1
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Collins DH, Prince DC, Donelan JL, Chapman T, Bourke AFG. Costs of reproduction are present but latent in eusocial bumblebee queens. BMC Biol 2023; 21:153. [PMID: 37430246 DOI: 10.1186/s12915-023-01648-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Accepted: 06/12/2023] [Indexed: 07/12/2023] Open
Abstract
BACKGROUND The standard evolutionary theory of ageing proposes that ageing occurs because of a trade-off between reproduction and longevity. Eusocial insect queens exhibit positive fecundity-longevity associations and so have been suggested to be counter-examples through not expressing costs of reproduction and through remodelling conserved genetic and endocrine networks regulating ageing and reproduction. If so, eusocial evolution from solitary ancestors with negative fecundity-longevity associations must have involved a stage at which costs of reproduction were suppressed and fecundity and longevity became positively associated. Using the bumblebee (Bombus terrestris), we experimentally tested whether queens in annual eusocial insects at an intermediate level of eusocial complexity experience costs of reproduction, and, using mRNA-seq, the extent to which they exhibit a remodelling of relevant genetic and endocrine networks. Specifically, we tested whether costs of reproduction are present but latent, or whether a remodelling of relevant genetic and endocrine networks has already occurred allowing queens to reproduce without costs. RESULTS We experimentally increased queens' costs of reproduction by removing their eggs, which caused queens to increase their egg-laying rate. Treatment queens had significantly reduced longevity relative to control queens whose egg-laying rate was not increased. Reduced longevity in treatment queens was not caused by increased worker-to-queen aggression or by increased overall activity in queens. In addition, treatment and control queens differed in age-related gene expression based on mRNA-seq in both their overall expression profiles and the expression of ageing-related genes. Remarkably, these differences appeared to occur principally with respect to relative age, not chronological age. CONCLUSIONS This study represents the first simultaneously phenotypic and transcriptomic experimental test for a longevity cost of reproduction in eusocial insect queens. The results support the occurrence of costs of reproduction in annual eusocial insects of intermediate social complexity and suggest that reproductive costs are present but latent in queens of such species, i.e. that these queens exhibit condition-dependent positive fecundity-longevity associations. They also raise the possibility that a partial remodelling of genetic and endocrine networks underpinning ageing may have occurred in intermediately eusocial species such that, in unmanipulated conditions, age-related gene expression depends more on chronological than relative age.
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Affiliation(s)
- David H Collins
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK.
| | - David C Prince
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Jenny L Donelan
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Tracey Chapman
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
| | - Andrew F G Bourke
- School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich, NR4 7TJ, UK
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2
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Rodrigues MA, Merckelbach A, Durmaz E, Kerdaffrec E, Flatt T. Transcriptomic evidence for a trade-off between germline proliferation and immunity in Drosophila. Evol Lett 2021; 5:644-656. [PMID: 34917403 PMCID: PMC8645197 DOI: 10.1002/evl3.261] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2021] [Revised: 09/07/2021] [Accepted: 09/12/2021] [Indexed: 11/08/2022] Open
Abstract
Life-history theory posits that investment into reproduction might occur at the expense of investment into somatic maintenance, including immune function. If so, reduced or curtailed reproductive effort might be expected to increase immunity. In support of this notion, work in Caenorhabditis elegans has shown that worms lacking a germline exhibit improved immunity, but whether the antagonistic relation between germline proliferation and immunity also holds for other organisms is less well understood. Here, we report that transgenic ablation of germ cells in late development or early adulthood in Drosophila melanogaster causes elevated baseline expression and increased induction of Toll and Imd immune genes upon bacterial infection, as compared to fertile flies with an intact germline. We also identify immune genes whose expression after infection differs between fertile and germline-less flies in a manner that is conditional on their mating status. We conclude that germline activity strongly impedes the expression and inducibility of immune genes and that this physiological trade-off might be evolutionarily conserved.
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Affiliation(s)
| | | | - Esra Durmaz
- Department of BiologyUniversity of FribourgCH‐1700 FribourgSwitzerland
| | - Envel Kerdaffrec
- Department of BiologyUniversity of FribourgCH‐1700 FribourgSwitzerland
| | - Thomas Flatt
- Department of BiologyUniversity of FribourgCH‐1700 FribourgSwitzerland
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3
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Lindsay WR, Friesen CR, Sihlbom C, Bergström J, Berger E, Wilson MR, Olsson M. Vitellogenin offsets oxidative costs of reproduction in female painted dragon lizards. J Exp Biol 2020; 223:jeb221630. [PMID: 32393548 DOI: 10.1242/jeb.221630] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Accepted: 05/05/2020] [Indexed: 12/18/2022]
Abstract
Vitellogenesis ('yolking' of follicles) is a bioenergetically costly stage of reproduction requiring enlargement of the liver to produce vitellogenin (VTG) yolk precursor proteins, which are transported and deposited at the ovary. VTG may, however, serve non-nutritive anti-oxidant functions, a hypothesis supported by empirical work on aging and other life-history transitions in several taxa. We test this hypothesis in female painted dragon lizards (Ctenophorus pictus) by examining covariation in VTG with the ovarian cycle, and relative to reactive oxygen species (ROS) including baseline superoxide (bSO). Plasma VTG decreased prior to ovulation, when VTG is deposited into follicles. VTG, however, remained elevated post-ovulation when no longer necessary for yolk provisioning and was unrelated to reproductive investment. Instead, VTG was strongly and positively predicted by prior bSO. ROS, in turn, was negatively predicted by prior VTG, while simultaneously sampled VTG was a positive predictor. These findings are consistent with the hypothesis that VTG functions as an anti-oxidant to counteract oxidative stress associated with vitellogenesis. The relationship between bSO and VTG was strongest in post-ovulatory females, indicating that its function may be largely anti-oxidant at this time. In conclusion, VTG may be under selection to offset oxidative costs of reproduction in egg-producing species.
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Affiliation(s)
- Willow R Lindsay
- Department of Biological and Environmental Sciences, University of Gothenburg, SE 405 30 Gothenburg, Sweden
| | - Christopher R Friesen
- School of Chemistry and Molecular Bioscience and Molecular Horizons Research Institute, The University of Wollongong, Wollongong, NSW 2522, Australia
| | - Carina Sihlbom
- Proteomics Core Facility of Sahlgrenska Academy, University of Gothenburg, SE 405 30 Gothenburg, Sweden
| | - Jörgen Bergström
- Proteomics Core Facility of Sahlgrenska Academy, University of Gothenburg, SE 405 30 Gothenburg, Sweden
| | - Evelin Berger
- Proteomics Core Facility of Sahlgrenska Academy, University of Gothenburg, SE 405 30 Gothenburg, Sweden
| | - Mark R Wilson
- School of Chemistry and Molecular Bioscience and Molecular Horizons Research Institute, The University of Wollongong, Wollongong, NSW 2522, Australia
- Illawarra Health and Medical Research Institute, Wollongong, NSW 2522, Australia
| | - Mats Olsson
- Department of Biological and Environmental Sciences, University of Gothenburg, SE 405 30 Gothenburg, Sweden
- School of Chemistry and Molecular Bioscience and Molecular Horizons Research Institute, The University of Wollongong, Wollongong, NSW 2522, Australia
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4
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Pick JL, Hatakeyama M, Ihle KE, Gasparini J, Haussy C, Ishishita S, Matsuda Y, Yoshimura T, Kanaoka MM, Shimizu-Inatsugi R, Shimizu KK, Tschirren B. Artificial selection reveals the role of transcriptional constraints in the maintenance of life history variation. Evol Lett 2020; 4:200-211. [PMID: 32547781 PMCID: PMC7293072 DOI: 10.1002/evl3.166] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 01/23/2020] [Accepted: 02/18/2020] [Indexed: 11/06/2022] Open
Abstract
The trade-off between reproduction and self-maintenance is a cornerstone of life history theory, yet its proximate underpinnings are elusive. Here, we used an artificial selection approach to create replicated lines of Japanese quail (Coturnix japonica) that differ genetically in their reproductive investment. Whole transcriptome sequencing revealed that females from lines selected for high reproductive output show a consistent upregulation of genes associated with reproduction but a simultaneous downregulation of immune genes. Concordant phenotypic differences in immune function (i.e., specific antibody response against keyhole limpet hemocyanin) were observed between the selection lines, even in males who do not provide parental care. Our findings demonstrate the key role of obligate transcriptional constraints in the maintenance of life history variation. These constraints set fundamental limits to productivity and health in natural and domestic animal populations.
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Affiliation(s)
- Joel L Pick
- Department of Evolutionary Biology and Environmental Studies University of Zurich Zurich 8057 Switzerland.,School of Biological, Earth and Environmental Sciences University of New South Wales Sydney Australia.,Current Address: Institute of Evolutionary Biology University of Edinburgh Edinburgh United Kingdom
| | - Masaomi Hatakeyama
- Department of Evolutionary Biology and Environmental Studies University of Zurich Zurich 8057 Switzerland.,Functional Genomics Center Zurich Zurich 8057 Switzerland
| | - Kate E Ihle
- Department of Evolutionary Biology and Environmental Studies University of Zurich Zurich 8057 Switzerland
| | - Julien Gasparini
- Laboratoire Ecologie and Evolution UMR 7625 Université Pierre et Marie Curie CNRS ENS Paris France
| | - Claudy Haussy
- Laboratoire Ecologie and Evolution UMR 7625 Université Pierre et Marie Curie CNRS ENS Paris France
| | - Satoshi Ishishita
- Graduate School of Bioagricultural Sciences Nagoya University Nagoya 464-8602 Japan
| | - Yoichi Matsuda
- Graduate School of Bioagricultural Sciences Nagoya University Nagoya 464-8602 Japan
| | - Takashi Yoshimura
- Graduate School of Bioagricultural Sciences Nagoya University Nagoya 464-8602 Japan
| | | | - Rie Shimizu-Inatsugi
- Department of Evolutionary Biology and Environmental Studies University of Zurich Zurich 8057 Switzerland
| | - Kentaro K Shimizu
- Department of Evolutionary Biology and Environmental Studies University of Zurich Zurich 8057 Switzerland.,Kihara Institute for Biological Research Yokohama City University Yokohama 244-0813 Japan
| | - Barbara Tschirren
- Centre for Ecology and Conservation University of Exeter Penryn TR10 9FE United Kingdom
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5
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Gale TJ, Garratt M, Brooks RC. Female mice seek refuge from castrated males, but not intact or vasectomized males, mitigating a socially-induced glucocorticoid response. Physiol Behav 2019; 211:112678. [PMID: 31505190 DOI: 10.1016/j.physbeh.2019.112678] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2019] [Revised: 08/07/2019] [Accepted: 09/05/2019] [Indexed: 10/26/2022]
Abstract
Sexual conflict may be manifested during social interactions, shaping the costs of reproduction in sexually reproducing species. This conflict, and the physical necessity of intromission, can intensify the already costly nature of reproduction for female mammals. To identify and partition the costs that males inflict on females during mating and reproduction, we paired female mice with either other females or castrated, vasectomised, or intact (sham-vasectomised) males, thus manipulating exposure to social mating behavior and costs arising from fertilization. We also provided females with refuges where males could not enter, to test whether females show avoidance or attraction to males of different gonadal status expected to exhibit different levels of social behavior. We found that females paired with vasectomised and castrated males spent the most time in their refuge. Females housed with castrated males also had increased glucocorticoid levels, an effect that was mitigated when females could retreat from these males to a refuge. This suggests that females actively refuge from castrated males, and that housing with such males is sufficient to generate an increased glucocorticoid response. Our results show that females choose to refuge from males depending on the partner's gonadal status, choices that are linked to social induced stress responses but not exposure to male mating behaviour.
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Affiliation(s)
- Teagan J Gale
- Evolution & Ecology Research Centre, School of Biological, Earth and Environmental Sciences (BEES), the University of New South Wales, High Street, Kensington, NSW 2052, Australia.
| | - Michael Garratt
- Evolution & Ecology Research Centre, School of Biological, Earth and Environmental Sciences (BEES), the University of New South Wales, High Street, Kensington, NSW 2052, Australia; Department of Anatomy, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Robert C Brooks
- Evolution & Ecology Research Centre, School of Biological, Earth and Environmental Sciences (BEES), the University of New South Wales, High Street, Kensington, NSW 2052, Australia
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6
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Andrew JR, Garland T, Chappell MA, Zhao M, Saltzman W. Effects of short- and long-term cold acclimation on morphology, physiology, and exercise performance of California mice (Peromyscus californicus): potential modulation by fatherhood. J Comp Physiol B 2019; 189:471-487. [PMID: 31073767 PMCID: PMC6667301 DOI: 10.1007/s00360-019-01219-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 03/27/2019] [Accepted: 04/22/2019] [Indexed: 01/23/2023]
Abstract
California mice (Peromyscus californicus) differ from most other mammals in that they are biparental, genetically monogamous, and (compared with other Peromyscus) relatively large. We evaluated effects of cold acclimation on metabolic rate, exercise performance, and morphology of pair-housed male California mice, as well as modulation of these effects by fatherhood. In Experiment 1, virgin males housed at 5° or 10 °C for approximately 25 days were compared with virgins housed at standard vivarium temperature of 22 °C. Measures included resting metabolic rate (RMR), maximal oxygen consumption ([Formula: see text]max), grip strength, and sprint speed. In Experiment 2, virgin males housed at 22 °C were compared with three groups of males housed at 10 °C: virgins, breeding males (housed with a female and their pups), and non-breeding males (housed with an ovariectomized, estrogen- and progesterone-treated female) after long-term acclimation (mean 243 days). Measures in this experiment included basal metabolic rate (BMR), [Formula: see text]max, maximal thermogenic capacity ([Formula: see text]sum), and morphological traits. In Experiment 1, virgin males housed at 5° and 10 °C had higher RMR and [Formula: see text]max than those at 22 °C. In Experiment 2, 10 °C-acclimated groups had shorter bodies; increased body, fat, and lean masses; higher BMR and [Formula: see text]sum, and generally greater morphometric measures and organ masses than virgin males at 22 °C. Among the groups housed at 10 °C, breeding males had higher BMR and lower [Formula: see text]max than non-breeding and/or virgin males. Overall, we found that effects of fatherhood during cold acclimation were inconsistent, and that several aspects of cold acclimation differ substantially between California mice and other small mammals.
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Affiliation(s)
- Jacob R Andrew
- Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, Riverside, CA, 92521, USA
- Department of Obstetrics, Gynecology and Reproductive Sciences, Moores Cancer Center, University of California, San Diego, La Jolla, CA, 92037, USA
| | - Theodore Garland
- Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, Riverside, CA, 92521, USA
| | - Mark A Chappell
- Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, Riverside, CA, 92521, USA
| | - Meng Zhao
- Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, Riverside, CA, 92521, USA
- Department of Pathology, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Wendy Saltzman
- Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, Riverside, CA, 92521, USA.
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7
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Roddy AB, van Blerk JJ, Midgley JJ, West AG. Ramification has little impact on shoot hydraulic efficiency in the sexually dimorphic genus Leucadendron (Proteaceae). PeerJ 2019; 7:e6835. [PMID: 31179169 PMCID: PMC6545101 DOI: 10.7717/peerj.6835] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 03/22/2019] [Indexed: 11/20/2022] Open
Abstract
Despite the diversity of branching architectures in plants, the impact of this morphological variation on hydraulic efficiency has been poorly studied. Branch junctions are commonly thought to be points of high hydraulic resistance, but adjustments in leaf area or xylem conduit abundance or dimensions could compensate for the additional hydraulic resistance of nodal junctions at the level of the entire shoot. Here we used the sexually dimorphic genus Leucadendron (Proteaceae) to test whether variation in branch ramification impacts shoot hydraulic efficiency. We found that branch ramification was related to leaf traits via Corner’s rules such that more highly ramified shoots had smaller leaves, but that branch ramification had little consistent impact on shoot hydraulic efficiency, whether measured on a leaf area or stem cross-sectional area basis. These results suggest that the presumed increase in resistance associated with branching nodes can be compensated by other adjustments at the shoot level (e.g. leaf area adjustments, increased ramification to add additional branches in parallel rather than in series) that maintain hydraulic efficiency at the level of the entire shoot. Despite large morphological differences between males and females in the genus Leucadendron, which are due to differences in pollination and reproduction between the sexes, the physiological differences between males and females are minimal.
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Affiliation(s)
- Adam B Roddy
- Department of Integrative Biology, University of California, Berkeley, Berkeley, CA, United States of America
| | | | - Jeremy J Midgley
- Biological Sciences, University of Cape Town, Cape Town, South Africa
| | - Adam G West
- Biological Sciences, University of Cape Town, Cape Town, South Africa
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8
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Abstract
Parental care is assumed to be costly in that it requires sustained, high-intensity activity sufficient to cause costs of reproduction (decreased survival and future fecundity of parents). Costs of reproduction are, in turn, thought to have a physiological basis where intense activity causes a decrease in parental condition. However, attempts to identify the physiological basis of costs of reproduction have produced mixed results. Here, I argue that in birds, the central idea that parental care represents sustained, high-intensity work might be incorrect. Specifically: (a) the duration of intense activity associated with chick-rearing might be quite limited; (b) flight, the most obvious sustained, high-intensity activity, might only represent a small component of an individual's overall activity budget; (c) some (high-quality) individuals might be able to tolerate costs of intense activity, either owing to their physiological state or because they have access to more resources, without perturbation of physiological homeostasis; and (d) individuals might utilise other mechanisms to modulate costs of activity, for example, mass loss, again avoiding more substantial physiological costs. Furthermore, I highlight the important fact that life-history theory predicts that reproductive trade-offs should only be expected under food stress. Most birds breed in spring and early summer precisely because of seasonal increases in food abundance, and so it is unclear how often parents are food stressed. Consequently, I argue that there are many reasons why costs of reproduction, and any physiological signature of these costs, might be quite rare, both temporally (in different years) and among individuals.
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Affiliation(s)
- Tony D Williams
- Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada V5A 1S6
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9
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Kindsvater HK, Braun DC, Otto SP, Reynolds JD. Costs of reproduction can explain the correlated evolution of semelparity and egg size: theory and a test with salmon. Ecol Lett 2016; 19:687-96. [PMID: 27146705 DOI: 10.1111/ele.12607] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2015] [Revised: 03/07/2016] [Accepted: 03/18/2016] [Indexed: 11/30/2022]
Abstract
Species' life history traits, including maturation age, number of reproductive bouts, offspring size and number, reflect adaptations to diverse biotic and abiotic selection pressures. A striking example of divergent life histories is the evolution of either iteroparity (breeding multiple times) or semelparity (breed once and die). We analysed published data on salmonid fishes and found that semelparous species produce larger eggs, that egg size and number increase with salmonid body size among populations and species and that migratory behaviour and parity interact. We developed three hypotheses that might explain the patterns in our data and evaluated them in a stage-structured modelling framework accounting for different growth and survival scenarios. Our models predict the observation of small eggs in iteroparous species when egg size is costly to maternal survival or egg number is constrained. By exploring trait co-variation in salmonids, we generate new hypotheses for the evolution of trade-offs among life history traits.
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Affiliation(s)
- Holly K Kindsvater
- Earth to Ocean Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
| | - Douglas C Braun
- School of Resource and Environmental Management, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada.,InStream Fisheries Research Inc., Vancouver, British Columbia, V5M 4V8, Canada
| | - Sarah P Otto
- Biodiversity Research Centre, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
| | - John D Reynolds
- Earth to Ocean Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada
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10
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Fletcher QE, Dantzer B, Boonstra R. The impact of reproduction on the stress axis of free-living male northern red backed voles (Myodes rutilus). Gen Comp Endocrinol 2015; 224:136-47. [PMID: 26188715 DOI: 10.1016/j.ygcen.2015.07.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Revised: 07/05/2015] [Accepted: 07/14/2015] [Indexed: 11/29/2022]
Abstract
Activation of the hypothalamic-pituitary-adrenal (HPA) axis culminates in the release of glucocorticoids (henceforth CORT), which have wide-reaching physiological effects. Three hypotheses potentially explain seasonal variation in CORT. The enabling hypothesis predicts that reproductive season CORT exceeds post-reproductive season CORT because CORT enables reproductive investment. The inhibitory hypothesis predicts the opposite because CORT can negatively affect reproductive function. The costs of reproduction hypothesis predicts that HPA axis condition declines over and following the reproductive season. We tested these hypotheses in wild male red-backed voles (Myodes rutilus) during the reproductive and post-reproductive seasons. We quantified CORT levels in response to restraint stress tests consisting of three blood samples (initial, stress-induced, and recovery). Mineralocorticoid (MR) and glucocorticoid (GR) receptor mRNA levels in the brain were also quantified over the reproductive season. Total CORT (tCORT) in the initial and stress-induced samples were greater in the post-reproductive than in the reproductive season, which supported the inhibitory hypothesis. Conversely, free CORT (fCORT) did not differ between the reproductive and post-reproductive seasons, which was counter to both the enabling and inhibitory hypotheses. Evidence for HPA axis condition decline in CORT as well as GR and MR mRNA over the reproductive season (i.e. costs of reproduction hypothesis) was mixed. Moreover, all of the parameters that showed signs of declining condition over the reproductive season did not also show signs of declining condition over the post-reproductive season suggesting that the costs resulting from reproductive investment had subsided. In conclusion, our results suggest that different aspects of the HPA axis respond differently to seasonal changes and reproductive investment.
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Affiliation(s)
- Quinn E Fletcher
- Centre for the Neurobiology Stress, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada.
| | - Ben Dantzer
- Department of Psychology, University of Michigan, Ann Arbor, MI 48109, USA; Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA.
| | - Rudy Boonstra
- Centre for the Neurobiology Stress, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada.
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11
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Niewiarowski PH, Dunham AE. EFFECTS OF MORTALITY RISK AND GROWTH ON A MODEL OF REPRODUCTIVE EFFORT: WHY THE SHINE AND SCHWARZKOPF MODEL IS NOT GENERAL. Evolution 1998; 52:1236-1241. [PMID: 28565212 DOI: 10.1111/j.1558-5646.1998.tb01852.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/1997] [Accepted: 04/23/1998] [Indexed: 11/30/2022]
Abstract
Using data and reanalysis of a model published by Shine and Schwarzkopf (1992) we reject the two unsubstantiated assertions made by Shine et al. (1996) about modeling the evolution of reproductive effort in squamate reptiles: (1) mortality schedules do not affect predictions of the Shine and Schwarzkopf (1992) model; and (2) growth rates that would affect the predictions of the original model are biologically unreasonable. On the basis of these two points alone, we strongly reject Shine et al.'s (1996) claim that a critique by Niewiarowski and Dunham (1994) actually reinforces the original conclusions of Shine and Schwarzkopf (1992). Furthermore, results and data presented here are strong enough to severely circumscribe the generality of the Shine and Schwarzkopf (1992) model. Though we do not provide data or new analyses of the potential effects of offspring size variation, we reaffirm the position of Niewiarowski and Dunham (1994) that the sensitivity of the Shine and Schwarzkopf (1992) model to such effects should be explored before using it as a basis for structuring future research on the evolution of reproductive effort in squamate reptiles.
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Affiliation(s)
| | - Arthur E Dunham
- Department of Biology, Leidy Labs, University of Pennsylvania, Philadelphia, Pennsylvania, 19104
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12
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Shine R, Schwarzkopf L, Caley MJ. ENERGY, RISK, AND REPTILIAN REPRODUCTIVE EFFORT: A REPLY TO NIEWIAROWSKI AND DUNHAM. Evolution 1996; 50:2111-2114. [PMID: 28565605 DOI: 10.1111/j.1558-5646.1996.tb03599.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/1995] [Accepted: 12/26/1995] [Indexed: 11/26/2022]
Affiliation(s)
- R Shine
- School of Biological Sciences A08, University of Sydney, New South Wales, 2006, Australia
| | - L Schwarzkopf
- Department of Zoology, James Cook University, Townsville, Queensland, 4811, Australia
| | - M J Caley
- Department of Marine Biology, James Cook University, Townsville, Queensland, 4811, Australia
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