1
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Lee NLY, Kuan PSY, Hua QQH, Puniamoorthy N. Experimental evolution under predation reduces body size in dung flies but courtship displays persist in males (Diptera: Sepsidae). Behav Processes 2024; 220:105073. [PMID: 38917938 DOI: 10.1016/j.beproc.2024.105073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Revised: 06/14/2024] [Accepted: 06/17/2024] [Indexed: 06/27/2024]
Abstract
Exaggerated sexual traits, such as ornaments and courtship displays, are crucial for mate acquisition in many species and are often subject to directional runaway selection. However, in the face of high predation risk, natural selection can result in a reduction of conspicuous precopulatory displays to avoid detection by potential predators. Sexual selection may then favour increased investment in inconspicuous postcopulatory traits. Here, we investigated the transgenerational effects of predation on precopulatory male courtship and postcopulatory sexual traits (testes size, sperm length) in a dung fly, Sepsis punctum (Sepsidae). Behavioural assays prior to selection document a marked decrease in male courtship displays in the presence of a predator, the Asian Ant Mantis (Odontomantis planiceps). However, after ten generations of experimental evolution, flies exhibited a marked increase in courtship, both in the absence and presence of a predator. Additionally, under sustained predation pressure, male and female body size decreased but male postcopulatory traits were not significantly affected. These results suggest that precopulatory courtship can be under strong sexual selection even in the face of predation pressure. Larger flies were more susceptible to predation, and there could be canalisation of postcopulatory traits that are crucial for fertilisation.
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Affiliation(s)
- Nicole L Y Lee
- Department of Biological Sciences, National University of Singapore, 16 Science Drive 4, Singapore 117558, Singapore
| | - Pamela S Y Kuan
- National Cancer Centre Singapore, 11 Hospital Crescent 169610, Singapore
| | - Qiaz Q H Hua
- Department of Ecology and Evolution, University of Adelaide, 115 Darling, North Terrace Campus, Adelaide, South Australia 5005, Australia
| | - Nalini Puniamoorthy
- Department of Biological Sciences, National University of Singapore, 16 Science Drive 4, Singapore 117558, Singapore.
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2
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Somjee U, Marting P, Anzaldo S, Simmons LW, Painting CJ. Extreme range in adult body size reveals hidden trade-offs among sexually selected traits. Evolution 2024; 78:1382-1395. [PMID: 38900629 DOI: 10.1093/evolut/qpae084] [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: 11/25/2023] [Revised: 05/13/2024] [Accepted: 05/24/2024] [Indexed: 06/22/2024]
Abstract
Sexually selected weapons used to monopolize mating opportunities are predicted to trade-off with traits used in competition for fertilization. Yet, the limited size range typically found among adults of a species often precludes clear comparisons between population-level and individual-level relative trait investment. The jousting weevil, Brentus anchorago (Coleoptera: Brentidae), varies more than 26-fold in body mass, which is among the most extreme adult body size ranges of any solitary terrestrial species. We reveal a trade-off at a population level: hypermetric scaling in male weapons (slope = 1.59) and a closely mirrored reversal in allocation to postcopulatory traits (slope = 0.54). Yet, at the individual level, we find the opposite pattern; males that invest relatively more in weapons for their size class also invest more in postcopulatory traits. Across 36 dung beetle and 41 brentine weevil species, we find the allometric slope explains more trait variation at larger body size ranges; in brentines, population-level scaling patterns become more detectable in species with a larger range in adult body size. Our findings reveal that population-level allometries and individual-level trade-offs can both be important in shaping relative trait allocation; we highlight that the adult body size range is rarely examined but may be integral to gaining a deeper understanding of trade-offs in reproductive allocation.
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Affiliation(s)
- Ummat Somjee
- Department of Integrative Biology, University of Texas, Austin, TX, United States
- Smithsonian Tropical Research Institute, Balboa, Panama
| | - Peter Marting
- Department of Biological Sciences, Auburn University, Auburn, AL, United States
| | - Salvatore Anzaldo
- School of Life Sciences, Arizona State University, Tempe, AZ, United States
| | - Leigh W Simmons
- School of Biological Sciences, University of Western Australia, Perth, WA, Australia
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3
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Yu G, Wong BH, Painting CJ, Li H, Yu L, Zhang Z, Zhang S, Li D. Males armed with big weapons win fights at limited cost in ant-mimicking jumping spiders. Curr Zool 2024; 70:98-108. [PMID: 38476142 PMCID: PMC10926263 DOI: 10.1093/cz/zoac101] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Accepted: 12/18/2022] [Indexed: 03/14/2024] Open
Abstract
A core assumption of sexual selection theory is that sexually selected weapons, specialized morphological structures used directly in male contests, can improve an individual's reproductive success but only if the bearer can overcome associated costs, the negative effects on the bearer's fitness components. However, recent studies have shown that producing and wielding exaggerated weapons may not necessarily be costly. Rather, some traits can be selected for supporting, or compensating for, the expense of producing and wielding such exaggerated weapons. In the ant-mimicking jumping spider Myrmarachne gisti, exaggerated chelicerae are borne only by adult males and not females, showing sexual dimorphism and steep positive allometry with body size. Here, we determine the potential benefits of bearing exaggerated chelicerae during male contests and explore the potential for costs in terms of prey-capture efficiency and compensation between chelicera size and neighboring trait size. While males with longer chelicerae won most of their male-male contests, we found no significant differences in prey-capture efficiency between males and females regardless of whether prey was winged or flightless. Males' elongated chelicerae thus do not impede their efficiency at capturing prey. Furthermore, we found that the sizes of all neighboring traits are positively correlated with chelicera size, suggesting that these traits may be under correlational selection. Taken together, our findings suggest that M. gisti males armed with the exaggerated chelicerae that function as weapons win more fights at limited cost for performance in prey capture and compensate for neighboring structures.
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Affiliation(s)
- Guocheng Yu
- State Key Laboratory of Biocatalysis and Enzyme Engineering and Centre for Behavioral Ecology and Evolution, School of Life Sciences, Hubei University, Wuhan 430062, China
| | - Boon Hui Wong
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore
| | - Christina J Painting
- Te Aka Mātuatua School of Science, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand
| | - Hongze Li
- State Key Laboratory of Biocatalysis and Enzyme Engineering and Centre for Behavioral Ecology and Evolution, School of Life Sciences, Hubei University, Wuhan 430062, China
| | - Long Yu
- State Key Laboratory of Biocatalysis and Enzyme Engineering and Centre for Behavioral Ecology and Evolution, School of Life Sciences, Hubei University, Wuhan 430062, China
| | - Zengtao Zhang
- State Key Laboratory of Biocatalysis and Enzyme Engineering and Centre for Behavioral Ecology and Evolution, School of Life Sciences, Hubei University, Wuhan 430062, China
| | - Shichang Zhang
- State Key Laboratory of Biocatalysis and Enzyme Engineering and Centre for Behavioral Ecology and Evolution, School of Life Sciences, Hubei University, Wuhan 430062, China
| | - Daiqin Li
- Department of Biological Sciences, National University of Singapore, 14 Science Drive 4, Singapore 117543, Singapore
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4
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Morbiato E, Cattelan S, Pilastro A, Grapputo A. Sperm production is negatively associated with muscle and sperm telomere length in a species subjected to strong sperm competition. Mol Ecol 2023; 32:5812-5822. [PMID: 37792396 DOI: 10.1111/mec.17158] [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: 03/10/2023] [Revised: 08/29/2023] [Accepted: 09/20/2023] [Indexed: 10/05/2023]
Abstract
Life-history theory suggests that ageing is one of the costs of reproduction. Accordingly, a higher reproductive allocation is expected to increase the deterioration of both the somatic and the germinal lines through enhanced telomere attrition. In most species, males' reproductive allocation mainly regards traits that increase mating and fertilization success, that is sexually selected traits. In this study, we tested the hypothesis that a higher investment in sexually selected traits is associated with a reduced relative telomere length (RTL) in the guppy (Poecilia reticulata), an ectotherm species characterized by strong pre- and postcopulatory sexual selection. We first measured telomere length in both the soma and the sperm over guppies' lifespan to see whether there was any variation in telomere length associated with age. Second, we investigated whether a greater investment in pre- and postcopulatory sexually selected traits is linked to shorter telomere length in both the somatic and the sperm germinal lines, and in young and old males. We found that telomeres lengthened with age in the somatic tissue, but there was no age-dependent variation in telomere length in the sperm cells. Telomere length in guppies was significantly and negatively correlated with sperm production in both tissues and life stages considered in this study. Our findings indicate that telomere length in male guppies is strongly associated with their reproductive investment (sperm production), suggesting that a trade-off between reproduction and maintenance is occurring at each stage of males' life in this species.
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Affiliation(s)
- Elisa Morbiato
- Department of Biology, University of Padova, Padova, Italy
| | - Silvia Cattelan
- Department of Biology, University of Padova, Padova, Italy
- Fritz Lipmann Institute - Leibniz Institute on Aging, Jena, Germany
| | - Andrea Pilastro
- Department of Biology, University of Padova, Padova, Italy
- National Biodiversity Future Center, Palermo, Italy
| | - Alessandro Grapputo
- Department of Biology, University of Padova, Padova, Italy
- National Biodiversity Future Center, Palermo, Italy
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5
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Powell EC, Painting CJ, Machado G, Holwell GI. Juvenile leg autotomy predicts adult male morph in a New Zealand harvestman with weapon polymorphism. Behav Ecol 2023; 34:613-620. [PMID: 37434639 PMCID: PMC10332453 DOI: 10.1093/beheco/arad029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2022] [Revised: 03/08/2023] [Accepted: 03/29/2023] [Indexed: 07/13/2023] Open
Abstract
Intraspecific weapon polymorphisms that arise via conditional thresholds may be affected by juvenile experience such as predator encounters, yet this idea has rarely been tested. The New Zealand harvestman Forsteropsalis pureora has three male morphs: majors (alphas and betas) are large-bodied with large chelicerae used in male-male contests, while minors (gammas) are small-bodied with small chelicerae and scramble to find mates. Individuals use leg autotomy to escape predators and there is no regeneration of the missing leg. Here, we tested whether juvenile experience affects adult morph using leg autotomy scars as a proxy of predator encounters. Juvenile males that lost at least one leg (with either locomotory or sensory function) had a 45 times higher probability of becoming a minor morph at adulthood than intact juvenile males. Leg loss during development may affect foraging, locomotion, and/or physiology, potentially linking a juvenile's predator encounters to their final adult morph and future reproductive tactic.
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Affiliation(s)
- Erin C Powell
- Te Kura Mātauranga Koiora/School of Biological Sciences, University of Auckland, 3a Symonds St, Auckland 1010, New Zealand
| | - Christina J Painting
- Te Aka Mātuatua School of Science, University of Waikato, Gate 8, Hillcrest Road, Hamilton 3240, New Zealand
| | - Glauco Machado
- LAGE do Departamento de Ecologia, Instituto de Biociências, Universidade de São Paulo, Rua do Matão, Travessa 14, no. 101, Cidade Universitária, São Paulo CEP 05.508-090, Brazil
| | - Gregory I Holwell
- Te Kura Mātauranga Koiora/School of Biological Sciences, University of Auckland, 3a Symonds St, Auckland 1010, New Zealand
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Miller CH, Haxhillari K, Hillock MF, Reichard TM, Sheehan MJ. Scent mark signal investment predicts fight dynamics in house mice. Proc Biol Sci 2023; 290:20222489. [PMID: 36787797 PMCID: PMC9928526 DOI: 10.1098/rspb.2022.2489] [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: 12/13/2022] [Accepted: 01/23/2023] [Indexed: 02/16/2023] Open
Abstract
Signals mediate competitive interactions by allowing rival assessment, yet are often energetically expensive to produce. One of the key mechanisms maintaining signal reliability is social costs. While the social costs of over-signalling are well known, the social costs of under-signalling are underexplored, particularly for dynamic signals. In this study, we investigate a dynamic and olfactory-mediated signalling system that is ubiquitous among mammals: scent marking. Male house mice territorially scent mark their environment with metabolically costly urine marks. Competitive male mice are thought to deposit abundant scent marks in the environment. However, we recently identified a cohort of low-marking males that win fights. We hypothesized that there may be social costs imposed on individuals who under-invest in signalling. Here we find that scent mark investment predicts fight dynamics. Winning males that produce fewer scent marks prior to a fight engage in more intense fights that take longer to resolve. This effect appears to be driven by an unwillingness among losers to acquiesce to weakly signalling winners. We, therefore, find evidence for rival assessment of scent marks as well as social costs to under-signalling. This supports existing hypotheses for the importance of social punishment in maintaining optimal signalling equilibria. Our results further highlight the possibility of diverse signalling strategies in house mice.
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Affiliation(s)
- Caitlin H. Miller
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA
| | - Klaudio Haxhillari
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA
| | - Matthew F. Hillock
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA
| | - Tess M. Reichard
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA
| | - Michael J. Sheehan
- Department of Neurobiology and Behavior, Cornell University, Ithaca, NY 14853, USA
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7
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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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8
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Sex-specific morphs: the genetics and evolution of intra-sexual variation. Nat Rev Genet 2023; 24:44-52. [PMID: 35971002 DOI: 10.1038/s41576-022-00524-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/19/2022] [Indexed: 11/08/2022]
Abstract
Sex-specific morphs exhibit discrete phenotypes, often including many disparate traits, that are observed in only one sex. These morphs have evolved independently in many different animals and are often associated with alternative mating strategies. The remarkable diversity of sex-specific morphs offers unique opportunities to understand the genetic basis of complex phenotypes, as the distinct nature of many morphs makes it easier to both categorize and compare genomes than for continuous traits. Sex-specific morphs also expand the study of sexual dimorphism beyond traditional bimodal comparisons of male and female averages, as they allow for a more expansive range of sexualization. Although ecological and endocrinological studies of sex-specific morphs have been advancing for some time, genomic and transcriptomic studies of morphs are far more recent. These studies reveal not only many different paths to the evolution of sex-specific morphs but also many commonalities, such as the role of sex-determining genes and hormone signalling in morph development, and the mixing of male and female traits within some morphs.
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9
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Colby AE, DeCasien AR, Cooper EB, Higham JP. Greater variability in rhesus macaque ( Macaca mulatta) endocranial volume among males than females. Proc Biol Sci 2022; 289:20220728. [PMID: 36350207 PMCID: PMC9653222 DOI: 10.1098/rspb.2022.0728] [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: 04/14/2022] [Accepted: 10/05/2022] [Indexed: 11/11/2023] Open
Abstract
The greater male variability (GMV) hypothesis proposes that traits are more variable among males than females, and is supported by numerous empirical studies. Interestingly, GMV is also observed for human brain size and internal brain structure, a pattern which may have implications for sex-biased neurological and psychiatric conditions. A better understanding of neuroanatomical variability in non-human primates may illuminate whether certain species are appropriate models for these conditions. Here, we tested for sex differences in the variability of endocranial volume (ECV, a proxy for brain size) in a sample of 542 rhesus macaques (Macaca mulatta) from a large pedigreed free-ranging population. We also examined the components of phenotypic variance (additive genetic and residual variance) to tease apart the potential drivers of sex differences in variability. Our results suggest that males exhibit more variable ECVs, and that this pattern reflects either balancing/disruptive selection on male behaviour (associated with alternative male mating strategies) or sex chromosome effects (associated with mosaic patterns of X chromosome gene expression in females), rather than extended neurodevelopment among males. This represents evidence of GMV for brain size in a non-human primate species and highlights the potential of rhesus macaques as a model for sex-biased brain-based disorders.
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Affiliation(s)
- Abigail E. Colby
- Department of Anthropology, New York University, New York, NY, USA
- Department of Anthropology and Archaeology, University of Calgary, Calgary, AB, Canada
| | - Alex R. DeCasien
- Department of Anthropology, New York University, New York, NY, USA
- New York Consortium in Evolutionary Primatology, New York, NY, USA
- Section on Developmental Neurogenomics, National Institutes of Health, Bethesda, MD, USA
| | - Eve B. Cooper
- Department of Anthropology, New York University, New York, NY, USA
- New York Consortium in Evolutionary Primatology, New York, NY, USA
| | - 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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10
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Toh KX, Yap S, Goh TG, Puniamoorthy N. Sexual size dimorphism and male reproductive traits vary across populations of a tropical rainforest dung beetle species ( Onthophagus babirussa). Ecol Evol 2022; 12:e9279. [PMID: 36177114 PMCID: PMC9481888 DOI: 10.1002/ece3.9279] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 05/13/2022] [Accepted: 05/16/2022] [Indexed: 11/12/2022] Open
Abstract
Sexual size dimorphism (SSD) arises when natural selection and sexual selection act differently on males and females. Male-biased SSD is rarer in insects and usually indicates strong sexual selection pressure on male body size in a species. Patterns of SSD can also vary between populations of species that are exposed to different environmental conditions, such as differing resource availability and diversity. Here, we investigate intraspecific variation in SSD as well as relative investment in precopulatory (horn length) and postcopulatory traits (sperm length and testes weight) in a tropical rainforest dung beetle Onthophagus babirussa across Singapore and Peninsular Malaysia. Overall, three out of four populations displayed significant male-biased SSD, and SSD was greater in populations with smaller overall body size. Average male body size was similar across all populations while female body size was significantly smaller in Singapore, suggesting that the pronounced SSD may also be due to stronger sexual selection on male body size in Singapore populations. All populations showed significant investment in horns as a weapon likely used in male-male competition, while postcopulatory traits showed no clear scaling relationship with body size, suggesting a higher priority on precopulatory sexual traits in the mating system of this species.
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Affiliation(s)
- Kai Xin Toh
- Department of Biological SciencesNational University of SingaporeSingaporeSingapore
| | - Sean Yap
- Department of Biological SciencesNational University of SingaporeSingaporeSingapore
| | - Thary Gazi Goh
- Institute of Biological Sciences, Science FacultyUniversity of MalayaKuala LumpurMalaysia
| | - Nalini Puniamoorthy
- Department of Biological SciencesNational University of SingaporeSingaporeSingapore
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11
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Is there a trade-off between sperm production and sexual weaponry in the Amazon River prawn Macrobrachium amazonicum (Heller, 1862)? ZOOLOGY 2022; 153:126029. [PMID: 35841878 DOI: 10.1016/j.zool.2022.126029] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Revised: 06/19/2022] [Accepted: 07/01/2022] [Indexed: 11/21/2022]
Abstract
The Amazon River prawn Macrobrachium amazonicum shows populations with four well-defined morphotypes in males. Dominant males of morphotypes green claw 1 (GC1) and green claw 2 (GC2) have large bodies and chelipeds and a higher reproductive success in comparison with the submissive morphotypes - translucent claw (TC) and cinnamon claw (CC). However, recently, some populations of the species do not have dominant morphotypes. Here, we compared the patterns of spermatic production and concentration among morphotypes and populations with three different phenotypes: (i) large-size amphidromous prawns, and (ii) large-size ("i" and "ii" with dominant morphotypes) and (iii) small-size hololimnetic prawns (without morphotypes). We described the spermatogenesis and the histochemical features of vasa deferentia (VD) and evaluated the relationship between the investment in spermatic production and sexual weapons acquisition in males of different phenotypes. The spermatic production and concentration in populations with four morphotypes were similar between morphotypes. The exception was the CC morphotype in which males had the seminiferous tubules filled with spermatocytes and low spermatic concentration. The spermatogenesis, spermiogenesis, and VD structure were not different among the studied phenotypes and populations. The seminal fluid of M. amazonicum is comprised by glycoproteins and by concentric layers of secretions of types I, II (basophilic), and III (eosinophilic). We could infer that males of dominant morphotypes allocate a higher amount of energy to the development of strong sexual weapons at the expense of the energy allocated to the reproductive system during the sequential growth. Inversely, small-size males direct more energy toward the spermatic production and transference at the expense of sexual weapons. Therefore, there is a clear trade-off between the investment in the gonadal and sexual weapons development in males of M. amazonicum.
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12
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Chechi TS, Narasimhan A, Biswas B, Prasad NG. Male mating success evolves in response to increased levels of male-male competition. Evolution 2022; 76:1638-1651. [PMID: 35598115 DOI: 10.1111/evo.14501] [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: 04/08/2021] [Revised: 02/25/2022] [Accepted: 03/04/2022] [Indexed: 01/22/2023]
Abstract
Male-biased operational sex ratios can increase male-male competition and can potentially select for both increased pre- and postcopulatory male success. In the present study, using populations of Drosophila melanogaster evolved under male-biased (M) or female-biased (F) sex ratios, we asked whether (a) male mating success can evolve, (b) males are better at mating females that they have coevolved with, (c) males mating success is affected by female mating status, and (d) male mating success is correlated with their courtship effort. We directly competed M and F males for mating with (a) virgin ancestral (common) females, (b) virgin females from the M and F populations, and (c) singly mated females from the M and F populations. We also assessed the courtship frequency of the males when paired with mated M or F females. Our results show that M males, evolving under an increased level of male-male competition, have higher mating success than F males irrespective of the female evolutionary history. However, the difference in mating success is more pronounced if the females had mated before. M males also have a higher courtship frequency than F males, but we did not find any correlation between mating success and courtship frequency.
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Affiliation(s)
- Tejinder Singh Chechi
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, 140306, India
| | - Aaditya Narasimhan
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, 140306, India
| | - Broti Biswas
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, 140306, India
| | - Nagaraj Guru Prasad
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, 140306, India
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13
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Laini A, Roggero A, Palestrini C, Rolando A. Continuous phenotypic modulation explains male horn allometry in three dung beetle species. Sci Rep 2022; 12:8691. [PMID: 35610305 PMCID: PMC9130230 DOI: 10.1038/s41598-022-12854-6] [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: 09/28/2021] [Accepted: 05/17/2022] [Indexed: 11/09/2022] Open
Abstract
Many dung beetle species show male horn polyphenism, the ability of males to develop into distinct phenotypes without intermediate forms as a response to the larval growth environment. While males with long (majors) and rudimentary (minor) horn have been widely reported in literature, little is known about the existence of individuals with intermediate horn length. Here we investigate the occurrence of intermediates in natural populations of three dung beetle species (Onthophagus furcatus, Copris lunaris and C. hispanus). We analysed the body size-horn length relationship using linear, exponential, and sigmoidal models with different error structures. We inferred the number of individuals in the minor, intermediate, and major groups by combining changepoint analysis and simulation from fitted allometric models. The sigmoidal equation was a better descriptor of the body size-horn length relationship than linear or exponential equations in all the three studied species. Our results indicated that the number of intermediates equals or exceeds the number of minor and major males. This work provides evidence that, at least in the studied species, males with intermediate horn length exist in natural populations. For similar cases we therefore suggest that continuous phenotypic modulation rather than discrete polyphenism can explain variation in male horn allometry.
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Affiliation(s)
- Alex Laini
- Department of Life Sciences and Systems Biology, University of Turin, Via Accademia Albertina 13, 10123, Turin, Italy
| | - Angela Roggero
- Department of Life Sciences and Systems Biology, University of Turin, Via Accademia Albertina 13, 10123, Turin, Italy.
| | - Claudia Palestrini
- Department of Life Sciences and Systems Biology, University of Turin, Via Accademia Albertina 13, 10123, Turin, Italy
| | - Antonio Rolando
- Department of Life Sciences and Systems Biology, University of Turin, Via Accademia Albertina 13, 10123, Turin, Italy
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14
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Freiler MK, Proffitt MR, Smith GT. Electrocommunication signals and aggressive behavior vary among male morphs in an apteronotid fish, Compsaraia samueli. J Exp Biol 2022; 225:275495. [DOI: 10.1242/jeb.243452] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 05/17/2022] [Indexed: 11/20/2022]
Abstract
Within-species variation in male morphology is common among vertebrates and is often characterized by dramatic differences in behavior and hormonal profiles. Males with divergent morphs also often use communication signals in a status-dependent way. Weakly electric knifefish are an excellent system for studying variation in male morphology and communication and its hormonal control. Knifefish transiently modulate the frequency of their electric organ discharge (EOD) during social encounters to produce chirps and rises. In the knifefish Compsaraia samueli, males vary extensively in jaw length. EODs and their modulations (chirps and rises) have never been investigated in this species, so it is unclear whether jaw length is related to the function of these signals. We used three behavioral assays to analyze EOD modulations in male C. samueli: (1) artificial playbacks, (2) relatively brief, live agonistic dyadic encounters, and (3) long-term overnight recordings. We also measured circulating levels of two androgens, 11-ketotestosterone and testosterone. Chirp structure varied within and across individuals in response to artificial playback, but was unrelated to jaw length. Males with longer jaws were more often dominant in dyadic interactions. Chirps and rises were correlated with and preceded attacks regardless of status, suggesting these signals function in aggression. In longer-term interactions, chirp rate declined after one week of pairing, but was unrelated to male morphology. Levels of circulating androgens were low and not predictive of jaw length or EOD signal parameters. These results suggest that communication signals and variation in male morphology are linked to outcomes of non-breeding agonistic contests.
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Affiliation(s)
- Megan K. Freiler
- Department of Biology, Indiana University, 1001 E. 3rd St., Bloomington, IN, 47405, USA
- Center for the Integrative Study of Animal Behavior, Indiana University, 409 N. Park Ave., Bloomington, IN, 47405, USA
| | - Melissa R. Proffitt
- Department of Biology, Indiana University, 1001 E. 3rd St., Bloomington, IN, 47405, USA
- Center for the Integrative Study of Animal Behavior, Indiana University, 409 N. Park Ave., Bloomington, IN, 47405, USA
| | - G. Troy Smith
- Department of Biology, Indiana University, 1001 E. 3rd St., Bloomington, IN, 47405, USA
- Center for the Integrative Study of Animal Behavior, Indiana University, 409 N. Park Ave., Bloomington, IN, 47405, USA
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15
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Williamson NG, Walsh CM, Kijimoto T. Comparative metabolomic analysis of polyphenic horn development in the dung beetle Onthophagus taurus. PLoS One 2022; 17:e0265222. [PMID: 35298496 PMCID: PMC8929603 DOI: 10.1371/journal.pone.0265222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Accepted: 02/25/2022] [Indexed: 11/19/2022] Open
Abstract
Organisms alter their phenotypes in response to changing environmental conditions. The developmental basis of this phenomenon, phenotypic plasticity, is a topic of broad interest in many fields of biology. While insects provide a suitable model for studying the genetic basis of phenotypic plasticity, the physiological aspects of plasticity are not fully understood. Here, we report the physiological basis of polyphenism, an extreme form of phenotypic plasticity by utilizing a dung beetle species, Onthophagus taurus. We highlighted the metabolome between sexes as well as two distinct male morphs—large and small horns. Unlike results from previous transcriptomic studies, the comparative metabolomic study revealed that differences in metabolite level were more prominent between animals with different body sizes than different sexes. Our results also indicate that specific metabolites and biochemical pathways may be active during horn size determination.
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Affiliation(s)
- Naomi G. Williamson
- Division of Plant and Soil Sciences, West Virginia University, Morgantown, West Virginia, United States of America
| | - Callee M. Walsh
- Shared Research Facilities, West Virginia University, Morgantown, West Virginia, United States of America
| | - Teiya Kijimoto
- Division of Plant and Soil Sciences, West Virginia University, Morgantown, West Virginia, United States of America
- * E-mail:
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16
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Dinh JP. Large and exaggerated sexually selected weapons comprise high proportions of metabolically inexpensive exoskeleton. Biol Lett 2022; 18:20210550. [PMID: 35135317 PMCID: PMC8826129 DOI: 10.1098/rsbl.2021.0550] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The cost-minimization hypothesis proposes that positive allometry in sexually selected traits can be explained if the proportional energetic maintenance costs of weapons decrease as traits increase in size. Energetic maintenance costs are the costs of maintaining homeostasis. They are slow, persistent energy sinks that are distinct from ephemeral costs of growth. Because some tissues expend more energy on maintenance than others, energetic maintenance costs can be inferred from proportional tissue composition. For example, soft tissues require more energy for maintenance than exoskeleton, so an arthropod claw that is 50% soft tissue and 50% exoskeleton would have higher energetic maintenance costs than one that is 30% soft tissue and 70% exoskeleton. I tested the cost-minimization hypothesis using proportional tissue composition as a proxy for energetic maintenance costs in snapping shrimp (Alpheus heterochaelis and Alpheus estuariensis) and fiddler crabs (Uca pugilator). As predicted, larger weapons comprised proportionally less soft tissue mass and more exoskeleton mass than smaller weapons. Furthermore, I extended cost-minimization to explain trait exaggeration: individuals might exaggerate traits by investing more mass in exoskeleton. As predicted, exoskeleton mass proportional to weapon mass increased as exaggeration increased. These results support and extend the cost-minimization hypothesis to explain positive allometry and weapon exaggeration.
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Affiliation(s)
- Jason P. Dinh
- Department of Biology, Duke University, Durham, NC, USA
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17
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Leavell BC, Beaty LE, McNickle GG, Bernal XE. Eavesdropping micropredators as dynamic limiters of sexual signal elaboration and intrasexual competition. Am Nat 2022; 199:653-665. [DOI: 10.1086/718967] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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18
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19
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Kienle SS, Friedlaender AS, Crocker DE, Mehta RS, Costa DP. Trade-offs between foraging reward and mortality risk drive sex-specific foraging strategies in sexually dimorphic northern elephant seals. ROYAL SOCIETY OPEN SCIENCE 2022; 9:210522. [PMID: 35116140 PMCID: PMC8767210 DOI: 10.1098/rsos.210522] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 12/14/2021] [Indexed: 05/04/2023]
Abstract
Sex-specific phenotypic differences are widespread throughout the animal kingdom. Reproductive advantages provided by trait differences come at a cost. Here, we link sex-specific foraging strategies to trade-offs between foraging reward and mortality risk in sexually dimorphic northern elephant seals (Mirounga angustirostris). We analyse a decadal dataset on movement patterns, dive behaviour, foraging success and mortality rates. Females are deep-diving predators in open ocean habitats. Males are shallow-diving benthic predators in continental shelf habitats. Males gain six times more mass and acquire energy 4.1 times faster than females. High foraging success comes with a high mortality rate. Males are six times more likely to die than females. These foraging strategies and trade-offs are related to different energy demands and life-history strategies. Males use a foraging strategy with a high mortality risk to attain large body sizes necessary to compete for females, as only a fraction of the largest males ever mate. Females use a foraging strategy with a lower mortality risk, maximizing reproductive success by pupping annually over a long lifespan. Our results highlight how sex-specific traits can drive disparity in mortality rates and expand species' niche space. Further, trade-offs between foraging rewards and mortality risk can differentially affect each sex's ability to maximize fitness.
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Affiliation(s)
- Sarah S. Kienle
- Ecology and Evolutionary Biology, University of California, 130 McAllister Way, Santa Cruz, CA 95060, USA
- Department of Biology, Baylor University, One Bear Place #97399, Waco, TX 76798, USA
| | - Ari S. Friedlaender
- Ocean Science, University of California, 130 McAllister Way, Santa Cruz, CA 95060, USA
| | - Daniel E. Crocker
- Biology, Sonoma State University, 1801 East Cotati Avenue, Rohnert Park, CA 94928, USA
| | - Rita S. Mehta
- Ecology and Evolutionary Biology, University of California, 130 McAllister Way, Santa Cruz, CA 95060, USA
| | - Daniel P. Costa
- Ecology and Evolutionary Biology, University of California, 130 McAllister Way, Santa Cruz, CA 95060, USA
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20
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Xu M, Fincke OM. Negative body size-dependent resource allocation underlies conspicuous sexual ornaments in a territorial damselfly. J Evol Biol 2021; 35:288-298. [PMID: 34825431 DOI: 10.1111/jeb.13963] [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: 06/19/2021] [Revised: 11/10/2021] [Accepted: 11/15/2021] [Indexed: 11/30/2022]
Abstract
Sexual ornaments, signalling individual quality to choosy females or rival males, often show steeper body size scaling compared with non-sexually selected traits. Theory posits such steeper body size scaling is the result of differential resource allocation, reflecting trade-offs between different components of fitness. Yet, the process of resource allocation towards body size-dependent sexual ornaments has been rarely understood empirically. Using the Neotropical territorial damselfly Megaloprepus caerulatus, whose males and females carry wax-based, sex-specific white wing bands and white wing tips respectively, we investigated nutrition sensitivity and body size scaling of both traits by manipulating larval food availability and directly quantified both the fat allocated to wing ornaments and the fat reserve from which allocations are made. Both colour traits exhibited sensitivity to food availability during larval development and steeper body size scaling compared with control traits. Although the absolute amount of fat invested in developing the colour ornaments increased with body size, the proportion of total fat allocated to the ornaments decreased with body size, making exaggerated ornaments less affordable for smaller individuals. Our data demonstrate that measuring the proportion of resource pool from which an individual's ornaments are derived (i.e. its affordability) is essential for understanding the maintenance of honesty of sexual signals.
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Affiliation(s)
- Mingzi Xu
- Ecology and Evolutionary Biology Program, Department of Biology, University of Oklahoma, Norman, Oklahoma, USA.,Department of Ecology, Evolution and Behavior, University of Minnesota, St Paul, Minnesota, USA
| | - Ola M Fincke
- Ecology and Evolutionary Biology Program, Department of Biology, University of Oklahoma, Norman, Oklahoma, USA
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21
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Parrett JM, Slade EM, Knell RJ. Morph‐specific investment in testes mass in a trimorphic beetle,
Proagoderus watanabei. J Zool (1987) 2021. [DOI: 10.1111/jzo.12941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- J. M. Parrett
- Evolutionary Biology Group Faculty of Biology Adam Mickiewicz University Poznań Poland
- School of Biological and Behavioural Sciences Queen Mary, University of London London UK
| | - E. M. Slade
- Asian School of the Environment Nanyang Technological University Singapore City Singapore
| | - R. J. Knell
- School of Biological and Behavioural Sciences Queen Mary, University of London London UK
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22
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Painting CJ. Size and shape variation in the male dimorphic head weapons of an anthribid weevil (Hoherius meinertzhageni). Evol Ecol 2021. [DOI: 10.1007/s10682-021-10127-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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23
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Areja‐Gavina MKD, Torres MC, Gamilla GB, Sakaguchi T, Ito H, Rabajante JF, Tubay JM, Yoshimura J, Morita S. Exaggerated evolution of male armaments via male-male competition. Ecol Evol 2021; 11:6977-6992. [PMID: 34141269 PMCID: PMC8207152 DOI: 10.1002/ece3.7546] [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: 07/20/2020] [Revised: 03/21/2021] [Accepted: 03/22/2021] [Indexed: 11/26/2022] Open
Abstract
Males usually compete to gain access to prospective mates. Through this male-male competition, superior males have a higher chance of passing on their traits to the next generation of male offspring. One category of male traits is armaments, which are weapons used during competition, for example, the chelae of fiddler crabs and the antlers of deer. One consequence of intrasexual selection is the exaggerated evolution of armaments, which can be limited by trade-offs, such as trade-offs with male body size. Here, we formulate a game-theoretic sexual selection model to explore the exaggerated evolution of armaments through male-male competition. The model is used to determine how competition affects the evolution of an armament that is subject to trade-offs. Our simulation can be used to support the exaggerated evolution hypothesis, that is, male-male competition escalates the rate of evolution of armaments.
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Affiliation(s)
- Maica Krizna D. Areja‐Gavina
- Mathematics DivisionInstitute of Mathematical Sciences and PhysicsUniversity of the Philippines Los BañosCollegePhilippines
| | - Monica C. Torres
- Mathematics DivisionInstitute of Mathematical Sciences and PhysicsUniversity of the Philippines Los BañosCollegePhilippines
| | - Gimelle B. Gamilla
- Mathematics DivisionInstitute of Mathematical Sciences and PhysicsUniversity of the Philippines Los BañosCollegePhilippines
| | - Tomohiko Sakaguchi
- Department of Mathematical and Systems EngineeringShizuoka UniversityHamamatsuJapan
| | - Hiromu Ito
- Graduate School of Science and TechnologyShizuoka UniversityHamamatsuJapan
- Department of International HealthInstitute of Tropical MedicineNagasaki UniversityNagasakiJapan
- Department of General Systems StudiesUniversity of TokyoTokyoJapan
| | - Jomar F. Rabajante
- Mathematics DivisionInstitute of Mathematical Sciences and PhysicsUniversity of the Philippines Los BañosCollegePhilippines
- Faculty of EducationUniversity of the Philippines Open UniversityCollege LagunaPhilippines
| | - Jerrold M. Tubay
- Mathematics DivisionInstitute of Mathematical Sciences and PhysicsUniversity of the Philippines Los BañosCollegePhilippines
| | - Jin Yoshimura
- Department of Mathematical and Systems EngineeringShizuoka UniversityHamamatsuJapan
- Graduate School of Science and TechnologyShizuoka UniversityHamamatsuJapan
- Marine Biosystems Research CenterChiba UniversityUchiuraJapan
- Department of Environmental and Forest BiologyState University of New York College of Environmental Science and ForestrySyracuseNYUSA
| | - Satoru Morita
- Department of Mathematical and Systems EngineeringShizuoka UniversityHamamatsuJapan
- Graduate School of Science and TechnologyShizuoka UniversityHamamatsuJapan
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24
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Chung MHJ, Jennions MD, Fox RJ. Quantifying the costs of pre- and postcopulatory traits for males: Evidence that costs of ejaculation are minor relative to mating effort. Evol Lett 2021; 5:315-327. [PMID: 34367658 PMCID: PMC8327938 DOI: 10.1002/evl3.228] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 04/08/2021] [Accepted: 04/12/2021] [Indexed: 12/12/2022] Open
Abstract
Although it is widely stated that both mating behavior and sperm traits are energetically costly for males, we currently lack empirical estimates of the relative costs to males of pre‐ versus postcopulatory investments. Such estimates require the experimental separation of the act of mating from that of ejaculation, which is a nontrivial logistical challenge. Here, we overcome this challenge using a novel morphological manipulation (gonopodium tip ablation) in the eastern mosquitofish (Gambusia holbrooki) to tease apart investment in mating effort from that in sperm replenishment following ejaculation. We quantified the relative cumulative costs of investing in mating effort and ejaculation by comparing somatic traits and reproductive performance among three types of males: ablated males that could attempt to mate but not ejaculate; unablated males that could both mate and ejaculate; and control males that had no access to females. We show that, after eight weeks, mating investment significantly reduces both body growth and immunocompetence and results in a significant decline in mating effort. In contrast, cumulative investment into sperm replenishment following ejaculation has few detectable effects that are only apparent in smaller males. These minor costs occur despite the fact that G. holbrooki has very high levels of sperm competition and multiple mating by both sexes, which is usually associated with elevated levels of sperm production. Crucially, our study is the first, to our knowledge, to experimentally compare the relative costs of pre‐ and postcopulatory investment on components of male fitness in a vertebrate.
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Affiliation(s)
- Meng-Han Joseph Chung
- Division of Ecology and Evolution Research School of Biology Australian National University Canberra ACT 2601 Australia
| | - Michael D Jennions
- Division of Ecology and Evolution Research School of Biology Australian National University Canberra ACT 2601 Australia
| | - Rebecca J Fox
- Division of Ecology and Evolution Research School of Biology Australian National University Canberra ACT 2601 Australia
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25
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Somjee U. Positive allometry of sexually selected traits: Do metabolic maintenance costs play an important role? Bioessays 2021; 43:e2000183. [PMID: 33950569 DOI: 10.1002/bies.202000183] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 03/17/2021] [Accepted: 03/19/2021] [Indexed: 11/07/2022]
Abstract
Sexual selection drives the evolution of some of the most exaggerated traits in nature. Studies on sexual selection often focus on the size of these traits relative to body size, but few focus on energetic maintenance costs of the tissues that compose them, and the ways in which these costs vary with body size. The relationships between energy use and body size have consequences that may allow large individuals to invest disproportionally more in sexually selected structures, or lead to the reduced per-gram maintenance cost of enlarged structures. Although sexually selected traits can incur energetic maintenance costs, these costs are not universally high; they are dependent on the relative mass and metabolic activity of tissues associated with them. Energetic costs of maintenance may play a pervasive yet little-explored role in shaping the relative scaling of sexually selected traits across diverse taxa. Also see the video abstract here: https://youtu.be/JyuoQIeA33Q.
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Affiliation(s)
- Ummat Somjee
- Smithsonian Tropical Research Institute, Panama City, Panama
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26
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Reuland C, Simmons LW, Lüpold S, Fitzpatrick JL. Weapons Evolve Faster Than Sperm in Bovids and Cervids. Cells 2021; 10:cells10051062. [PMID: 33947050 PMCID: PMC8145498 DOI: 10.3390/cells10051062] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 04/25/2021] [Accepted: 04/27/2021] [Indexed: 12/13/2022] Open
Abstract
In polyandrous species, males face reproductive competition both before and after mating. Sexual selection thus shapes the evolution of both pre- and postcopulatory traits, creating competing demands on resource allocation to different reproductive episodes. Traits subject to strong selection exhibit accelerated rates of phenotypic divergence, and examining evolutionary rates may inform us about the relative importance and potential fitness consequences of investing in traits under either pre- or postcopulatory sexual selection. Here, we used a comparative approach to assess evolutionary rates of key competitive traits in two artiodactyl families, bovids (family Bovidae) and cervids (family Cervidae), where male–male competition can occur before and after mating. We quantified and compared evolutionary rates of male weaponry (horns and antlers), body size/mass, testes mass, and sperm morphometrics. We found that weapons evolve faster than sperm dimensions. In contrast, testes and body mass evolve at similar rates. These results suggest strong, but differential, selection on both pre- and postcopulatory traits in bovids and cervids. Furthermore, we documented distinct evolutionary rates among different sperm components, with sperm head and midpiece evolving faster than the flagellum. Finally, we demonstrate that, despite considerable differences in weapon development between bovids and cervids, the overall evolutionary patterns between these families were broadly consistent.
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Affiliation(s)
- Charel Reuland
- Department of Zoology, Stockholm University, Svante Arrhenius väg 18b, 106 91 Stockholm, Sweden;
| | - Leigh W. Simmons
- Centre for Evolutionary Biology, School of Biological Sciences, The University of Western Australia, Crawley, WA 6009, Australia;
| | - Stefan Lüpold
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland;
| | - John L. Fitzpatrick
- Department of Zoology, Stockholm University, Svante Arrhenius väg 18b, 106 91 Stockholm, Sweden;
- Correspondence:
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27
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Cirino LA, Lenga SH, Miller CW. Do males that experience weapon damage have greater reproductive potential than intact males in polygynous scenarios? Behav Ecol Sociobiol 2021. [DOI: 10.1007/s00265-021-03019-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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28
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Liu J, He XZ, Zheng XL, Zhang Y, Wang Q. Larval social cues influence testicular investment in an insect. Curr Zool 2021; 68:1-8. [PMID: 35169624 PMCID: PMC8836345 DOI: 10.1093/cz/zoab028] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Accepted: 03/14/2021] [Indexed: 12/11/2022] Open
Abstract
Socio-sexual environment can have critical impacts on reproduction and survival of animals. Consequently, they need to prepare themselves by allocating more resources to competitive traits that give them advantages in the particular social setting they have been perceiving. Evidence shows that a male usually raises his investment in sperm after he detects the current or future increase of sperm competition because relative sperm numbers can determine his paternity share. This leads to the wide use of testis size as an index of the sperm competition level, yet testis size does not always reflect sperm production. To date, it is not clear whether male animals fine-tune their resource allocation to sperm production and other traits as a response to social cues during their growth and development. Using a polygamous insect Ephestia kuehniella, we tested whether and how larval social environment affected sperm production, testis size, and body weight. We exposed the male larvae to different juvenile socio-sexual cues and measured these traits. We demonstrate that regardless of sex ratio, group-reared males produced more eupyrenes (fertile and nucleate sperm) but smaller testes than singly reared ones, and that body weight and apyrene (infertile and anucleate sperm) numbers remained the same across treatments. We conclude that the presence of larval social, but not sexual cues is responsible for the increase of eupyrene production and decrease of testis size. We suggest that male larvae increase investment in fertile sperm cells and reduce investment in other testicular tissues in the presence of conspecific juvenile cues.
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Affiliation(s)
- Junyan Liu
- School of Agriculture and Environment, Massey University, Palmerston North 4100, New Zealand
| | - Xiong Z He
- School of Agriculture and Environment, Massey University, Palmerston North 4100, New Zealand
| | - Xia-Lin Zheng
- Guangxi Key Laboratory of Agric-Environment and Agric-Products Safety, National Demonstration Centre for Experimental Plant Science Education, College of Agriculture, Guangxi University, Nanning 530004, China
| | - Yujing Zhang
- Guangxi Key Laboratory of Agric-Environment and Agric-Products Safety, National Demonstration Centre for Experimental Plant Science Education, College of Agriculture, Guangxi University, Nanning 530004, China
| | - Qiao Wang
- School of Agriculture and Environment, Massey University, Palmerston North 4100, New Zealand
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29
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Reuland C, Culbert BM, Fernlund Isaksson E, Kahrl AF, Devigili A, Fitzpatrick JL. Male-male behavioral interactions drive social-dominance-mediated differences in ejaculate traits. Behav Ecol 2021; 32:168-177. [PMID: 33708008 PMCID: PMC7937186 DOI: 10.1093/beheco/araa118] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 09/15/2020] [Accepted: 10/08/2020] [Indexed: 12/29/2022] Open
Abstract
Higher social status is expected to result in fitness benefits as it secures access to potential mates. In promiscuous species, male reproductive success is also determined by an individual’s ability to compete for fertilization after mating by producing high-quality ejaculates. However, the complex relationship between a male’s investment in social status and ejaculates remains unclear. Here, we examine how male social status influences ejaculate quality under a range of social contexts in the pygmy halfbeak Dermogenys collettei, a small, group-living, internally fertilizing freshwater fish. We show that male social status influences ejaculate traits, both in the presence and absence of females. Dominant males produced faster swimming and more viable sperm, two key determinants of ejaculate quality, but only under conditions with frequent male–male behavioral interactions. When male–male interactions were experimentally reduced through the addition of a refuge, differences in ejaculate traits of dominant and subordinate males disappeared. Furthermore, dominant males were in a better condition, growing faster, and possessing larger livers, highlighting a possible condition dependence of competitive traits. Contrary to expectations, female presence or absence did not affect sperm swimming speed or testes mass. Together, these results suggest a positive relationship between social status and ejaculate quality in halfbeaks and highlight that the strength of behavioral interactions between males is a key driver of social-status-dependent differences in ejaculate traits.
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Affiliation(s)
- Charel Reuland
- Department of Zoology, Stockholm University, Svante Arrhenius väg 18B, Stockholm, Sweden
| | - Brett M Culbert
- Department of Integrative Biology, University of Guelph, Guelph, Canada
| | | | - Ariel F Kahrl
- Department of Zoology, Stockholm University, Svante Arrhenius väg 18B, Stockholm, Sweden
| | - Alessandro Devigili
- Department of Zoology, Stockholm University, Svante Arrhenius väg 18B, Stockholm, Sweden
| | - John L Fitzpatrick
- Department of Zoology, Stockholm University, Svante Arrhenius väg 18B, Stockholm, Sweden
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30
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Masuoka Y, Nuibe K, Hayase N, Oka T, Maekawa K. Reproductive Soldier Development Is Controlled by Direct Physical Interactions with Reproductive and Soldier Termites. INSECTS 2021; 12:76. [PMID: 33467647 PMCID: PMC7830014 DOI: 10.3390/insects12010076] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 01/13/2021] [Accepted: 01/14/2021] [Indexed: 11/16/2022]
Abstract
In eusocial insects (e.g., ants, bees, and termites), the roles of different castes are assigned to different individuals. These castes possess unique phenotypes that are specialized for specific tasks. The acquisition of sterile individuals with specific roles is considered a requirement for social evolution. In termites, the soldier is a sterile caste. In primitive taxa (family Archotermopsidae and Stolotermitidae), however, secondary reproductives (neotenic reproductives) with their mandibles developed into weapons (so-called reproductive soldiers, also termed as soldier-headed reproductives or soldier neotenics) have been reported. To understand the developmental mechanism of this unique caste, it is necessary to understand the environmental cues and developmental processes of reproductive soldiers under natural conditions. Here, we established efficient conditions to induce reproductive soldiers in Zootermopsis nevadensis. Male reproductive soldiers frequently developed after the removal of both the king and soldiers from an incipient colony. Similarly, high differentiation rates of male reproductive soldiers were observed after king-and-soldier separation treatment using wire mesh. However, no male reproductive soldiers were produced without direct interaction with the queen. These results suggest that male reproductive soldier development is repressed by direct physical interactions with both the king and soldiers and facilitated by direct physical interaction with the queen.
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Affiliation(s)
- Yudai Masuoka
- Institute of Agrobiological Sciences, NARO (National Agriculture and Food Research Organization), Tsukuba 305-8634, Japan;
| | - Keigo Nuibe
- Graduate School of Science and Engineering, University of Toyama, Toyama 930-8555, Japan;
| | - Naoto Hayase
- School of Science, University of Toyama, Toyama 930-8555, Japan; (N.H.); (T.O.)
| | - Takateru Oka
- School of Science, University of Toyama, Toyama 930-8555, Japan; (N.H.); (T.O.)
| | - Kiyoto Maekawa
- Faculty of Science, Academic Assembly, University of Toyama, Toyama 930-8555, Japan
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Matsumura K, Yumise K, Fujii Y, Hayashi T, Miyatake T. Anti-predator behaviour depends on male weapon size. Biol Lett 2020; 16:20200601. [PMID: 33353520 DOI: 10.1098/rsbl.2020.0601] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Tonic immobility and escape are adaptive anti-predator tactics used by many animals. Escape requires movement, whereas tonic immobility does not. If anti-predator tactics relate to weapon size, males with larger weapons may adopt tonic immobility, whereas males with smaller weapons may adopt escape. However, no study has investigated the relationship between weapon size and anti-predator tactics. In this study, we investigated the relationship between male weapon size and tonic immobility in the beetle Gnathocerus cornutus. The results showed that tonic immobility was more frequent in males with larger weapons. Although most studies of tonic immobility in beetles have focused on the duration, rather than the frequency, tonic immobility duration was not affected by weapon size in G. cornutus. Therefore, this study is the first, to our knowledge, to suggest that the male weapon trait affects anti-predator tactics.
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Affiliation(s)
| | - Kota Yumise
- Faculty of Agriculture, Okayama University, Okayama, Japan
| | - Yui Fujii
- Faculty of Agriculture, Okayama University, Okayama, Japan
| | - Toma Hayashi
- Faculty of Agriculture, Okayama University, Okayama, Japan
| | - Takahisa Miyatake
- Graduate School of Environmental and Life Science, Okayama University, Okayama, Japan
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32
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Lai J, Maddison WP, Ma H, Zhang J. Intra‐specific variation of non‐genitalic and genitalic traits in two euophryine jumping spider species. J Zool (1987) 2020. [DOI: 10.1111/jzo.12856] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Affiliation(s)
- J. Lai
- The Key Laboratory of Invertebrate Systematics and Application, College of Life Sciences, Institute of Life Science and Green Development Hebei University Baoding Hebei China
| | - W. P. Maddison
- Departments of Zoology and Botany and Beaty Biodiversity Museum University of British Columbia Vancouver BC Canada
| | - H. Ma
- Hebei Key Laboratory of Wetland Ecology and Conservation Hengshui University Hengshui Hebei China
| | - J. Zhang
- The Key Laboratory of Invertebrate Systematics and Application, College of Life Sciences, Institute of Life Science and Green Development Hebei University Baoding Hebei China
- Hebei Key Laboratory of Wetland Ecology and Conservation Hengshui University Hengshui Hebei China
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33
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Simmons LW, Wedell N. Fifty years of sperm competition: the structure of a scientific revolution. Philos Trans R Soc Lond B Biol Sci 2020; 375:20200060. [PMID: 33070719 DOI: 10.1098/rstb.2020.0060] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Affiliation(s)
- Leigh W Simmons
- Centre for Evolutionary Biology, The University of Western Australia, Crawley 6009, Australia
| | - Nina Wedell
- Centre for Ecology and Conservation, University of Exeter, Cornwall, Penryn TR10 9FE, UK
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34
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35
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Portman SL, Felton GW, Kariyat RR, Marden JH. Host plant defense produces species-specific alterations to flight muscle protein structure and flight-related fitness traits of two armyworms. J Exp Biol 2020; 223:jeb224907. [PMID: 32647018 DOI: 10.1242/jeb.224907] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 06/29/2020] [Indexed: 01/03/2023]
Abstract
Insects manifest phenotypic plasticity in their development and behavior in response to plant defenses, via molecular mechanisms that produce tissue-specific changes. Phenotypic changes might vary between species that differ in their preferred hosts and these effects could extend beyond larval stages. To test this, we manipulated the diet of southern armyworm (SAW; Spodoptera eridania) and fall armyworm (FAW; Spodoptera frugiperda) using a tomato mutant for jasmonic acid plant defense pathway (def1), and wild-type plants, and then quantified gene expression of Troponin t (Tnt) and flight muscle metabolism of the adult insects. Differences in Tnt spliceform ratios in insect flight muscles correlate with changes to flight muscle metabolism and flight muscle output. We found that SAW adults reared on induced def1 plants had a higher relative abundance (RA) of the A isoform of Troponin t (Tnt A) in their flight muscles; in contrast, FAW adults reared on induced def1 plants had a lower RA of Tnt A in their flight muscles compared with adults reared on def1 and controls. Although mass-adjusted flight metabolic rate showed no independent host plant effects in either species, higher flight metabolic rates in SAW correlated with increased RA of Tnt A Flight muscle metabolism also showed an interaction of host plants with Tnt A in both species, suggesting that host plants might be influencing flight muscle metabolic output by altering Tnt This study illustrates how insects respond to variation in host plant chemical defense by phenotypic modifications to their flight muscle proteins, with possible implications for dispersal.
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Affiliation(s)
- Scott L Portman
- Invasive Species and Pollinator Health Research Unit, Western Regional Research Center, United States Department of Agriculture - Agricultural Research Services, 800 Buchanan St, Albany, CA 94710, USA
| | - Gary W Felton
- Department of Entomology, 501 ASI Building, Pennsylvania State University, University Park, PA 16802, USA
| | - Rupesh R Kariyat
- Department of Biology, University of Texas Rio Grande Valley, 1201 W University Drive, Edinburg, TX 78539, USA
- School of Earth, Environment and Marine Sciences, University of Texas Rio Grande Valley, 1201 W University Drive, Edinburg, TX 78539, USA
| | - James H Marden
- Department of Biology, 208 Mueller Laboratory, Pennsylvania State University, University Park, PA 16802, USA
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36
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García-Roa R, Garcia-Gonzalez F, Noble DWA, Carazo P. Temperature as a modulator of sexual selection. Biol Rev Camb Philos Soc 2020; 95:1607-1629. [PMID: 32691483 DOI: 10.1111/brv.12632] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 06/10/2020] [Accepted: 06/12/2020] [Indexed: 12/25/2022]
Abstract
A central question in ecology and evolution is to understand why sexual selection varies so much in strength across taxa; it has long been known that ecological factors are crucial to this. Temperature is a particularly salient abiotic ecological factor that modulates a wide range of physiological, morphological and behavioural traits, impacting individuals and populations at a global taxonomic scale. Furthermore, temperature exhibits substantial temporal variation (e.g. daily, seasonally and inter-seasonally), and hence for most species in the wild sexual selection will regularly unfold in a dynamic thermal environment. Unfortunately, studies have so far almost completely neglected the role of temperature as a modulator of sexual selection. Here, we outline the main pathways through which temperature can affect the intensity and form (i.e. mechanisms) of sexual selection, via: (i) direct effects on secondary sexual traits and preferences (i.e. trait variance, opportunity for selection and trait-fitness covariance), and (ii) indirect effects on key mating parameters, sex-specific reproductive costs/benefits, trade-offs, demography and correlated abiotic factors. Building upon this framework, we show that, by focusing exclusively on the first-order effects that environmental temperature has on traits linked with individual fitness and population viability, current global warming studies may be ignoring eco-evolutionary feedbacks mediated by sexual selection. Finally, we tested the general prediction that temperature modulates sexual selection by conducting a meta-analysis of available studies experimentally manipulating temperature and reporting effects on the variance of male/female reproductive success and/or traits under sexual selection. Our results show a clear association between temperature and sexual selection measures in both sexes. In short, we suggest that studying the feedback between temperature and sexual selection processes may be vital to developing a better understanding of variation in the strength of sexual selection in nature, and its consequences for population viability in response to environmental change (e.g. global warming).
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Affiliation(s)
- Roberto García-Roa
- Behaviour and Evolution, Ethology Lab, Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia, C/Catedrático José Beltrán 2, Paterna, Valencia, 46980, Spain
| | - Francisco Garcia-Gonzalez
- Doñana Biological Station, Spanish Research Council CSIC, c/Americo Vespucio, 26, Isla de la Cartuja, Sevilla, 41092, Spain.,Centre for Evolutionary Biology, School of Biological Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, 6009, Australia
| | - Daniel W A Noble
- Ecology and Evolution Research Centre, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, New South Wales, 2052, Australia.,Division of Ecology and Evolution, Research School of Biology, The Australian National University, Canberra, Australian Capital Territory, 2061, Australia
| | - Pau Carazo
- Behaviour and Evolution, Ethology Lab, Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia, C/Catedrático José Beltrán 2, Paterna, Valencia, 46980, Spain
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37
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Fea MP, Boisseau RP, Emlen DJ, Holwell GI. Cybernetic combatants support the importance of duels in the evolution of extreme weapons. Proc Biol Sci 2020; 287:20200254. [PMID: 32517625 DOI: 10.1098/rspb.2020.0254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
A current evolutionary hypothesis predicts that the most extreme forms of animal weaponry arise in systems where combatants fight each other one-to-one, in duels. It has also been suggested that arms races in human interstate conflicts are more likely to escalate in cases where there are only two opponents. However, directly testing whether duels matter for weapon investment is difficult in animals and impossible in interstate conflicts. Here, we test whether superior combatants experience a disproportionate advantage in duels, as compared with multi-combatant skirmishes, in a system analogous to both animal and military contests: the battles fought by artificial intelligence agents in a computer war game. We found that combatants with experimentally improved fighting power had a large advantage in duels, but that this advantage deteriorated as the complexity of the battlefield was increased by the addition of further combatants. This pattern remained under the two different forms of the advantage granted to our focal artificial intelligence (AI) combatants, and became reversed when we switched the roles to feature a weak focal AI among strong opponents. Our results suggest that one-on-one combat may trigger arms races in diverse systems. These results corroborate the outcomes of studies of both animal and interstate contests, and suggest that elements of animal contest theory may be widely applicable to arms races generally.
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Affiliation(s)
- Murray P Fea
- School of Biological Sciences, The University of Auckland, Auckland, New Zealand
| | - Romain P Boisseau
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA
| | - Douglas J Emlen
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA
| | - Gregory I Holwell
- School of Biological Sciences, The University of Auckland, Auckland, New Zealand
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38
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Mauro AA, Ghalambor CK. Trade-offs, Pleiotropy, and Shared Molecular Pathways: A Unified View of Constraints on Adaptation. Integr Comp Biol 2020; 60:332-347. [DOI: 10.1093/icb/icaa056] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Synopsis
The concept of trade-offs permeates our thinking about adaptive evolution because they are exhibited at every level of biological organization, from molecular and cellular processes to organismal and ecological functions. Trade-offs inevitably arise because different traits do not occur in isolation, but instead are imbedded within complex, integrated systems that make up whole organisms. The genetic and mechanistic underpinning of trade-offs can be found in the pleiotropic nodes that occur in the biological pathways shared between traits. Yet, often trade-offs are only understood as statistical correlations, limiting the ability to evaluate the interplay between how selection and constraint interact during adaptive evolution. Here, we first review the classic paradigms in which physiologists and evolutionary biologists have studied trade-offs and highlight the ways in which network and molecular pathway approaches unify these paradigms. We discuss how these approaches allow researchers to evaluate why trade-offs arise and how selection can act to overcome trait correlations and evolutionary constraints. We argue that understanding how the conserved molecular pathways are shared between different traits and functions provides a conceptual framework for evolutionary biologists, physiologists, and molecular biologists to meaningfully work together toward the goal of understanding why correlations and trade-offs occur between traits. We briefly highlight the melanocortin system and the hormonal control of osmoregulation as two case studies where an understanding of shared molecular pathways reveals why trade-offs occur between seemingly unrelated traits. While we recognize that applying such approaches poses challenges and limitations particularly in the context of natural populations, we advocate for the view that focusing on the biological pathways responsible for trade-offs provides a unified conceptual context accessible to a broad range of integrative biologists.
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Affiliation(s)
- Alexander A Mauro
- Department of Biology and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523, USA
| | - Cameron K Ghalambor
- Department of Biology and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO 80523, USA
- Department of Biology, Centre for Biodiversity Dynamics, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
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39
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Naretto S, Chiaraviglio M. Factors driving sexual dimorphism and colour variability in the Achala Copper Lizard (Pristidactylus achalensis), an endemic species to the highland mountains in central Argentina. CAN J ZOOL 2020. [DOI: 10.1139/cjz-2019-0293] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The intensity of mating competition varies according to the temporal and spatial distribution of individuals. Measuring sexual dimorphism over time and interpreting the association between individuals is therefore important if we aim to understand how sexual traits are influenced. We examined sex differences in the Achala Copper Lizard (Pristidactylus achalensis (Gallardo, 1964)), an endemic species from the highest part of mountains of central Argentina. Over 4 years, we explored sex-specific variation in body size, head size, interlimb length, and body colouration. Furthermore, we evaluated how these traits varied temporally, and we also explored whether the spatial distribution of individuals is explained by variation in these traits. We found that P. achalensis is a species with sexual dimorphism in multiple characters, including body size, head size, and colouration. Interestingly, some traits related to mating, such as head width, show a temporal variability in both sexes, whereas other traits, such as colouration, varies seasonally only in males. Our results underline the intriguing possibility of seasonal morphological changes related to mating, and more broadly that sex differences are influenced by sexual selection pressures mediated by temporal variation in mate competition.
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Affiliation(s)
- S. Naretto
- Laboratorio de Biología del Comportamiento, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Vélez Sársfield 299, CP X5000JJC, Córdoba, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Instituto de Diversidad y Ecología Animal (IDEA), Córdoba, Argentina
- Laboratorio de Biología del Comportamiento, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Vélez Sársfield 299, CP X5000JJC, Córdoba, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Instituto de Diversidad y Ecología Animal (IDEA), Córdoba, Argentina
| | - M. Chiaraviglio
- Laboratorio de Biología del Comportamiento, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Vélez Sársfield 299, CP X5000JJC, Córdoba, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Instituto de Diversidad y Ecología Animal (IDEA), Córdoba, Argentina
- Laboratorio de Biología del Comportamiento, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Vélez Sársfield 299, CP X5000JJC, Córdoba, Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Instituto de Diversidad y Ecología Animal (IDEA), Córdoba, Argentina
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40
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Powell EC, Painting CJ, Hickey AJ, Holwell GI. Defining an intrasexual male weapon polymorphism in a New Zealand harvestman (Opiliones: Neopilionidae) using traditional and geometric morphometrics. Biol J Linn Soc Lond 2020. [DOI: 10.1093/biolinnean/blaa040] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Abstract
In many species, competition for mates has led to exaggerated male sexually-selected traits. Sexually-selected male weapons are used in male-male combat and include structures like horns, antlers and enlarged teeth. Weapons often vary intraspecifically in size, resulting in either a continuum of weapon sizes or in discrete male polymorphisms. More rarely, complex weapon polymorphisms can also include variation in weapon shape; however, these are difficult to quantify. Here we first use traditional linear morphometrics to describe a weapon trimorphism in the endemic New Zealand harvestman, Forsteropsalis pureoraTaylor, 2013. We identified three male morphs: a small-bodied gamma male with reduced chelicera, a large-bodied beta male with long, slender chelicerae, and a large-bodied alpha male with shorter, but very broad, robust chelicerae. Chelicera length alone failed to fully capture the variation in weapon investment. Using geometric morphometrics, we show that alpha males are different in weapon shape, whereas beta and gamma males have similar weapon shape, but vary in their body size and chelicera length. Additionally, we describe how the chelicerae function during male-male combat from observations of contests. This work demonstrates how combining linear and geometric morphometrics can help to elucidate complex polymorphism.
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Affiliation(s)
- Erin C Powell
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Christina J Painting
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
- School of Science, University of Waikato, Hamilton, New Zealand
| | - Anthony J Hickey
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Gregory I Holwell
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
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41
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Allometry and Fighting Behaviour of a Dimorphic Stag Beetle Cyclommatus mniszechi (Coleoptera: Lucanidae). INSECTS 2020; 11:insects11020081. [PMID: 31979391 PMCID: PMC7074643 DOI: 10.3390/insects11020081] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Revised: 01/16/2020] [Accepted: 01/20/2020] [Indexed: 11/30/2022]
Abstract
Male stag beetles (Coleoptera: Lucanidae) use their mandibles as weapons to compete for resources and reproduction. Mandible size in stag beetles can be associated with different behaviours and the outcome of male contests. We investigated the allometric relationship between mandible and body size in males of the stag beetle Cyclommatus mniszechi to uncover distinct morphs. The results divided male C. mniszechi into majors and minors with the switch point of mandible length at 14.01 mm. The allometric slope of mandibles was positive for both morphs but was steeper for the minors. We also characterised the fighting behaviour of the different morphs in size-matched contests using sequential analyses. Males matched each other’s behaviour in contests with many physical contacts, no injury and a progression from low towards high aggression and rare de-escalation. Major and minor males employed the same behavioural elements in contests, but major males were more likely to escalate directly into more aggressive phases and minor males tended to stay within phases. This finding suggests that major males may compete more aggressively than minor males in contests.
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42
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Durrant KL, Reader T, Symonds MRE. Pre- and post-copulatory traits working in concert: sexual dichromatism in passerines is associated with sperm morphology. Biol Lett 2020; 16:20190568. [PMID: 31937213 DOI: 10.1098/rsbl.2019.0568] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Passerine birds produce costly traits under intense sexual selection, including elaborate sexually dichromatic plumage and sperm morphologies, to compete for fertilizations. Plumage and sperm traits vary markedly among species, but it is unknown if this reflects a trade-off between pre- and post-copulatory investment under strong sexual selection producing negative trait covariance, or variation in the strength of sexual selection among species producing positive covariance. Using phylogenetic regression, we analysed datasets describing plumage and sperm morphological traits for 278 passerine species. We found a significant positive relationship between sperm midpiece length and male plumage elaboration and sexual dichromatism. We did not find a relationship between plumage elaboration and testes mass. Our results do not support a trade-off between plumage and sperm traits, but may be indicative of variance among species in the strength of sexual selection to produce both brightly coloured plumage and costly sperm traits.
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Affiliation(s)
- Kate L Durrant
- School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Tom Reader
- School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
| | - Matthew R E Symonds
- Centre for Integrative Ecology, School of Life and Environmental Sciences, Deakin University, Burwood, Victoria 3125, Australia
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43
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Greenway EVG, Cirino LA, Wilner D, Somjee U, Anagnostou ME, Hepple RT, Miller CW. Extreme variation in testes size in an insect is linked to recent mating activity. J Evol Biol 2019; 33:142-150. [PMID: 31765505 DOI: 10.1111/jeb.13574] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 11/08/2019] [Accepted: 11/14/2019] [Indexed: 12/23/2022]
Abstract
Ample sperm production is essential for successful male reproduction in many species. The amount of sperm a male can produce is typically constrained by the size of his testes, which can be energetically expensive to grow and maintain. Although the economics of ejaculate allocation has been the focus of much theoretical and empirical literature, relatively little attention has been paid to individual adult variation and plasticity at the source of sperm production, the testes themselves. We experimentally address this issue using the insect Narnia femorata Stål (Hemiptera: Coreidae). We established the metabolic cost of testicular tissue and then quantified variation in individual testes mass in response to multiple mate quality and quantity treatments. We uncovered extreme variation across individuals and considerable short-term effects of mating activity on testes dry mass. Importantly, the observed variation in testes mass was associated with notable fitness consequences; females paired with males with larger testes had greater hatching success. Overall, pairing with a female resulted in a 11% reduction in dry testes mass. Despite this apparent considerable mating investment, we found no evidence of strategic allocation to higher quality females or longer-term changes in testes mass. The dynamic nature of testes mass and its metabolic cost is vital to consider in the context of re-mating rates, polyandry benefits and general mating system dynamics both in this species and more broadly.
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Affiliation(s)
- E V Ginny Greenway
- Entomology and Nematology Department, University of Florida, Gainesville, Florida
| | - Lauren A Cirino
- Entomology and Nematology Department, University of Florida, Gainesville, Florida
| | - Daniela Wilner
- Entomology and Nematology Department, University of Florida, Gainesville, Florida
| | - Ummat Somjee
- Entomology and Nematology Department, University of Florida, Gainesville, Florida.,Smithsonian Tropical Research Institute, Balboa, Ancon, Panama
| | | | - Russell T Hepple
- Department of Physical Therapy, University of Florida, Gainesville, Florida
| | - Christine W Miller
- Entomology and Nematology Department, University of Florida, Gainesville, Florida
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44
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Meniri M, Gohon F, Gning O, Glauser G, Vallat A, Fasel NJ, Helfenstein F. Experimental manipulation of reproductive tactics in Seba's short-tailed bats: consequences on sperm quality and oxidative status. Curr Zool 2019; 65:609-616. [PMID: 31857807 PMCID: PMC6911846 DOI: 10.1093/cz/zoz011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Accepted: 03/14/2019] [Indexed: 12/25/2022] Open
Abstract
To reproduce, males have to fertilize the female's eggs, sometimes in competition with ejaculates of other males. In species where males display alternative reproductive tactics, whereby territorial males secure mating and non-territorial males have to sneak copulations, the latter might be expected to invest relatively more resources towards sperm quality compared with the territorial males. Sperm cells are especially vulnerable to oxidative stress, which reduces male fertility. Therefore, antioxidant resources are expected to modulate sperm quality, and might be allocated differently between reproductive tactics. To test the link between reproductive tactics, redox profile and sperm quality, we experimentally induced changes in the reproductive tactics of 39 captive males Seba's short-tailed bats Carollia perspicillata. We monitored the blood and ejaculate oxidative balance, and the sperm quality before, 7 days and 21 days after the manipulation of reproductive tactic. Although ejaculates' oxidative damage was negatively related to sperm velocity, males exhibited similar blood and ejaculates redox profiles and similar sperm quality, regardless of their reproductive tactic. Possibly, these results arise as a consequence of some constraints having been lifted during the experiment. Our results also suggest that, in Seba's short-tailed bats, the expression of alternative reproductive tactics is not subjected to strong oxidative constraints. Furthermore, our results could reflect an absence of trade-off between pre- and post-copulatory traits in harem males, as they could be selected to invest both in female attraction and sperm quality, as a consequence of their inability to fully monopolize females.
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Affiliation(s)
- Magali Meniri
- Laboratory of Evolutionary Ecophysiology, Institute of Biology, University of Neuchâtel, Switzerland
| | - Florence Gohon
- Laboratory of Evolutionary Ecophysiology, Institute of Biology, University of Neuchâtel, Switzerland
| | - Ophélie Gning
- Laboratory of Evolutionary Ecophysiology, Institute of Biology, University of Neuchâtel, Switzerland
| | - Gaétan Glauser
- Neuchatel Platform of Analytical Chemistry, University of Neuchâtel, Switzerland
| | - Armelle Vallat
- Neuchatel Platform of Analytical Chemistry, University of Neuchâtel, Switzerland
| | | | - Fabrice Helfenstein
- Laboratory of Evolutionary Ecophysiology, Institute of Biology, University of Neuchâtel, Switzerland
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45
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Baker J, Humphries S, Ferguson-Gow H, Meade A, Venditti C. Rapid decreases in relative testes mass among monogamous birds but not in other vertebrates. Ecol Lett 2019; 23:283-292. [PMID: 31755210 PMCID: PMC6973093 DOI: 10.1111/ele.13431] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 07/26/2019] [Accepted: 10/16/2019] [Indexed: 01/14/2023]
Abstract
Larger testes produce more sperm and therefore improve reproductive success in the face of sperm competition. Adaptation to social mating systems with relatively high and low sperm competition are therefore likely to have driven changes in relative testes size in opposing directions. Here, we combine the largest vertebrate testes mass dataset ever collected with phylogenetic approaches for measuring rates of morphological evolution to provide the first quantitative evidence for how relative testes mass has changed over time. We detect explosive radiations of testes mass diversity distributed throughout the vertebrate tree of life: bursts of rapid change have been frequent during vertebrate evolutionary history. In socially monogamous birds, there have been repeated rapid reductions in relative testes mass. We see no such pattern in other monogamous vertebrates; the prevalence of monogamy in birds may have increased opportunities for investment in alternative behaviours and physiologies allowing reduced investment in expensive testes.
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Affiliation(s)
- Joanna Baker
- School of Biological Sciences, University of Reading, Reading, RG6 6BX, UK
| | - Stuart Humphries
- School of Life Sciences, University of Lincoln, Joseph Banks Laboratories, Green Lane, Lincoln, LN6 7DL, UK
| | - Henry Ferguson-Gow
- Department of Genetics, Evolution and Environment, Centre for Biodiversity and Environment Research, University College London, Gower Street, London, WC1E 6BT, UK
| | - Andrew Meade
- School of Biological Sciences, University of Reading, Reading, RG6 6BX, UK
| | - Chris Venditti
- School of Biological Sciences, University of Reading, Reading, RG6 6BX, UK
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46
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Effects of condition and sperm competition risk on sperm allocation and storage in neriid flies. Behav Ecol 2019. [DOI: 10.1093/beheco/arz178] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
AbstractEjaculate traits can be sexually selected and often exhibit heightened condition-dependence. However, the influence of sperm competition risk in tandem with condition-dependent ejaculate allocation strategies is relatively unstudied. Because ejaculates are costly to produce, high-condition males may be expected to invest more in ejaculates when sperm competition risk is greater. We examined the condition-dependence of ejaculate size by manipulating nutrient concentration in the juvenile (larval) diet of the neriid fly Telostylinus angusticollis. Using a fully factorial design we also examined the effects of perceived sperm competition risk (manipulated by allowing males to mate first or second) on the quantity of ejaculate transferred and stored in the three spermathecae of the female reproductive tract. To differentiate male ejaculates, we fed males nontoxic rhodamine fluorophores (which bind to proteins in the body) prior to mating, labeling their sperm red or green. We found that high-condition males initiated mating more quickly and, when mating second, transferred more ejaculate to both of the female’s posterior spermathecae. This suggests that males allocate ejaculates strategically, with high-condition males elevating their ejaculate investment only when facing sperm competition. More broadly, our findings suggest that ejaculate allocation strategies can incorporate variation in both condition and perceived risk of sperm competition.
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Kim SY, Velando A. Attractive male sticklebacks carry more oxidative DNA damage in the soma and germline. J Evol Biol 2019; 33:121-126. [PMID: 31610052 DOI: 10.1111/jeb.13552] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 10/07/2019] [Accepted: 10/10/2019] [Indexed: 12/23/2022]
Abstract
Trade-offs between the expression of sexual signals and the maintenance of somatic and germline tissues are expected when these depend upon the same resources. Despite the importance of sperm DNA integrity, its trade-off with sexual signalling has rarely been explored. We experimentally tested the trade-off between carotenoid-based sexual coloration and oxidative DNA damage in skeletal muscle, testis and sperm by manipulating reproductive schedule (early vs. late onset of breeding) in male three-spined sticklebacks. Oxidative DNA damage was measured as the amount of 8-hydroxy-2-deoxyguanosine in genomic DNA. Irrespective of the experimentally manipulated reproductive schedule, individuals investing more in red coloration showed higher levels of oxidative DNA damage in muscle, testis and sperm during the peak breeding season. Our results show that the expression of red coloration traded off against the level of oxidative DNA damage possibly due to the competing functions of carotenoids as colorants and antioxidants. Thus, female sticklebacks may risk fertility and viability of offspring by choosing redder, more deteriorated partners with decreased sperm DNA integrity. The evolution of sexual signal may be constrained by oxidative DNA damage in the soma and germline.
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Affiliation(s)
- Sin-Yeon Kim
- Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, Vigo, Spain
| | - Alberto Velando
- Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, Vigo, Spain
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Winkler L, Kirch LM, Reinhold K, Ramm SA. Impact of low sperm competition on male reproductive trait allometries in a bush-cricket. BMC Evol Biol 2019; 19:185. [PMID: 31604422 PMCID: PMC6788016 DOI: 10.1186/s12862-019-1514-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Accepted: 09/16/2019] [Indexed: 01/03/2023] Open
Abstract
Background Studying reproductive trait allometries can help to understand optimal male investment strategies under sexual selection. In promiscuous mating systems, studies across several taxa suggest that testes allometry is usually positive, presumably due to strong selection on sperm numbers through intense sperm competition. Here, we investigated testes allometry in a bush-cricket species, Metaplastes ornatus, in which females mate promiscuously, but where sperm removal behaviour by males likely drastically reduces realised sperm competition level. Results As hypothesised, we found evidence for negative testes allometry and hence a fundamentally different male investment strategy compared to species under intense sperm competition. In addition, the mean relative testes size of M. ornatus was small compared to other species of bush-crickets. Surprisingly, the spermatophore gland, a potential alternative trait that males could invest in instead of testes, also did not show positive allometry, but was approximately isometric. We further observed the expected pattern of negative allometry for the male morphological structure responsible for sperm removal in this species, the subgenital plate, supporting the one-size-fits-all hypothesis for intromittent genitalia. Conclusion Our findings suggest that the evolution of sperm removal behaviour in M. ornatus was a key adaptation for avoiding sperm competition, with important consequences for reproductive trait allometries. Nevertheless, they also imply that it does not pay for larger males to invest disproportionately in nuptial gift production in this species.
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Affiliation(s)
- Lennart Winkler
- Department of Evolutionary Biology, Bielefeld University, Morgenbreede 45, 33615, Bielefeld, Germany
| | - Leon M Kirch
- Department of Evolutionary Biology, Bielefeld University, Morgenbreede 45, 33615, Bielefeld, Germany
| | - Klaus Reinhold
- Department of Evolutionary Biology, Bielefeld University, Morgenbreede 45, 33615, Bielefeld, Germany
| | - Steven A Ramm
- Department of Evolutionary Biology, Bielefeld University, Morgenbreede 45, 33615, Bielefeld, Germany.
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Miller CW, Joseph PN, Kilner RM, Emberts Z. A weapons-testes trade-off in males is amplified in female traits. Proc Biol Sci 2019; 286:20190906. [PMID: 31362640 PMCID: PMC6710601 DOI: 10.1098/rspb.2019.0906] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Accepted: 07/11/2019] [Indexed: 12/29/2022] Open
Abstract
Sexually selected weapons are assumed to trade off with traits related to ejaculates, such as testes. However, remarkably little is known about what governs resource allocation and why trade-offs are found in some cases and not others. Often-used models depict competitive allocation occurring within the functional grouping of traits (e.g. reproduction); however, other factors including tissue expense and developmental timing may influence allocation. Experimental comparisons of investment across the sexes have the potential to illuminate allocation rules, because the sexes do not always use traits for the same functions. Here, we capitalize upon a species where females have weapons-testes homologues. We report that a documented trade-off in investment between hind-limb weapons and testes in leaf-footed cactus bugs, Narnia femorata, is even more pronounced in female hind limbs and ovaries. Female hind limbs in this species do not share the clear reproductive function of male hind limbs; therefore, this trade-off spans trait functional groups. Such patterns of investment suggest that future studies of reproductive trade-offs should consider factors such as tissue expense and developmental timing.
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Affiliation(s)
- Christine W. Miller
- Entomology and Nematology Department, University of Florida, 1881 Natural Area Drive, Gainesville, FL 32611, USA
| | - Paul N. Joseph
- Entomology and Nematology Department, University of Florida, 1881 Natural Area Drive, Gainesville, FL 32611, USA
| | - Rebecca M. Kilner
- Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK
| | - Zachary Emberts
- Department of Biology, University of Florida, 876 Newell Drive, Gainesville, FL 32611, USA
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O'Brien DM, Boisseau RP, Duell M, McCullough E, Powell EC, Somjee U, Solie S, Hickey AJ, Holwell GI, Painting CJ, Emlen DJ. Muscle mass drives cost in sexually selected arthropod weapons. Proc Biol Sci 2019; 286:20191063. [PMID: 31238851 PMCID: PMC6599981 DOI: 10.1098/rspb.2019.1063] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 06/06/2019] [Indexed: 12/11/2022] Open
Abstract
Sexually selected weapons often function as honest signals of fighting ability. If poor-quality individuals produce high-quality weapons, then receivers should focus on other, more reliable signals. Cost is one way to maintain signal integrity. The costs of weapons tend to increase with relative weapon size, and thereby restrict large weapons to high-quality individuals who can produce and maintain them. Weapon cost, however, appears to be unpredictably variable both within and across taxa, and the mechanisms underlying this variation remain unclear. We suggest variation in weapon cost may result from variation in weapon composition-specifically, differences in the amount of muscle mass directly associated with the weapon. We test this idea by measuring the metabolic cost of sexually selected weapons in seven arthropod species and relating these measures to weapon muscle mass. We show that individuals with relatively large weapon muscles have disproportionately high resting metabolic rates and provide evidence that this trend is driven by weapon muscle mass. Overall, our results suggest that variation in weapon cost can be partially explained by variation in weapon morphology and that the integrity of weapon signals may be maintained by increased metabolic cost in species with relatively high weapon muscle mass.
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Affiliation(s)
- Devin M. O'Brien
- Department of Biological Sciences, Colby College, Waterville, ME, USA
- Division of Biological Sciences, University of Montana, Missoula, MT, USA
| | - Romain P. Boisseau
- Division of Biological Sciences, University of Montana, Missoula, MT, USA
| | - Meghan Duell
- School of Life Sciences, Arizona State University, Tempe, AZ, USA
| | - Erin McCullough
- Department of Biology, Syracuse University, Syracuse, NY, USA
| | - Erin C. Powell
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Ummat Somjee
- Entomology and Nematology Department, University of Florida, Gainesville, FL, USA
- Smithsonian Tropical Research Institute, Balboa, Ancón, Panamá
| | - Sarah Solie
- Division of Biological Sciences, University of Montana, Missoula, MT, USA
- Biology Department, Duke University, Durham, NC, USA
| | - Anthony J. Hickey
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Gregory I. Holwell
- School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | | | - Douglas J. Emlen
- Division of Biological Sciences, University of Montana, Missoula, MT, USA
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