09/13/2023] Open
Abstract
Breeding responses of organisms to environmental changes may profoundly depend on an individual's age, as an age-environment interaction may be expected to affect the expression of reproductive traits. However, little is known about how this interaction affects short-lived species that experience various environmental conditions in adulthood. Here, we used a 32-year dataset from the collared flycatcher, Ficedula albicollis, population to test whether and how the environment interacts with age to shape female age-specific reproduction. To characterise environmental variation, we applied the remotely sensed normalised difference vegetation index (NDVI), estimating vegetation productivity, and used it as a surrogate for habitat quality. Then, we analysed how within-individual age and NDVI determine patterns in laying date, clutch size, offspring production, and recruitment. We found that young and old females, but not middle-aged females, breeding under low NDVI started to lay eggs later and produced smaller clutches than females of the same age breeding under higher NDVI. No such effects were observed for offspring production or recruitment. Our study provides evidence that both an individual's age and the environmental variation experienced during adulthood may be crucial for shaping reproductive patterns in short-lived avian species, as has been found in long-lived birds.
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Affiliation(s)
- Rafał Martyka
- Animal Ecology, Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, 752 36, Uppsala, Sweden.
- Institute of Nature Conservation, Polish Academy of Sciences, Mickiewicza 33, 31-120, Kraków, Poland.
| | - Aneta Arct
- Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Sławkowska 17, 31-016, Kraków, Poland
| | - Dorota Kotowska
- Institute of Nature Conservation, Polish Academy of Sciences, Mickiewicza 33, 31-120, Kraków, Poland
| | - Lars Gustafsson
- Animal Ecology, Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, 752 36, Uppsala, Sweden
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10
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Morland F, Ewen JG, Simons MJP, Brekke P, Hemmings N. Early-life telomere length predicts life-history strategy and reproductive senescence in a threatened wild songbird. Mol Ecol 2023; 32:4031-4043. [PMID: 37173827 PMCID: PMC10947174 DOI: 10.1111/mec.16981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 03/20/2023] [Accepted: 04/21/2023] [Indexed: 05/15/2023]
Abstract
Telomeres are well known for their associations with lifespan and ageing across diverse taxa. Early-life telomere length can be influenced by developmental conditions and has been shown positively affect lifetime reproductive success in a limited number of studies. Whether these effects are caused by a change in lifespan, reproductive rate or perhaps most importantly reproductive senescence is unclear. Using long-term data on female breeding success from a threatened songbird (the hihi, Notiomystis cincta), we show that the early-life telomere length of individuals predicts the presence and rate of future senescence of key reproductive traits: clutch size and hatching success. In contrast, senescence of fledging success is not associated with early-life telomere length, which may be due to the added influence of biparental care at this stage. Early-life telomere length does not predict lifespan or lifetime reproductive success in this species. Females may therefore change their reproductive allocation strategy depending on their early developmental conditions, which we hypothesise are reflected in their early-life telomere length. Our results offer new insights on the role that telomeres play in reproductive senescence and individual fitness and suggest telomere length can be used as a predictor for future life history in threatened species.
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Affiliation(s)
- Fay Morland
- Department of BiosciencesUniversity of SheffieldSheffieldUK
- Institute of Zoology, Zoological Society of LondonLondonUK
- Department of AnatomyUniversity of OtagoDunedinNew Zealand
| | - John G. Ewen
- Institute of Zoology, Zoological Society of LondonLondonUK
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11
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McKenna-Ell C, Ravindran S, Pilkington JG, Pemberton JM, Nussey DH, Froy H. Trait-dependent associations between early- and late-life reproduction in a wild mammal. Biol Lett 2023; 19:20230050. [PMID: 37433328 DOI: 10.1098/rsbl.2023.0050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 06/23/2023] [Indexed: 07/13/2023] Open
Abstract
Early- versus late-life trade-offs are a central prediction of life-history theory that are expected to shape the evolution of ageing. While ageing is widely observed in wild vertebrates, evidence that early-late trade-offs influence ageing rates remains limited. Vertebrate reproduction is a complex, multi-stage process, yet few studies have examined how different aspects of early-life reproductive allocation shape late-life performance and ageing. Here, we use longitudinal data from a 36-year study of wild Soay sheep to show that early-life reproduction predicts late-life reproductive performance in a trait-dependent manner. Females that started breeding earlier showed more rapid declines in annual breeding probability with age, consistent with a trade-off. However, age-related declines in offspring first-year survival and birth weight were not associated with early-life reproduction. Selective disappearance was evident in all three late-life reproductive measures, with longer-lived females having higher average performance. Our results provide mixed support for early-late reproductive trade-offs and show that the way early-life reproduction shapes late-life performance and ageing can differ among reproductive traits.
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Affiliation(s)
- Chris McKenna-Ell
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK
| | - Sanjana Ravindran
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK
| | - Jill G Pilkington
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK
| | - Josephine M Pemberton
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK
| | - Daniel H Nussey
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK
| | - Hannah Froy
- Institute of Ecology and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, UK
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12
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McKee JL, Tompkins EM, Estela FA, Anderson DJ. Age effects on Nazca booby foraging performance are largely constant across variation in the marine environment: Results from a 5-year study in Galápagos. Ecol Evol 2023; 13:e10138. [PMID: 37304365 PMCID: PMC10253949 DOI: 10.1002/ece3.10138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 05/06/2023] [Accepted: 05/12/2023] [Indexed: 06/13/2023] Open
Abstract
Foraging outcomes dictate the nutritional resources available to an organism and may vary with intrinsic factors, like age. Thus, understanding how age affects foraging performance, alone or in interaction with extrinsic factors (like environmental quality), improves our understanding of aging processes in the wild. We examined how foraging traits, measured across five breeding seasons, change with age, environmental variation, and their interaction in Nazca boobies (Sula granti), a pelagic seabird in Galápagos. We evaluated the hypotheses that (1) foraging performance is better in middle-aged birds than in young ones, and that (2) foraging performance is better in middle-aged birds than in old ones. Furthermore, favorable environmental conditions will either (3) attenuate age differences in foraging performance (by relieving constraints on young, inexperienced and old, senescent age classes), or (4) accentuate age differences (if middle-aged birds can exploit abundant resources better than other age classes can). Incubating birds tagged with GPS loggers (N = 815) provided data on foraging performance (e.g., total distance traveled, mass gained) to evaluate interactions between age and environmental variation (e.g., sea surface temperature). Poor environmental conditions associated with the cool phase of the El Niño-Southern Oscillation increased foraging effort, including foraging distance and duration, for example. Across age classes, foraging boobies responded similarly to environmental variation except for female mass gain rate: age-related declines in mass gain rate were reduced under favorable environmental conditions. Birds of different ages also searched in somewhat distinct areas in the poor conditions of 2016, but not in other years. In several foraging traits, including foraging duration and distance, female boobies showed predicted early-life improvement and late-life decline, following the established pattern for reproductive traits in this species. Thus, deficits in resource acquisition (this study) may contribute to the poor survival and reproductive outcomes previously observed in old Nazca boobies, particularly in females.
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Affiliation(s)
- Jennifer L. McKee
- Department of BiologyWake Forest UniversityWinston‐SalemNorth CarolinaUSA
| | - Emily M. Tompkins
- Department of BiologyWake Forest UniversityWinston‐SalemNorth CarolinaUSA
| | - Felipe A. Estela
- Department of BiologyWake Forest UniversityWinston‐SalemNorth CarolinaUSA
- Departamento de Ciencias Naturales y MatemáticasPontificia Universidad Javeriana – CaliValle del CaucaColombia
| | - David J. Anderson
- Department of BiologyWake Forest UniversityWinston‐SalemNorth CarolinaUSA
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13
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Sorci G, Hussein HA, Levêque G, Saint Jalme M, Lacroix F, Hingrat Y, Lesobre L. Ranking parameters driving siring success during sperm competition in the North African houbara bustard. Commun Biol 2023; 6:305. [PMID: 36949210 PMCID: PMC10033649 DOI: 10.1038/s42003-023-04698-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 03/10/2023] [Indexed: 03/24/2023] Open
Abstract
Sperm competition is a powerful force driving the evolution of ejaculate and sperm traits. However, the outcome of sperm competition depends on many traits that extend beyond ejaculate quality. Here, we study male North African houbara bustards (Chlamydotis undulata undulata) competing for egg fertilization, after artificial insemination, with the aim to rank the importance of 14 parameters as drivers of siring success. Using a machine learning approach, we show that traits independent of male quality (i.e., insemination order, delay between insemination and egg laying) are the most important predictors of siring success. Traits describing intrinsic male quality (i.e., number of sperm in the ejaculate, mass motility index) are also positively associated with siring success, but their contribution to explaining the outcome of sperm competition is much lower than for insemination order. Overall, this analysis shows that males mating at the last position in the mating sequence have the best chance to win the competition for egg fertilization. This raises the question of the importance of female behavior as determinant of mating order.
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Affiliation(s)
- Gabriele Sorci
- Biogéosciences, UMR 6282 CNRS, Université de Bourgogne, Dijon, France.
| | - Hiba Abi Hussein
- Reneco International Wildlife Consultants LLC, Abu Dhabi, United Arab Emirates
| | | | - Michel Saint Jalme
- Centre d'Ecologie et des Sciences de la Conservation, CESCO, Museum National d'Histoire Naturelle, CNRS, Ménagerie le zoo du Jardin des Plantes, Sorbonne Université, Paris, France
| | - Frédéric Lacroix
- Reneco International Wildlife Consultants LLC, Abu Dhabi, United Arab Emirates
| | - Yves Hingrat
- Reneco International Wildlife Consultants LLC, Abu Dhabi, United Arab Emirates
| | - Loïc Lesobre
- Reneco International Wildlife Consultants LLC, Abu Dhabi, United Arab Emirates
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14
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Rotella JJ. Patterns, sources, and consequences of variation in age-specific vital rates: Insights from a long-term study of Weddell seals. J Anim Ecol 2023; 92:552-567. [PMID: 36495476 DOI: 10.1111/1365-2656.13870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Accepted: 12/06/2022] [Indexed: 12/14/2022]
Abstract
Variations in the reproductive and survival abilities of individuals within a population are ubiquitous in nature, key to individual fitness, and affect population dynamics, which leads to strong interest in understanding causes and consequences of vital-rate variation. For long-lived species, long-term studies of large samples of known-age individuals are ideal for evaluating vital-rate variation. A population of Weddell seals in Erebus Bay, Antarctica, has been studied each Austral spring since the 1960s. Since 1982, all newborns have been tagged each year and multiple capture-mark-recapture (CMR) surveys have been conducted annually. Over the past 20 years, a series of analyses have built on results of earlier research by taking advantage of steady improvements in the project's long-term CMR data and available analytical methods. Here, I summarize progress made on four major topics related to variation in age-specific vital rates for females: early-life survival and age at first reproduction, costs of reproduction, demographic buffering, and demographic senescence. Multistate modelling found that age at first reproduction varies widely (4-14 years of age) and identified contrasting influences of maternal age on survival and recruitment rates of offspring. Subsequent analyses of data for females after recruitment revealed costs of reproduction to both survival and future reproduction and provided strong evidence of demographic buffering. Recent results indicated that important levels of among-individual variation exist in vital rates and revealed contrasting patterns for senescence in reproduction and survival. Sources of variation in vital rates include age, reproductive state, year, and individual. The combination of luck and individual quality results in strong variation in individual fitness outcomes: ~80% of females born in the population produce no offspring, and the remaining 20% vary strongly in lifetime reproductive output (range: 1-23 pups). Further research is needed to identify the specific environmental conditions that lead to annual variation in vital rates and to better understand the origins of individual heterogeneity. Work is also needed to better quantify the relative roles of luck, maternal effects, and environmental conditions on variation in vital rates and to learn the importance of such variation to demographic performance of offspring and on overall population dynamics.
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Affiliation(s)
- Jay J Rotella
- Ecology Department, Montana State University, Bozeman, Montana, USA
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15
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Míčková K, Tomášek O, Jelínek V, Šulc M, Pazdera L, Albrechtová J, Albrecht T. Age-related changes in sperm traits and evidence for aging costs of sperm production in a sexually promiscuous passerine. Front Ecol Evol 2023. [DOI: 10.3389/fevo.2023.1105596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023] Open
Abstract
In many animal species, organismal performance declines with age in a process known as aging or senescence. Senescence typically leads to a deterioration of physiological functionality and can impact the development of primary sexual phenotypes. Sperm production is a complex and costly process that is sensitive to changes in individual physiological state, yet remarkably little is known about age-related changes in sperm performance and aging costs of sperm production. Here we use a non-linear generalized additive mixed models (GAMM) modelling to evaluate age-related changes in postcopulatory sexual traits in the European barn swallow (Hirundo rustica rustica), a relatively short lived sexually promiscuous passerine species, where male extra-pair fertilization success has been shown to increase with age. We confirmed a positive relationship between sperm midpiece length and sperm velocity in this species. Within-male changes in sperm morphology and sperm velocity were in general absent, with only sperm length decreasing linearly with increasing age, although this change was negligible compared to the overall variation in sperm size among males. In contrast, the cloacal protuberance (CP) size changed nonlinearly with age, with an initial increase between the first and third year of life followed by a plateau. The results further indicate the existence of a trade-off between investments in sperm production and survival as males with large CP tended to have a reduced lifespan. This seems consistent with the idea of expensive sperm production and survival aging costs associated with investments in post-copulatory traits in this sexually promiscuous species.
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16
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Riecke TV, Hegelbach J, Schaub M. Reproductive senescence and mating tactic interact and conflict to drive reproductive success in a passerine. J Anim Ecol 2023; 92:838-849. [PMID: 36708046 DOI: 10.1111/1365-2656.13893] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2022] [Accepted: 01/10/2023] [Indexed: 01/29/2023]
Abstract
An understanding of the drivers of individual fitness is a fundamental component of evolutionary ecology and life-history theory. Reproductive senescence, mate and mating tactic choice and latent heterogeneity in individual quality interact to affect individual fitness. We sought to disentangle the effects of these fitness drivers, where longitudinal data are required to understand their respective impacts. We used reproductive allocation and success data from a long-term (1989-2018) study of white-throated dippers Cinclus cinclus in Switzerland to simultaneously examine the effects of female and male age, mating tactic, nest initiation date and individual heterogeneity on reproductive performance. We modelled quadratic and categorical effects of age on reproductive parameters. The probability of polygyny increased with age in both sexes before declining in older age classes. Similarly, hatching probability in monogamous pairs and the number of nestlings hatched in both monogamous and polygynous pairs increased with female age before declining later in life. As predicted, offspring survival in monogamous pairs increased with male age before declining in older age classes, but male age had no effect on offspring survival in polygynous nesting attempts. Our results demonstrate that parental age, mating tactic and individual heterogeneity all affect reproductive success, and that the impacts of senescent decline are expressed across different demographic components as a function of sex-specific senescent decline and mating tactic.
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Affiliation(s)
| | - Johann Hegelbach
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
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17
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Vrtílek M, Žák J, Reichard M. Evidence for reproductive senescence across ray-finned fishes: A review. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.982915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The origin, incidence, and consequences of reproductive senescence vary greatly across the tree of life. In vertebrates, research on reproductive senescence has been mainly focused on mammals and birds, demonstrating that its variation is largely linked to critical life history traits, such as growth patterns, juvenile, and adult mortality, and reproductive strategy. Fishes represent half of the vertebrate taxonomic diversity and display remarkable variation in life history. Based on a thorough literature review, we summarize current evidence on reproductive senescence in ray-finned fishes (Actinopterygii). While survival and physiological senescence are acknowledged in fish, their potential age-related reproductive decline has often been disregarded due to the prevalence of indeterminate growth. We demonstrate that age-related reproductive decline is reported across fish phylogeny, environments, and traits. An important point of our review is that the incidence of reproductive senescence in a species depends on both the number of studies for that species and the coverage of its maximum lifespan by the study. Reproductive senescence was documented for one-third of the studied fish species, with females suffering an age-related decline in reproductive traits less often than males or both parents combined. Neither parental care nor migratory strategy corresponded with the occurrence of reproductive senescence in fish. The traits that were affected by reproductive senescence most often were sex-specific, with pre-mating and mating categories of traits declining in females and sperm quality and quantity in males. We also demonstrate that reproductive senescence can be buffered by indeterminate growth. We provide rich evidence of reproductive senescence across ray-finned fishes, but we highlight the need for better data on age-related reproduction in fishes.
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18
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Meunier L, Sorci G, Abi Hussein H, Hingrat Y, Rehspringer N, Saint-Jalme M, Lesobre L, Torres Carreira J. Pre-but not post-meiotic senescence affects sperm quality and reproductive success in the North African houbara bustard. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.977184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Age-dependent reduction in reproductive success can arise due to multiple factors including a deterioration of reproductive physiology. Senescing males have been shown to produce ejaculates with poor sperm quality, which impinges on male reproductive success. In addition to individual age, gamete age can also affect male reproductive success. Accordingly, variance in male reproductive success can be due to pre-meiotic (referring to individual age) and post-meiotic senescence (sperm age). Here, we tested whether male senescence and sperm cell aging have additive or interactive effects on male reproductive success in a bird with a promiscuous mating system, the North African houbara bustard. To assess the effect of pre-meiotic aging, we compared male reproductive success between two age classes (3-6- and 12–16-year-old). To infer the effect of post-meiotic aging, male ejaculates were collected at three-time intervals following a common initial collection (day 1, 5, and 10). Therefore, day 1 ejaculates are supposed to contain younger sperm than day 5 and 10 ejaculates. Following controlled artificial inseminations, reproductive success was assessed using three fitness-linked traits (hatching success, chick growth rate and survival). In addition to reproductive output, we also assessed whether pre- and post-meiotic aging affected a wide range of sperm and ejaculate traits. In agreement with previous reports, we found that males in the older age class produced less sperm with poorer motility compared to young individuals. However, contrary to the prediction, we found that ejaculates collected at day 5 and 10 tended to have better sperm traits such as motility and velocity. The results on sperm traits were generally mirrored in the effect on reproductive success since young males produced offspring that grew faster and had better survival during the first month of life, and eggs fertilized by sperm collected at day 5 had the highest hatching success. In any of the models, there was evidence for interactive effects of male and sperm age. Overall, these results confirm the role of pre-meiotic aging on male reproductive success. The lack of evidence for sperm aging could come from the experimental design but might also reflect the pattern of mating frequency in a species with a lek-based mating system.
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Park YH, Shin D, Han CS. Polyandrous females but not monogamous females vary in reproductive ageing patterns in the bean bug Riptortus pedestris. BMC Ecol Evol 2022; 22:115. [PMID: 36217117 PMCID: PMC9549660 DOI: 10.1186/s12862-022-02070-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Accepted: 09/27/2022] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND In general, reproductive performance exhibits nonlinear changes with age. Specifically, reproductive performance increases early in life, reaches a peak, and then declines later in life. Reproductive ageing patterns can also differ among individuals if they are influenced by individual-specific strategies of resource allocation between early-life reproduction and maintenance. In addition, the social environment, such as the number of available mates, can influence individual-specific resource allocation strategies and consequently alter the extent of individual differences in reproductive ageing patterns. That is, females that interact with more partners are expected to vary their copulation frequency, adopt a more flexible reproductive strategy and exhibit greater individual differences in reproductive ageing patterns. METHODS In this study, we evaluated the effect of mating with multiple males on both group- and individual-level reproductive ageing patterns in females of the bean bug Riptortus pedestris by ensuring that females experienced monogamous (one female with one male) or polyandrous conditions (one female with two males). RESULTS We found that group-level reproductive ageing patterns did not differ between monogamy-treatment and polyandry-treatment females. However, polyandry-treatment females exhibited among-individual variation in reproductive ageing patterns, while monogamy-treatment females did not. CONCLUSION Our findings provide the first empirical evidence regarding the influence of the social environment on individual variation in reproductive ageing patterns. We further suggest that the number of potential mates influences group- and individual-level reproductive ageing patterns, depending on which sex controls mating. We encourage future studies to consider interactions between species-specific mating systems and the social environment when evaluating group- and individual-level reproductive ageing patterns.
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Affiliation(s)
- Yi Hang Park
- grid.289247.20000 0001 2171 7818Department of Biology, Kyung Hee University, Seoul, Korea
| | - Donggyun Shin
- grid.289247.20000 0001 2171 7818Department of Biology, Kyung Hee University, Seoul, Korea
| | - Chang S. Han
- grid.289247.20000 0001 2171 7818Department of Biology, Kyung Hee University, Seoul, Korea
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20
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Naciri M, Aars J, Blanchet MA, Gimenez O, Cubaynes S. Reproductive senescence in polar bears in a variable environment. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.920481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Reproductive senescence is ubiquitous in mammals. However, patterns of senescence vary across reproductive traits, even within populations, perhaps because of differences in selection pressures, physiological constraints, and responses to environmental conditions. We investigated reproductive senescence in wild female polar bears (Ursus maritimus), using 31 years of capture-recapture data from the Svalbard area. We studied the influence of environmental conditions on age-specific litter production and litter size using generalized linear mixed models. Further, using a capture-recapture model that handles the dependency between vital rates of individuals belonging to the same family unit, we assessed maternal-age-related changes in first year cub and litter survival. We provide clear evidence for reproductive senescence in female polar bears. Litter production and litter size peaked in middle-aged females and declined sharply afterward. By contrast cub and litter survival did not decline after prime age. We found no evidence of terminal investment. The reproductive output of all females was affected by sea-ice conditions during the previous year and the Arctic Oscillation, with some effects differing greatly between age groups. Old females were affected the most by environmental conditions. Our results suggest that the decline in reproductive output is a combination of fertility and body-condition senescence, with a weak contribution of maternal-effect senescence, possibly due to benefits of experience. Further, as predicted by evolutionary theory, senescence appears to be a consequence of failures in early stages of the reproductive cycle rather than in late stages, and environmental variation affected old females more than prime-aged females. Our study emphasizes the need to study several reproductive traits and account for environmental variation when investigating reproductive senescence. Differences in senescence patterns across reproductive traits should be interpreted in light of evolutionary theory and while considering underlying physiological drivers.
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21
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Sex-specific effects of capital resources on reproductive timing and success in red squirrels. Behav Ecol Sociobiol 2022. [DOI: 10.1007/s00265-022-03245-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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22
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Genovart M, Klementisová K, Oro D, Fernández-López P, Bertolero A, Bartumeus F. Inferring the age of breeders from easily measurable variables. Sci Rep 2022; 12:15851. [PMID: 36151237 PMCID: PMC9508115 DOI: 10.1038/s41598-022-19381-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Accepted: 08/29/2022] [Indexed: 11/24/2022] Open
Abstract
Age drives differences in fitness components typically due to lower performances of younger and senescent individuals, and changes in breeding age structure influence population dynamics and persistence. However, determining age and age structure is challenging in most species, where distinctive age features are lacking and available methods require substantial efforts or invasive procedures. Here we explore the potential to assess the age of breeders, or at least to identify young and senescent individuals, by measuring some breeding parameters partially driven by age (e.g. egg volume in birds). Taking advantage of a long-term population monitored seabird, we first assessed whether age influenced egg volume, and identified other factors driving this trait by using general linear models. Secondly, we developed and evaluated a machine learning algorithm to assess the age of breeders using measurable variables. We confirmed that both younger and older individuals performed worse (less and smaller eggs) than middle-aged individuals. Our ensemble training algorithm was only able to distinguish young individuals, but not senescent breeders. We propose to test the combined use of field monitoring, classic regression analysis and machine learning methods in other wild populations were measurable breeding parameters are partially driven by age, as a possible tool for assessing age structure in the wild.
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Affiliation(s)
- Meritxell Genovart
- CEAB (CSIC), Carrer Accés Cala Sant Francesc, 14, 17300, Blanes, Catalonia, Spain. .,IMEDEA (CSIC-UIB), Miquel Marquès 21, 07190, Esporles, Balearic Islands, Spain.
| | | | - Daniel Oro
- CEAB (CSIC), Carrer Accés Cala Sant Francesc, 14, 17300, Blanes, Catalonia, Spain
| | - Pol Fernández-López
- CEAB (CSIC), Carrer Accés Cala Sant Francesc, 14, 17300, Blanes, Catalonia, Spain
| | - Albert Bertolero
- Associació Ornitològica Picampall de les Terres de l'Ebre, Amposta, Catalonia, Spain
| | - Frederic Bartumeus
- CEAB (CSIC), Carrer Accés Cala Sant Francesc, 14, 17300, Blanes, Catalonia, Spain.,CREAF, Cerdanyola del Vallès, 08193, Barcelona, Catalonia, Spain.,ICREA, Passeig Lluis Companys 23, 08010, Barcelona, Catalonia, Spain
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23
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Cope H, Ivimey-Cook ER, Moorad J. Triparental ageing in a laboratory population of an insect with maternal care. Behav Ecol 2022; 33:1123-1132. [DOI: 10.1093/beheco/arac078] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 07/13/2022] [Accepted: 08/08/2022] [Indexed: 11/13/2022] Open
Abstract
Abstract
Parental age at reproduction influences offspring size and survival by affecting prenatal and postnatal conditions in a wide variety of species, including humans. However, most investigations into this manifestation of ageing focus upon maternal age effects; the effects of paternal age and interactions between maternal and paternal age are often neglected. Furthermore, even when maternal age effects are studied, pre- and post-natal effects are often confounded. Using a cross-fostered experimental design, we investigated the joint effects of pre-natal paternal and maternal and post-natal maternal ages on five traits related to offspring outcomes in a laboratory population of a species of burying beetle, Nicrophorus vespilloides. We found a significant positive effect of the age of the egg producer on larval survival to dispersal. We found more statistical evidence for interaction effects, which acted on larval survival and egg length. Both interaction effects were negative and involved the age of the egg-producer, indicating that age-related pre-natal maternal improvements were mitigated by increasing age in fathers and foster mothers. These results agree with an early study that found little evidence for maternal senescence, but it emphasizes that parental age interactions may be an important contributor to ageing patterns. We discuss how the peculiar life history of this species may promote selection to resist the evolution of parental age effects, and how this might have influenced our ability to detect senescence.
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Affiliation(s)
- Hilary Cope
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh , Edinburgh , UK
| | - Edward R Ivimey-Cook
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh , Edinburgh , UK
| | - Jacob Moorad
- Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh , Edinburgh , UK
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24
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Kappeler PM, Pethig L, Prox L, Fichtel C. Reproductive Senescence in Two Lemur Lineages. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.894344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The relationship between age and reproductive performance is highly variable across species. Humans and some cetaceans exhibit an extreme form of reproductive senescence in that female reproduction ceases years or even decades before average life expectancy is reached. However, neither the existence of reproductive senescence in some taxa nor its absence in others is fully understood. Comparative data from other long-lived mammals may contribute to a more comprehensive understanding of the evolution of menopause, but data from wild primates, in particular, are scarce. We therefore investigated age-related female reproductive performance in two wild sympatric populations of Malagasy primates: Verreaux’s sifakas (Propithecus verreauxi) and redfronted lemurs (Eulemur rufifrons), which have a maximal longevity of more than 20 years. Based on 25 years of long-term demographic data, we extracted information on reproductive output of 38 female Verreaux’s sifakas and 42 female redfronted lemurs. We modeled variation in female reproductive performance and interbirth intervals as a function of age, the number of adult females within a group to account for female competition, and rainfall as a proxy for annual variation in food availability. We also compared our results for these two species with data on captive populations of the same two genera that are buffered from fluctuations in environmental variables. Our analyses disclosed statistical evidence for reproductive senescence in three out of four populations (captive Coquerel’s sifakas, wild redfronted lemurs, and captive red lemurs) but not for wild Verreaux’s sifakas. Compared to wild populations, reproductive senescence was therefore not less pronounced in captive animals, even though the latter are buffered from environmental adversities. In wild redfronted lemurs, mothers were more likely to give birth in years with more rainfall, but neither the number of co-resident females, nor annual rainfall did predict variation in the probability of giving birth in wild Verreaux’s sifakas. Thus, our study contributes valuable comparative information on reproductive senescence in a basal group of primates, and offers insights into the modulating effects of environmental, social and phylogenetic factors on patterns and dynamics of age-specific female reproduction.
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25
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Campos FA, Altmann J, Cords M, Fedigan LM, Lawler R, Lonsdorf EV, Stoinski TS, Strier KB, Bronikowski AM, Pusey AE, Alberts SC. Female reproductive aging in seven primate species: Patterns and consequences. Proc Natl Acad Sci U S A 2022; 119:e2117669119. [PMID: 35533284 PMCID: PMC9171789 DOI: 10.1073/pnas.2117669119] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 03/11/2022] [Indexed: 11/26/2022] Open
Abstract
Age-related changes in fertility have increasingly been documented in wild animal populations: In many species the youngest and oldest reproducers are disadvantaged relative to prime adults. How do these effects evolve, and what explains their diversity across species? Tackling this question requires detailed data on patterns of age-related reproductive performance in multiple animal species. Here, we compare patterns and consequences of age-related changes in female reproductive performance in seven primate populations that have been subjects of long-term continuous study for 29 to 57 y. We document evidence of age effects on fertility and on offspring performance in most, but not all, of these primate species. Specifically, females of six species showed longer interbirth intervals in the oldest age classes, youngest age classes, or both, and the oldest females also showed relatively fewer completed interbirth intervals. In addition, five species showed markedly lower survival among offspring born to the oldest mothers, and two species showed reduced survival for offspring born to both the youngest and the oldest mothers. In contrast, we found mixed evidence that maternal age affects the age at which daughters first reproduce: Only in muriquis and to some extent in chimpanzees, the only two species with female-biased dispersal, did relatively young mothers produce daughters that tended to have earlier first reproduction. Our findings demonstrate shared patterns as well as contrasts in age-related changes in female fertility across species of nonhuman primates and highlight species-specific behavior and life-history patterns as possible explanations for species-level differences.
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Affiliation(s)
- Fernando A. Campos
- Department of Anthropology, University of Texas at San Antonio, San Antonio, TX 78249
| | - Jeanne Altmann
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544
| | - Marina Cords
- Department of Ecology, Evolution, and Environmental Biology, Columbia University, New York, NY 10027
| | - Linda M. Fedigan
- Department of Anthropology, University of Calgary, Calgary, AB T2N 1N4, Canada
| | - Richard Lawler
- Department of Sociology and Anthropology, James Madison University, Harrisonburg, VA 22807
| | | | | | - Karen B. Strier
- Department of Anthropology, University of Wisconsin–Madison, Madison, WI 53706
| | - Anne M. Bronikowski
- Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011
| | - Anne E. Pusey
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27710
| | - Susan C. Alberts
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27710
- Department of Biology, Duke University, Durham, NC 27708
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26
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Dujon AM, Boutry J, Tissot S, Lemaître JF, Boddy AM, Gérard AL, Alvergne A, Arnal A, Vincze O, Nicolas D, Giraudeau M, Telonis-Scott M, Schultz A, Pujol P, Biro PA, Beckmann C, Hamede R, Roche B, Ujvari B, Thomas F. Cancer Susceptibility as a Cost of Reproduction and Contributor to Life History Evolution. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.861103] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Reproduction is one of the most energetically demanding life-history stages. As a result, breeding individuals often experience trade-offs, where energy is diverted away from maintenance (cell repair, immune function) toward reproduction. While it is increasingly acknowledged that oncogenic processes are omnipresent, evolving and opportunistic entities in the bodies of metazoans, the associations among reproductive activities, energy expenditure, and the dynamics of malignant cells have rarely been studied. Here, we review the diverse ways in which age-specific reproductive performance (e.g., reproductive aging patterns) and cancer risks throughout the life course may be linked via trade-offs or other mechanisms, as well as discuss situations where trade-offs may not exist. We argue that the interactions between host–oncogenic processes should play a significant role in life-history theory, and suggest some avenues for future research.
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27
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Raj Pant S, Versteegh MA, Hammers M, Burke T, Dugdale HL, Richardson DS, Komdeur J. The contribution of extra-pair paternity to the variation in lifetime and age-specific male reproductive success in a socially monogamous species. Evolution 2022; 76:915-930. [PMID: 35325482 PMCID: PMC9322416 DOI: 10.1111/evo.14473] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 01/29/2022] [Accepted: 02/13/2022] [Indexed: 01/21/2023]
Abstract
In socially monogamous species, extra-pair paternity (EPP) is predicted to increase variance in male reproductive success (RS) beyond that resulting from genetic monogamy, thus, increasing the "opportunity for selection" (maximum strength of selection that can act on traits). This prediction is challenging to investigate in wild populations because lifetime reproduction data are often incomplete. Moreover, age-specific variances in reproduction have been rarely quantified. We analyzed 21 years of near-complete social and genetic reproduction data from an insular population of Seychelles warblers (Acrocephalus sechellensis). We quantified EPP's contribution to lifetime and age-specific opportunities for selection in males. We compared the variance in male genetic RS vs social ("apparent") RS (RSap ) to assess if EPP increased the opportunity for selection over that resulting from genetic monogamy. Despite not causing a statistically significant excess (19%) of the former over the latter, EPP contributed substantially (27%) to the variance in lifetime RS, similarly to within-pair paternity (WPP, 39%) and to the positive WPP-EPP covariance (34%). Partitioning the opportunity for selection into age-specific (co)variance components, showed that EPP also provided a substantial contribution at most ages, varying with age. Therefore, despite possibly not playing the main role in shaping sexual selection in Seychelles warblers, EPP provided a substantial contribution to the lifetime and age-specific opportunity for selection, which can influence evolutionary processes in age-structured populations.
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Affiliation(s)
- Sara Raj Pant
- Groningen Institute for Evolutionary Life Sciences, Faculty of Science and EngineeringUniversity of GroningenGroningenThe Netherlands,Centre for Ecology, Evolution and Conservation, School of Biological SciencesUniversity of East Anglia, Norwich Research ParkNorwichUK,Department of BiologyLund UniversityLundSweden
| | - Maaike A. Versteegh
- Groningen Institute for Evolutionary Life Sciences, Faculty of Science and EngineeringUniversity of GroningenGroningenThe Netherlands
| | - Martijn Hammers
- Groningen Institute for Evolutionary Life Sciences, Faculty of Science and EngineeringUniversity of GroningenGroningenThe Netherlands,Aeres University of Applied SciencesAlmereThe Netherlands
| | - Terry Burke
- Department of Animal and Plant SciencesUniversity of SheffieldSheffieldUK
| | - Hannah L. Dugdale
- Groningen Institute for Evolutionary Life Sciences, Faculty of Science and EngineeringUniversity of GroningenGroningenThe Netherlands
| | - David S. Richardson
- Centre for Ecology, Evolution and Conservation, School of Biological SciencesUniversity of East Anglia, Norwich Research ParkNorwichUK,Nature SeychellesRoche CaimanMaheRepublic of Seychelles
| | - Jan Komdeur
- Groningen Institute for Evolutionary Life Sciences, Faculty of Science and EngineeringUniversity of GroningenGroningenThe Netherlands
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28
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When Older Males Sire More Offspring—Increased Attractiveness or Higher Fertility? Behav Ecol Sociobiol 2022; 76:61. [PMID: 35535127 PMCID: PMC9034975 DOI: 10.1007/s00265-022-03170-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 04/09/2022] [Accepted: 04/12/2022] [Indexed: 11/30/2022]
Abstract
Abstract
In birds with extrapair mating, older males usually have higher fertilization success than younger males. Two hypotheses can potentially explain this pattern: 1) females prefer older, and often more ornamented males, or 2) older males invest more in reproduction and fertility than younger males. Here we studied factors associated with age-related male fertilization success in a population of barn swallows Hirundo rustica in Canada. We document that male fertilization success increased gradually up to a minimum age of four-year old. The age effect was especially strong for the number of extrapair offspring obtained and the occurrence of a second brood. The higher fertilization success of older males was also associated with an early start of breeding in spring. The length of the elongated outermost tail feathers, a postulated male ornament preferred by females, also increased with age (in both sexes), but it was not a significant predictor of male fertilization success within age classes. Male fertility traits, especially testis size, but also sperm motility and sperm velocity, increased significantly across age groups. Our results suggest that the higher fertilization success by older males is due to their higher reproductive investments and that their longer tails are an adaptation to early arrival on the breeding grounds. Significance statement The barn swallow is a socially monogamous passerine with extensive extrapair mating. We found that males become more successful in siring both withinpair and extrapair offspring as they become older. Their increased fertilization success was associated with a higher reproductive effort as indicated by larger testes, more motile sperm, and an earlier start of breeding in spring. The length of the outer tail feathers increased with age in both sexes, but long tails did not enhance male fertilization success among males of the same age. Long tails are probably an adaptation to rapid migration and earlier arrival on the breeding grounds. Our findings suggest that the commonly observed age-related increase in male fertilization success in passerine birds is better explained by life history theory than by sexual selection theory. Supplementary Information The online version contains supplementary material available at 10.1007/s00265-022-03170-0.
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29
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Vedder O, Bichet C, Tschirren B. The Effect of Manipulated Prenatal Conditions on Growth, Survival, and Reproduction Throughout the Complete Life Course of a Precocial Bird. Front Ecol Evol 2022. [DOI: 10.3389/fevo.2022.834433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The quality of the environment individuals experience during development is commonly regarded as very influential on performance in later life. However, studies that have experimentally manipulated the early-life environment and subsequently measured individual performance in all components of fitness over the complete life course are scarce. In this study, we incubated fertile eggs of Japanese quail (Coturnix japonica) at substandard and standard incubation temperature, and monitored growth, survival, and reproduction throughout the complete life course. While embryonic development was slower and hatching success tended to be lower under substandard incubation temperature, the prenatal treatment had no effect on post-hatching growth, survival to sexual maturity, or age at first reproduction. In adulthood, body mass and investment in individual egg mass peaked at middle age, irrespective of the prenatal treatment. Individual reproduction rate declined soon after its onset, and was higher in females that lived longer. Yet, reproduction, and its senescence, were independent of the prenatal treatment. Similarly, adult survival over the complete lifespan was not affected. Hence, we did not find evidence for effects on performance beyond the developmental period that was manipulated. Our results suggest that effects of unfavorable developmental conditions on individual performance later in life could be negligible in some circumstances.
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30
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Paterson JT, Proffitt KM, Rotella JJ. Incorporating vital rates and harvest into stochastic population models to forecast elk population dynamics. J Wildl Manage 2022. [DOI: 10.1002/jwmg.22189] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
| | - Kelly M. Proffitt
- Montana Department of Fish, Wildlife, and Parks Bozeman 59718 MT USA
| | - Jay J. Rotella
- Montana State University 310 Lewis Hall Bozeman MT 59718 USA
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31
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Morosinotto C, Bensch S, Tarka M, Karell P. Heritability and parental effects in telomere length in a color polymorphic long-lived bird. Physiol Biochem Zool 2022; 95:350-364. [DOI: 10.1086/720161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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32
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Patrick SC, Réale D, Potts JR, Wilson AJ, Doutrelant C, Teplitsky C, Charmantier A. Differences in the temporal scale of reproductive investment across the slow-fast continuum in a passerine. Ecol Lett 2022; 25:1139-1151. [PMID: 35235709 PMCID: PMC9541748 DOI: 10.1111/ele.13982] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Revised: 01/07/2022] [Accepted: 01/12/2022] [Indexed: 11/29/2022]
Abstract
Life-history strategies differ with respect to investment in current versus 'future' reproduction, but when is this future? Under the novel 'temporality in reproductive investment hypothesis', we postulate variation should exist in the time frame over which reproductive costs are paid. Slow-paced individuals should pay reproductive costs over short (e.g. inter-annual) time scales to prevent reproductive costs accumulating, whereas fast-paced individuals should allow costs to accumulate (i.e. senescence). Using Fourier transforms, we quantify adjustments in clutch size with age, across four populations of blue tits (Cyanistes caeruleus). Fast populations had more prevalent and stronger long-term changes in reproductive investment, whereas slower populations had more prevalent short-term adjustments. Inter-annual environmental variation partly accounted for short-, but not long-term changes in reproductive investment. Our study reveals individuals differ in when they pay the cost of reproduction and that failure to partition this variation across different temporal scales and environments could underestimate reproductive trade-offs.
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Affiliation(s)
- Samantha C Patrick
- School of Environmental Sciences, University of Liverpool, Liverpool, UK
| | - Denis Réale
- Département des Sciences Biologiques, Université du Québec A Montréal, Québec, Canada
| | - Jonathan R Potts
- School of Mathematics and Statistics, University of Sheffield, Sheffield, UK
| | - Alastair J Wilson
- Centre for Ecology and Conservation, University of Exeter (Penryn Campus), Cornwall, UK
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33
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Barreaux AMG, Higginson AD, Bonsall MB, English S. Incorporating effects of age on energy dynamics predicts nonlinear maternal allocation patterns in iteroparous animals. Proc Biol Sci 2022; 289:20211884. [PMID: 35168397 PMCID: PMC8848239 DOI: 10.1098/rspb.2021.1884] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Iteroparous parents face a trade-off between allocating current resources to reproduction versus maximizing survival to produce further offspring. Parental allocation varies across age and follows a hump-shaped pattern across diverse taxa, including mammals, birds and invertebrates. This nonlinear allocation pattern lacks a general theoretical explanation, potentially because most studies focus on offspring number rather than quality and do not incorporate uncertainty or age-dependence in energy intake or costs. Here, we develop a life-history model of maternal allocation in iteroparous animals. We identify the optimal allocation strategy in response to stochasticity when energetic costs, feeding success, energy intake and environmentally driven mortality risk are age-dependent. As a case study, we use tsetse, a viviparous insect that produces one offspring per reproductive attempt and relies on an uncertain food supply of vertebrate blood. Diverse scenarios generate a hump-shaped allocation when energetic costs and energy intake increase with age and also when energy intake decreases and energetic costs increase or decrease. Feeding success and environmentally driven mortality risk have little influence on age-dependence in allocation. We conclude that ubiquitous evidence for age-dependence in these influential traits can explain the prevalence of nonlinear maternal allocation across diverse taxonomic groups.
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Affiliation(s)
- Antoine M G Barreaux
- School of Biological sciences, University of Bristol, Bristol BS8 1TQ, UK.,CIRAD, UMR INTERTRYP, F-34398 Montpellier, France.,INTERTRYP, Univ Montpellier, CIRAD, IRD, 34000 Montpellier, France
| | - Andrew D Higginson
- Centre for Research in Animal Behaviour, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QG, UK
| | - Michael B Bonsall
- Department of Zoology, Mathematical Ecology Research Group, University of Oxford, Oxford OX1 3PS, UK.,St Peters College, Oxford OX1 2DL, UK
| | - Sinead English
- School of Biological sciences, University of Bristol, Bristol BS8 1TQ, UK
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34
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Purchase CF, Rooke AC, Gaudry MJ, Treberg JR, Mittell EA, Morrissey MB, Rennie MD. A synthesis of senescence predictions for indeterminate growth, and support from multiple tests in wild lake trout. Proc Biol Sci 2022; 289:20212146. [PMID: 34982951 PMCID: PMC8727146 DOI: 10.1098/rspb.2021.2146] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Accepted: 12/06/2021] [Indexed: 01/14/2023] Open
Abstract
Senescence-the deterioration of functionality with age-varies widely across taxa in pattern and rate. Insights into why and how this variation occurs are hindered by the predominance of laboratory-focused research on short-lived model species with determinate growth. We synthesize evolutionary theories of senescence, highlight key information gaps and clarify predictions for species with low mortality and variable degrees of indeterminate growth. Lake trout are an ideal species to evaluate predictions in the wild. We monitored individual males from two populations (1976-2017) longitudinally for changes in adult mortality (actuarial senescence) and body condition (proxy for energy balance). A cross-sectional approach (2017) compared young (ages 4-10 years) and old (18-37 years) adults for (i) phenotypic performance in body condition, and semen quality-which is related to fertility under sperm competition (reproductive senescence)-and (ii) relative telomere length (potential proxy for cellular senescence). Adult growth in these particular populations is constrained by a simplified foodweb, and our data support predictions of negligible senescence when maximum size is only slightly larger than maturation size. Negative senescence (aka reverse senescence) may occur in other lake trout populations where diet shifts allow maximum sizes to greatly exceed maturation size.
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Affiliation(s)
- Craig F. Purchase
- Department of Biology, Memorial University of Newfoundland, St John's, Canada
| | - Anna C. Rooke
- Department of Biology, Memorial University of Newfoundland, St John's, Canada
| | - Michael J. Gaudry
- Department of Biological Sciences, University of Manitoba, Winnipeg, Canada
| | - Jason R. Treberg
- Department of Biological Sciences, University of Manitoba, Winnipeg, Canada
- Centre on Aging, University of Manitoba, Winnipeg, Canada
| | | | | | - Michael D. Rennie
- Department of Biology, Lakehead University, Thunder Bay, Canada
- IISD Experimental Lakes Area, Canada
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35
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Sorensen MC, Strickland D, Freeman NE, Fuirst M, Sutton AO, Norris DR. Early-life experience shapes patterns of senescence in a food-caching passerine. Biol Lett 2022; 18:20210532. [PMID: 35078329 PMCID: PMC8790376 DOI: 10.1098/rsbl.2021.0532] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Accepted: 12/14/2021] [Indexed: 01/28/2023] Open
Abstract
For many species, breeding performance increases through early adulthood followed by declines later in life. Although patterns of age-specific decline have been shown to vary between individuals, the factors that lead to this individual variation in the intensity of reproductive senescence are yet to be fully understood. We investigated whether early-life social status influenced age-related trends in the breeding performance of male Canada jays (Perisoreus canadensis), year-round residents of North America's boreal and sub-alpine forests. Shortly after young become nutritionally independent, intra-brood dominance struggles lead to one juvenile (Dominant Juvenile) remaining on the natal territory after expelling its subordinate siblings (Ejectees). First, we show via radio tracking that in our declining range-edge population Ejectees either join an unrelated pair (67%), form a breeding pair with another bird (28%) or occupy a territory alone (5%). Second, using 39 years of breeding data, we demonstrate that Ejectee males advanced laying dates and increased the annual number of nestlings until 6 years of age before declining, whereas Dominant Juvenile males advanced laying dates until 11 years and increased annual number of nestlings until 12 years of age before declining. This study documents clear variation in ageing patterns between dominant and expelled young, with implications for the role of early-life experiences and phenotypic quality in determining patterns of ageing.
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Affiliation(s)
- Marjorie C. Sorensen
- Department of Integrative Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Dan Strickland
- 1063 Oxtongue Lake Road, Dwight, Ontario P0A 1H0, Canada
| | - Nikole E. Freeman
- Department of Integrative Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Matthew Fuirst
- Department of Integrative Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Alex O. Sutton
- Department of Integrative Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - D. Ryan Norris
- Department of Integrative Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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36
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Roast MJ, Hidalgo Aranzamendi N, Teunissen N, Fan M, Verhulst S, Peters A. No Evidence for Constitutive Innate Immune Senescence in a Longitudinal Study of a Wild Bird. Physiol Biochem Zool 2021; 95:54-65. [PMID: 34870562 DOI: 10.1086/717937] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
AbstractAging is associated with declines in physiological performance; declining immune defenses particularly could have consequences for age-related fitness and survival. In aging vertebrates, adaptive (memory-based) immune responses typically become impaired, innate (nonspecific) responses undergo lesser declines, and inflammation increases. Longitudinal studies of immune functions in wild animals are rare, yet they are needed to understand immunosenescence under evolutionarily relevant conditions. Using longitudinal data from a tropical passerine (Malurus coronatus) population, we investigate how population trends emerge from within-individual changes and between-individual heterogeneity (e.g., selective disappearance) in immune status. We quantified constitutive immune indexes (haptoglobin [inflammation associated], natural antibodies, complement [lytic] activity, and heterophil-lymphocyte ratio; n=505-631) in individuals sampled one to seven times over 5 yr. Unexpectedly, longitudinal analyses showed no age-related change within individuals in any immune index, despite sufficient power to detect within-individual change. Between individuals, we found age-related declines in natural antibodies and increases in heterophil-lymphocyte ratios. However, selective disappearance could not adequately explain between-individual age effects, and longitudinal models could not explain our data better than cross-sectional analyses. The lack of clear within-individual immunosenescence is itself notable. Persistent levels of haptoglobin, complement activity, and natural antibodies into old age suggests that these immune components are maintained, potentially with adaptive significance.
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37
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Bichet C, Moiron M, Matson KD, Vedder O, Bouwhuis S. Immunosenescence in the wild? A longitudinal study in a long-lived seabird. J Anim Ecol 2021; 91:458-469. [PMID: 34850397 DOI: 10.1111/1365-2656.13642] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 11/18/2021] [Indexed: 01/03/2023]
Abstract
Longitudinal studies of various vertebrate populations have demonstrated senescent declines in reproductive performance and survival probability to be almost ubiquitous. Longitudinal studies of potential underlying proximate mechanisms, however, are still scarce. Due to its critical function in the maintenance of health and viability, the immune system is among the potential (mediators of) proximate mechanisms that could underlie senescence. Here, we studied three innate immune parameters-haemagglutination titre, haemolysis titre and haptoglobin concentration-in a population of common terns (Sterna hirundo) known to undergo actuarial senescence. We repeatedly sampled birds of known sex and age across 11 years and used random regression models to (a) quantify how immune parameters vary among individuals and (b) describe within-individual age-specific changes in, and potential trade-offs between, immune parameters. Our models revealed no differences between males and females in haemagglutination titre and haptoglobin concentration, and very low among-individual variation in these parameters in general. Within individuals, haemagglutination titre increased with age, while haptoglobin concentration did not change. We found no indication for selective (dis)appearance in relation to haemagglutination titre or haptoglobin concentration, nor for the existence of a trade-off between them. Haemolysis was absent in the majority (76%) of samples. Common terns do not exhibit clear senescence in haemagglutination titre and haptoglobin concentration and show very little among-individual variation in these parameters in general. This may be explained by canalisation of the immune parameters or by the colonial breeding behaviour of our study species, but more longitudinal studies are needed to facilitate investigation of links between species' characteristics and immunosenescence in wild animals.
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Affiliation(s)
- Coraline Bichet
- Institute of Avian Research, Wilhelmshaven, Germany.,Centre d'Etudes Biologiques de Chizé, CNRS-La Rochelle Université, UMR-7372, Villiers-en-Bois, France
| | - Maria Moiron
- Institute of Avian Research, Wilhelmshaven, Germany.,CEFE, Université de Montpellier, CNRS, EPHE, IRD, Université Paul Valéry Montpellier 3, Montpellier, France
| | - Kevin D Matson
- Wildlife Ecology and Conservation, Environmental Sciences Group, Wageningen University, Wageningen, The Netherlands
| | - Oscar Vedder
- Institute of Avian Research, Wilhelmshaven, Germany
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38
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Jacobs PJ, Hart DW, Suess T, Janse van Vuuren AK, Bennett NC. The Cost of Reproduction in a Cooperatively Breeding Mammal: Consequences of Seasonal Variation in Rainfall, Reproduction, and Reproductive Suppression. Front Physiol 2021; 12:780490. [PMID: 34867486 PMCID: PMC8640211 DOI: 10.3389/fphys.2021.780490] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Accepted: 11/01/2021] [Indexed: 12/31/2022] Open
Abstract
Biological investments, such as reproduction, are influenced by both biotic and abiotic factors and their interactions. The trade-off between reproduction and survival has been well established. Seasonally breeding species, therefore, may exhibit variations in these trade-offs, but there is a dearth of knowledge concerning this. This study investigated the physiological cost of reproduction (measured through oxidative stress) across seasons in the cooperatively breeding highveld mole-rat (Cryptomys hottentotus pretoriae), one of the few seasonal breeding mole-rats. Oxidative stress indicates elevated reactive oxygen species (ROS) levels, which can overwhelm antioxidant defences resulting in damaged proteins, lipids and DNA, which overall can reduce longevity and compromise reproduction. Oxidative markers such as total oxidant status (TOS-measure of total peroxides present), total antioxidant capacity (TAC), oxidative stress index (OSI), and malondialdehyde (MDA) are utilised to measure oxidative stress. In this study, breeding and non-breeding male (NBM) and female mole-rats were captured during the dry season (breeding period) and wet season (non-breeding period). There was an apparent cost of reproduction in the highveld mole-rat; however, the seasonality pattern to the cost of reproduction varied between the sexes. Breeding females (BFs) had significantly higher MDA during the breeding period/dry season in comparison to the non-breeding period/wet season; this is possibly a consequence of bearing and nursing offspring. Contrastingly, breeding males (BMs) showed increased oxidative damage in the non-breeding/wet season compared to the breeding/dry season, possibly due to increased activities of protecting their mating rights for the next breeding/dry season, but this was not significant. Interestingly, during the non-breeding period/wet season, non-breeding females (NBFs) are released from their reproductive suppression, which resulted in increases in TOS and OSI, which again indicated that just the mere ability to be able to breed results in a cost (oxidative stress). Therefore we can speculate that highveld mole-rats exhibited seasonal variation in redox balance brought about by variation in abiotic variables (e.g., rainfall), physiology and behaviour. We conclude that physiological changes associated with reproduction are sufficient to induce significant acute oxidative stress in the plasma of female highveld mole-rats, which become alleviated following transition to the non-breeding season/wet period suggesting a possible hormetic effect.
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39
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Lemaître JF, Rey B, Gaillard JM, Régis C, Gilot-Fromont E, Débias F, Duhayer J, Pardonnet S, Pellerin M, Haghani A, Zoller JA, Li CZ, Horvath S. DNA methylation as a tool to explore ageing in wild roe deer populations. Mol Ecol Resour 2021; 22:1002-1015. [PMID: 34665921 PMCID: PMC9297961 DOI: 10.1111/1755-0998.13533] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Revised: 09/24/2021] [Accepted: 10/11/2021] [Indexed: 12/12/2022]
Abstract
DNA methylation‐based biomarkers of ageing (epigenetic clocks) promise to lead to new insights into evolutionary biology of ageing. Relatively little is known about how the natural environment affects epigenetic ageing effects in wild species. In this study, we took advantage of a unique long‐term (>40 years) longitudinal monitoring of individual roe deer (Capreolus capreolus) living in two wild populations (Chizé and Trois‐Fontaines, France) facing different ecological contexts, to investigate the relationship between chronological age and levels of DNA methylation (DNAm). We generated novel DNA methylation data from n = 94 blood samples, from which we extracted leucocyte DNA, using a custom methylation array (HorvathMammalMethylChip40). We present three DNA methylation‐based estimators of age (DNAm or epigenetic age), which were trained in males, females, and both sexes combined. We investigated how sex differences influenced the relationship between DNAm age and chronological age using sex‐specific epigenetic clocks. Our results highlight that old females may display a lower degree of biological ageing than males. Further, we identify the main sites of epigenetic alteration that have distinct ageing patterns between the two sexes. These findings open the door to promising avenues of research at the crossroads of evolutionary biology and biogerontology.
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Affiliation(s)
- Jean-François Lemaître
- Laboratoire de Biométrie et Biologie Evolutive, UMR5558, Université de Lyon, Université Lyon 1, CNRS, Villeurbanne, France
| | - Benjamin Rey
- Laboratoire de Biométrie et Biologie Evolutive, UMR5558, Université de Lyon, Université Lyon 1, CNRS, Villeurbanne, France
| | - Jean-Michel Gaillard
- Laboratoire de Biométrie et Biologie Evolutive, UMR5558, Université de Lyon, Université Lyon 1, CNRS, Villeurbanne, France
| | - Corinne Régis
- Laboratoire de Biométrie et Biologie Evolutive, UMR5558, Université de Lyon, Université Lyon 1, CNRS, Villeurbanne, France
| | - Emmanuelle Gilot-Fromont
- Laboratoire de Biométrie et Biologie Evolutive, UMR5558, Université de Lyon, Université Lyon 1, CNRS, Villeurbanne, France.,Université de Lyon, VetAgro Sup, Marcy-l'Etoile, France
| | - François Débias
- Laboratoire de Biométrie et Biologie Evolutive, UMR5558, Université de Lyon, Université Lyon 1, CNRS, Villeurbanne, France
| | - Jeanne Duhayer
- Laboratoire de Biométrie et Biologie Evolutive, UMR5558, Université de Lyon, Université Lyon 1, CNRS, Villeurbanne, France
| | - Sylvia Pardonnet
- Laboratoire de Biométrie et Biologie Evolutive, UMR5558, Université de Lyon, Université Lyon 1, CNRS, Villeurbanne, France
| | - Maryline Pellerin
- Direction de la Recherche et de l'Appui Scientifique, Office Français de la Biodiversité, Unité Ongulés Sauvages, Gap, France
| | - Amin Haghani
- Human Genetics, David Geffen School of Medicine, University of California, Los Angeles California, USA
| | - Joseph A Zoller
- Department of Biostatistics, Fielding School of Public Health, University of California, Los Angeles, California, USA
| | - Caesar Z Li
- Department of Biostatistics, Fielding School of Public Health, University of California, Los Angeles, California, USA
| | - Steve Horvath
- Human Genetics, David Geffen School of Medicine, University of California, Los Angeles California, USA.,Department of Biostatistics, Fielding School of Public Health, University of California, Los Angeles, California, USA
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40
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Risely A, Wilhelm K, Clutton-Brock T, Manser MB, Sommer S. Diurnal oscillations in gut bacterial load and composition eclipse seasonal and lifetime dynamics in wild meerkats. Nat Commun 2021; 12:6017. [PMID: 34650048 PMCID: PMC8516918 DOI: 10.1038/s41467-021-26298-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Accepted: 09/29/2021] [Indexed: 12/27/2022] Open
Abstract
Circadian rhythms in gut microbiota composition are crucial for metabolic function, yet the extent to which they govern microbial dynamics compared to seasonal and lifetime processes remains unknown. Here, we investigate gut bacterial dynamics in wild meerkats (Suricata suricatta) over a 20-year period to compare diurnal, seasonal, and lifetime processes in concert, applying ratios of absolute abundance. We found that diurnal oscillations in bacterial load and composition eclipsed seasonal and lifetime dynamics. Diurnal oscillations were characterised by a peak in Clostridium abundance at dawn, were associated with temperature-constrained foraging schedules, and did not decay with age. Some genera exhibited seasonal fluctuations, whilst others developed with age, although we found little support for microbial senescence in very old meerkats. Strong microbial circadian rhythms in this species may reflect the extreme daily temperature fluctuations typical of arid-zone climates. Our findings demonstrate that accounting for circadian rhythms is essential for future gut microbiome research.
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Affiliation(s)
- Alice Risely
- Institute for Evolutionary Ecology and Conservation Genomics, Ulm, Germany.
| | - Kerstin Wilhelm
- Institute for Evolutionary Ecology and Conservation Genomics, Ulm, Germany
| | - Tim Clutton-Brock
- Large Animal Research Group, Department of Zoology, University of Cambridge, Cambridge, UK
- University of Pretoria, Mammal Research Institute, Pretoria, South Africa
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa
| | - Marta B Manser
- University of Pretoria, Mammal Research Institute, Pretoria, South Africa
- Kalahari Research Trust, Kuruman River Reserve, Northern Cape, South Africa
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Zurich, Switzerland
| | - Simone Sommer
- Institute for Evolutionary Ecology and Conservation Genomics, Ulm, Germany
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41
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Fernández-Eslava B, Alonso D, Alonso-Alvarez C. An age-related decline in the expression of a red carotenoid-based ornament in wild birds. Evolution 2021; 75:3142-3153. [PMID: 34643274 DOI: 10.1111/evo.14378] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 09/21/2021] [Accepted: 09/27/2021] [Indexed: 01/02/2023]
Abstract
The past decades have provided valuable information on how animals age in the wild. However, examples of male reproductive senescence are scarce. In particular, few studies have described an age-related decline in the expression of conspicuous traits influencing mating success. Red ornaments could be good candidates to detect this decline because their expression may depend on the availability of pigments (carotenoids) related to oxidative stress, the latter frequently linked to senescence. Furthermore, it has been argued that efficient mitochondrial metabolism is key to express red carotenoid-based ornaments, and mitochondrial dysfunction is usually associated with senescence. We studied the age-linked expression of a red carotenoid-based trait: the yellow-to-red plumage coloration of male common crossbills (Loxia curvirostra). This coloration has recently been experimentally related to mitochondrial function. Here, we analyzed longitudinal plumage coloration data obtained throughout 28 years in free-living birds. We detected an initial increase in redness during the first 2 years of life and a subsequent decline. The relationship between color and age was unrelated to within-individual body mass variability. As far as we know, this is the first demonstration of an age-related ketocarotenoid-based color decrease detected by simultaneously testing within- and between-individual variability in wild animals.
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Affiliation(s)
- B Fernández-Eslava
- Department of Environmental Biology, Universidad de Navarra, Pamplona, Spain
| | - D Alonso
- Department of Ornithology, Aranzadi Sciences Society, Donostia-S. Sebastián, Spain
| | - C Alonso-Alvarez
- Department of Evolutionary Ecology, Spanish National Research Council (CSIC), Madrid, Spain
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42
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Segami JC, Lind MI, Qvarnström A. Should females prefer old males? Evol Lett 2021; 5:507-520. [PMID: 34621537 PMCID: PMC8484724 DOI: 10.1002/evl3.250] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Revised: 07/01/2021] [Accepted: 07/12/2021] [Indexed: 12/05/2022] Open
Abstract
Whether females should prefer to mate with old males is controversial. Old males may sire offspring of low quality because of an aging germline, but their proven ability to reach an old age can also be an excellent indicator of superior genetic quality, especially in natural populations. These genetic effects are, however, hard to study in nature, because they are often confounded with direct benefits offered by old males to the female, such as experience and high territory quality. We, therefore, used naturally occurring extra‐pair young to disentangle different aspects of male age on female fitness in a natural population of collared flycatchers because any difference between within‐ and extra‐pair young within a nest should be caused by paternal genetic effects only. Based on 18 years of long‐term data, we found that females paired with older males as social partners experienced an overall reproductive advantage. However, offspring sired by old males were of lower quality as compared to their extra‐pair half‐siblings, whereas the opposite was found in nests attended by young males. These results imply a negative genetic effect of old paternal age, given that extra‐pair males are competitive middle‐age males. Thus, offspring may benefit from being sired by young males but raised by old males, to maximize both genetic and direct effects. Our results show that direct and genetic benefits from pairing with old males may act in opposing directions and that the quality of the germline may deteriorate before other signs of senescence become obvious.
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Affiliation(s)
- Julia Carolina Segami
- Department of Ecology and Genetics, Animal Ecology Uppsala University Uppsala SE-75236 Sweden
| | - Martin I Lind
- Department of Ecology and Genetics, Animal Ecology Uppsala University Uppsala SE-75236 Sweden
| | - Anna Qvarnström
- Department of Ecology and Genetics, Animal Ecology Uppsala University Uppsala SE-75236 Sweden
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43
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Lee DS, Kang YHR, Ruiz-Lambides AV, Higham JP. The observed pattern and hidden process of female reproductive trajectories across the life span in a non-human primate. J Anim Ecol 2021; 90:2901-2914. [PMID: 34541669 DOI: 10.1111/1365-2656.13590] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 09/07/2021] [Indexed: 11/30/2022]
Abstract
Age-specific fertility trajectories are fundamental to understanding population structure and the evolutionary ecology of diverse life histories. However, characterizing reproductive ageing has been difficult with cross-sectional data, where senescence especially late in life can be confounded by selective disappearance. Addressing such challenge requires longitudinal data tracking the reproductive life span of known individuals, but such data are rare, especially for very long-lived species such as primates. We analyse the entire life span trajectory of annual fertility, from reproductive maturity to death, for 673 free-ranging female rhesus macaques, Macaca mulatta, on Cayo Santiago, Puerto Rico. Using generalized linear mixed-effects models (GLMMs), we first tested if time to death explains the ageing pattern independently of and additionally to chronological age, and if so, whether there is interaction between them. While GLMM captures the patterns in the data well, it is not a generative model. For example, given the GLMM and an individual's reproductive trajectory up to a given age, we cannot directly predict the probability of reproduction or death in the next year. For this reason, we further fitted a hidden Markov chain model (HMM) which allows just such a prediction, and additionally helps infer the process underlying the observed trajectory. We show that, after accounting for individual differences in fertility, reproductive ageing exhibits both age-dependent decline and also an abrupt terminal decline independently of age at death. We infer from the HMM that the underlying process of reproductive trajectory is where individuals cycle between reproductive bouts until they enter an irreversible frail condition that constrains fertility. The findings provide valuable insights into the longitudinal progression of reproductive trajectories in primates, by revealing both age-dependent and age-independent patterns and processes of ageing, and contribute to a growing body of literature on reproductive ageing and senescence across animal taxa.
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Affiliation(s)
- D Susie Lee
- Population Health, Max-Planck-Institute for Demographic Research, Rostock, Germany.,Department of Anthropology, New York University, New York, NY, USA.,New York Consortium in Evolutionary Primatology, New York, NY, USA
| | - Yul H R Kang
- Department of Engineering, Cambridge University, Cambridge, UK
| | | | - James P Higham
- Department of Anthropology, New York University, New York, NY, USA.,New York Consortium in Evolutionary Primatology, New York, NY, USA
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44
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Pigeon G, Albon S, Loe LE, Bischof R, Bonenfant C, Forchhammer M, Irvine RJ, Ropstad E, Veiberg V, Stien A. Context-dependent fitness costs of reproduction despite stable body mass costs in an Arctic herbivore. J Anim Ecol 2021; 91:61-73. [PMID: 34543441 DOI: 10.1111/1365-2656.13593] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Accepted: 09/13/2021] [Indexed: 11/30/2022]
Abstract
The cost of reproduction on demographic rates is often assumed to operate through changing body condition. Several studies have found that reproduction depresses body mass more if the current conditions are severe, such as high population densities or adverse weather, than under benign environmental conditions. However, few studies have investigated the association between the fitness components and body mass costs of reproduction. Using 25 years of individual-based capture-recapture data from Svalbard reindeer Rangifer tarandus platyrhynchus, we built a novel Bayesian state-space model that jointly estimated interannual change in mass, annual reproductive success and survival, while accounting for incomplete observations. The model allowed us to partition the differential effects of intrinsic and extrinsic factors on both non-reproductive mass change and the body mass cost of reproduction, and to quantify their consequences on demographic rates. Contrary to our expectation, the body mass cost of reproduction (mean = -5.8 kg) varied little between years (CV = 0.08), whereas the between-year variation in body mass changes, that were independent of the previous year's reproductive state, varied substantially (CV = 0.4) in relation to autumn temperature and the amount of rain-on-snow in winter. This body mass loss led to a cost of reproduction on the next reproduction, which was amplified by the same environmental covariates, from a 10% reduction in reproductive success in benign years, to a 50% reduction in harsh years. The reproductive mass loss also resulted in a small reduction in survival. Our results show how demographic costs of reproduction, driven by interannual fluctuations in individual body condition, result from the balance between body mass costs of reproduction and body mass changes that are independent of previous reproductive state. We illustrate how a strong context-dependent fitness cost of reproduction can occur, despite a relatively fixed body mass cost of reproduction. This suggests that female reindeer display a very conservative energy allocation strategy, either aborting their reproductive attempt at an early stage or weaning at a relatively constant cost. Such a strategy might be common in species living in a highly stochastic and food limited environment.
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Affiliation(s)
- Gabriel Pigeon
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway
| | | | - Leif Egil Loe
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway
| | - Richard Bischof
- Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Ås, Norway
| | - Christophe Bonenfant
- UMR CNRS 5558, Laboratoire de Biométrie et Biologie Évolutive, Université de Lyon, Villeurbanne Cedex, France
| | | | | | - Erik Ropstad
- Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway
| | | | - Audun Stien
- Department for Arctic Ecology, Norwegian Institute for Nature Research, Fram Centre, Tromsø, Norway
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45
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Jacobs PJ, Hart DW, Bennett NC. Plasma oxidative stress in reproduction of two eusocial African mole-rat species, the naked mole-rat and the Damaraland mole-rat. Front Zool 2021; 18:45. [PMID: 34535150 PMCID: PMC8447654 DOI: 10.1186/s12983-021-00430-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Accepted: 09/02/2021] [Indexed: 12/11/2022] Open
Abstract
One of the most prominent life-history trade-offs involves the cost of reproduction. Oxidative stress has been proposed to be involved in this trade-off and has been associated with reduced life span. There is currently an unclear relationship between oxidative cost and the reproduction-longevity trade-off. The current study, using a non-lethal and minimally invasive (only a single blood sample and no euthanasia) method, investigated whether an oxidative cost (oxidative stress) to reproduction would be apparent in two long-lived eusocial mole-rats, the naked mole-rat (NMR), Heterocephalus glaber, and the Damaraland mole-rat (DMR), Fukomys damarensis, where breeding colony members live longer than non-breeder conspecifics. We measured the direct redox balance in plasma by measuring the oxidative stress index (OSI) based on the ratio of total oxidant status and total antioxidant activity in breeders and non-breeders of both sexes, in the two species. NMR had significantly higher OSI between breeders and non-breeders of each sex, whereas DMR showed no significant differences except for total antioxidant capacity (TAC). The mode of reproductive suppression and the degree of reproductive investment in NMR may explain to some degree the redox balance difference between breeders and non-breeders. DMR show minimal physiological changes between breeders and non-breeders except for the mode of reproduction, which may explain some variations in TAC and TOS values, but similar OSI between breeders and non-breeders.
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Affiliation(s)
- Paul Juan Jacobs
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, 0002, South Africa.
| | - Daniel William Hart
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, 0002, South Africa
| | - Nigel Charles Bennett
- Department of Zoology and Entomology, Mammal Research Institute, University of Pretoria, Pretoria, 0002, South Africa
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46
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Nimje PS, Mayer M, Zedrosser A, Sæbø M, Rosell F. Territory acquisition and mate choice in a monogamous mammal, the Eurasian beaver. Anim Behav 2021. [DOI: 10.1016/j.anbehav.2021.06.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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47
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Roper M, Capdevila P, Salguero-Gómez R. Senescence: why and where selection gradients might not decline with age. Proc Biol Sci 2021; 288:20210851. [PMID: 34284628 PMCID: PMC8292751 DOI: 10.1098/rspb.2021.0851] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Accepted: 06/30/2021] [Indexed: 12/19/2022] Open
Abstract
Patterns of ageing across the tree of life are much more diverse than previously thought. Yet, we still do not adequately understand how, why and where across the tree of life a particular pattern of ageing will evolve. An ability to predict ageing patterns requires a firmer understanding of how and why different ecological and evolutionary factors alter the sensitivity of fitness to age-related changes in mortality and reproduction. From this understanding, we can ask why and where selection gradients might not decline with age. Here, we begin by summarizing the recent breadth of literature that is unearthing, empirically and theoretically, the mechanisms that drive variation in patters of senescence. We focus on the relevance of two key parameters, population structure and reproductive value, as key to understanding selection gradients, and therefore senescence. We discuss how growth form, individual trade-offs, stage structure and social interactions may all facilitate differing distributions of these two key parameters than those predicted by classical theory. We argue that these four key aspects can help us understand why patterns of negligible and negative senescence can actually be explained under the same evolutionary framework as classical senescence.
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Affiliation(s)
- Mark Roper
- Department of Zoology, University of Oxford, 11a Mansfield Road, Oxford OX1 3SZ, UK
| | - Pol Capdevila
- Department of Zoology, University of Oxford, 11a Mansfield Road, Oxford OX1 3SZ, UK
- School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, UK
| | - Roberto Salguero-Gómez
- Department of Zoology, University of Oxford, 11a Mansfield Road, Oxford OX1 3SZ, UK
- Centre for Biodiversity and Conservation Science, University of Queensland, St Lucia, Queensland 4071, Australia
- Evolutionary Demography Laboratory, Max Plank Institute for Demographic Research, Rostock 18057, Germany
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48
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Tompkins EM, Anderson DJ. Breeding responses to environmental variation are age- and trait-dependent in female Nazca boobies. Ecology 2021; 102:e03457. [PMID: 34166542 DOI: 10.1002/ecy.3457] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Revised: 12/04/2020] [Accepted: 04/05/2021] [Indexed: 12/17/2022]
Abstract
Age and environment are important determinants of reproductive parameters in long-lived organisms. These factors may interact to determine breeding responses to environmental change, yet few studies have examined the environmental dependence of aging patterns across the entire life span. We do so, using a 20-yr longitudinal data set of reproductive phenotypes in long-lived female Nazca boobies (Sula granti), a monogamous seabird breeding in the eastern tropical Pacific. Young and old females may suffer from inexperience and senescence, respectively, and/or practice reproductive restraint. Breeding performance (for breeding participation, breeding date, clutch size, egg volume, and offspring production) was expected to be lower in these age classes, particularly under environmental challenge, in comparison with middle-aged breeders. Sea surface temperature anomalies (SSTA) represented interannual variation in the El Niño-Southern Oscillation (ENSO) and were one proxy for environmental quality (a population count of clutch initiations was a second). Although only females lay eggs, both sexes care for eggs and nestlings, and the male partner's age, alone or in interaction with female age, was evaluated as a predictor of breeding performance. Middle-aged females performed better than young and old birds for all reproductive traits. Pairing with a young male delayed breeding (particularly for old females) and reduced clutch size, and pairing with an old male reduced offspring production. Challenging environments increased age effects on breeding probability and breeding date across young to middle ages and for offspring production across middle to old ages. However, important exceptions to the predicted patterns for clutch size and fledging success across young to middle ages suggested that trade-offs between fitness components may complicate patterns of trait expression across the life span. Relationships between breeding participation, environment, and individual quality and/or experience in young females may also contribute to unexpected patterns for clutch size and fledging success, traits expressed only in breeders. Finally, independent of age, breeding responses of female Nazca boobies to the ENSO did not follow expectations derived from oceanic forcing of primary productivity. During El Niño-like conditions, egg-laying traits (clutch size, breeding date) improved, but offspring production declined, whereas La Niña-like conditions were "poor" environments throughout the breeding cycle.
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Affiliation(s)
- Emily M Tompkins
- Biology Department, Wake Forest University, Winston-Salem, North Carolina, USA
| | - David J Anderson
- Biology Department, Wake Forest University, Winston-Salem, North Carolina, USA
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Fay R, Ravussin PA, Arrigo D, von Rönn JAC, Schaub M. Age-specific reproduction in female pied flycatchers: evidence for asynchronous aging. Oecologia 2021; 196:723-734. [PMID: 34173894 PMCID: PMC8292251 DOI: 10.1007/s00442-021-04963-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 06/02/2021] [Indexed: 11/25/2022]
Abstract
Age-related variation in reproductive performance is central for the understanding of population dynamics and evolutionary processes. Our understanding of age trajectories in vital rates has long been limited by the lack of distinction between patterns occurring within- and among-individuals, and by the lack of comparative studies of age trajectories among traits. Thus, it is poorly understood how sets of demographic traits change within individuals according to their age. Based on 40 years of monitoring, we investigated age-related variation in five reproductive traits in female pied flycatchers (Ficedula hypoleuca) including laying date, clutch size, brood size, nest success (probability that a nest produces at least one chick) and egg success of successful nests (proportion of eggs resulting in a chick). We disentangled within- from among-individual processes and assessed the relative contribution of within-individual age-specific changes and selective appearance and disappearance. Finally, we compared the aging pattern among these five reproductive traits. We found strong evidence for age-specific performance including both early-life improvement and late-life decline in all reproductive traits but the egg success. Furthermore, the aging patterns varied substantially among reproductive traits both for the age of peak performance and for the rates of early-life improvement and late-life decline. The results show that age trajectories observed at the population level (cross-sectional analysis) may substantially differ from those occurring at the individual level and illustrate the complexity of variation in aging patterns across traits.
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Affiliation(s)
- Rémi Fay
- Swiss Ornithological Institute, Seerose 1, CH-6204, Sempach, Switzerland.
| | | | | | - Jan A C von Rönn
- Swiss Ornithological Institute, Seerose 1, CH-6204, Sempach, Switzerland
| | - Michael Schaub
- Swiss Ornithological Institute, Seerose 1, CH-6204, Sempach, Switzerland
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Aging as a consequence of selection to reduce the environmental risk of dying. Proc Natl Acad Sci U S A 2021; 118:2102088118. [PMID: 34031251 DOI: 10.1073/pnas.2102088118] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Each animal in the Darwinian theater is exposed to a number of abiotic and biotic risk factors causing mortality. Several of these risk factors are intimately associated with the act of energy acquisition as such and with the amount of reserve the organism has available from this acquisition for overcoming temporary distress. Because a considerable fraction of an individual's lifetime energy acquisition is spent on somatic maintenance, there is a close link between energy expenditure on somatic maintenance and mortality risk. Here, we show, by simple life-history theory reasoning backed up by empirical cohort survivorship data, how reduction of mortality risk might be achieved by restraining allocation to somatic maintenance, which enhances lifetime fitness but results in aging. Our results predict the ubiquitous presence of senescent individuals in a highly diverse group of natural animal populations, which may display constant, increasing, or decreasing mortality with age. This suggests that allocation to somatic maintenance is primarily tuned to expected life span by stabilizing selection and is not necessarily traded against reproductive effort or other traits. Due to this ubiquitous strategy of modulating the somatic maintenance budget so as to increase fitness under natural conditions, it follows that individuals kept in protected environments with very low environmental mortality risk will have their expected life span primarily defined by somatic damage accumulation mechanisms laid down by natural selection in the wild.
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