1
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Valencia-Aguilar A, Ringler E, Lüpold S, Guayasamin JM, Prado CPA. Evolutionary trade-offs between testes size and parenting in Neotropical glassfrogs. Proc Biol Sci 2024; 291:20240054. [PMID: 38351799 PMCID: PMC10865008 DOI: 10.1098/rspb.2024.0054] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Accepted: 01/18/2024] [Indexed: 02/16/2024] Open
Abstract
In males, large testes size signifies high sperm production and is commonly linked to heightened sperm competition levels. It may also evolve as a response to an elevated risk of sperm depletion due to multiple mating or large clutch sizes. Conversely, weapons, mate or clutch guarding may allow individuals to monopolize mating events and preclude sperm competition, thereby reducing the selection of large testes. Herein, we examined how paternal care, sexual size dimorphism (SSD), weaponry and female fecundity are linked to testes size in glassfrogs. We found that paternal care was associated with a reduction in relative testes size, suggesting an evolutionary trade-off between testes size and parenting. Although females were slightly larger than males and species with paternal care tended to have larger clutches, there was no significant relationship between SSD, clutch size and relative testes size. These findings suggest that the evolution of testes size in glassfrogs is influenced by sperm competition risk, rather than sperm depletion risk. We infer that clutch guarding precludes the risk of fertilization by other males and consequently diminishes selective pressure for larger testes. Our study highlights the prominent role of paternal care in the evolution of testes size in species with external fertilization.
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Affiliation(s)
- Anyelet Valencia-Aguilar
- Pós-Graduação em Ecologia, Evolução e Biodiversidade, Instituto de Biociências, São Paulo State University (Unesp), Rio Claro, São Paulo 13506-900, Brazil
- Division of Behavioural Ecology, Institute of Ecology and Evolution, University of Bern, 3032 Bern, Switzerland
| | - Eva Ringler
- Division of Behavioural Ecology, Institute of Ecology and Evolution, University of Bern, 3032 Bern, Switzerland
| | - Stefan Lüpold
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, 8057 Zurich, Switzerland
| | - Juan M. Guayasamin
- Instituto Biósfera USFQ, Laboratorio de Biología Evolutiva, Universidad San Francisco de Quito USFQ Cumbayá, Quito, Ecuador
| | - Cynthia P. A. Prado
- Pós-Graduação em Ecologia, Evolução e Biodiversidade, Instituto de Biociências, São Paulo State University (Unesp), Rio Claro, São Paulo 13506-900, Brazil
- Departamento de Morfologia e Fisiologia Animal, FCAV, São Paulo State University (Unesp), Jaboticabal, São Paulo 14884-900, Brazil
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2
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Liao W, Jiang Y, Jin L, Lüpold S. How hibernation in frogs drives brain and reproductive evolution in opposite directions. eLife 2023; 12:RP88236. [PMID: 38085091 PMCID: PMC10715729 DOI: 10.7554/elife.88236] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2023] Open
Abstract
Environmental seasonality can promote the evolution of larger brains through cognitive and behavioral flexibility but can also hamper it when temporary food shortage is buffered by stored energy. Multiple hypotheses linking brain evolution with resource acquisition and allocation have been proposed for warm-blooded organisms, but it remains unclear how these extend to cold-blooded taxa whose metabolism is tightly linked to ambient temperature. Here, we integrated these hypotheses across frogs and toads in the context of varying brumation (hibernation) durations and their environmental correlates. We showed that protracted brumation covaried negatively with brain size but positively with reproductive investment, likely in response to brumation-dependent changes in the socio-ecological context and associated selection on different tissues. Our results provide novel insights into resource allocation strategies and possible constraints in trait diversification, which may have important implications for the adaptability of species under sustained environmental change.
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Affiliation(s)
- Wenbo Liao
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal UniversitySichuanChina
- Key Laboratory of Artificial Propagation and Utilization in Anurans of Nanchong City, China West Normal UniversityNanchongChina
- Institute of Eco-Adaptation in Amphibians and Reptiles, China West Normal UniversityNanchongChina
| | - Ying Jiang
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal UniversitySichuanChina
- Key Laboratory of Artificial Propagation and Utilization in Anurans of Nanchong City, China West Normal UniversityNanchongChina
- Institute of Eco-Adaptation in Amphibians and Reptiles, China West Normal UniversityNanchongChina
| | - Long Jin
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal UniversitySichuanChina
- Key Laboratory of Artificial Propagation and Utilization in Anurans of Nanchong City, China West Normal UniversityNanchongChina
- Institute of Eco-Adaptation in Amphibians and Reptiles, China West Normal UniversityNanchongChina
| | - Stefan Lüpold
- Department of Evolutionary Biology and Environmental Studies, University of ZurichZurichSwitzerland
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3
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Liu J, He XZ, Wang Q. Male larval experience of cues from adult rivals alters lifetime sperm investment patterns in a sperm heteromorphic moth, Ephestia kuehniella. INSECT SCIENCE 2023; 30:1773-1783. [PMID: 37162266 DOI: 10.1111/1744-7917.13204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 03/21/2023] [Accepted: 03/28/2023] [Indexed: 05/11/2023]
Abstract
Male animals may adjust their resource allocations for reproduction and other fitness functions in response to cues from rivals. For instance, adult males increase their investment in sperm for a higher paternity share when they perceive sperm competition risk in their surroundings. In nature, both juveniles and adults may coexist spatially and temporally. Yet, it is not clear how juvenile males of different ages respond to cues from adult rivals and fine-tune their lifetime investment in sperm production and ejaculation in any insect. Here we used the Mediterranean flour moth, Ephestia kuehniella, which produces both fertile eupyrene and infertile apyrene sperm, to explore this question. We demonstrate that the late, but not early, instar larvae are sensitive to adult male cues. As a response, they produce more sperm before emergence and their resultant adults have shorter mating latency and ejaculate more sperm in the first few matings. When the juvenile stage produces more eupyrenes, the adult stops making these sperm, but regardless of the number of apyrenes produced during the juvenile stage, the adult continues to make them. These findings suggest that the number of spermatogonia for eupyrenes may be limited and that for apyrenes may be flexible. Our results show that the insect does not trade off survival, mating frequency, body size, or testis size for sperm production in response to adult males during the larval stage. Knowledge created in the present study offers insight into the stage-dependent sensitivity of juvenile males to cues from adult rivals and subsequent lifetime resource allocations.
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Affiliation(s)
- Junyan Liu
- School of Agriculture and Environment, Massey University, Palmerston North, New Zealand
| | - Xiong Zhao He
- School of Agriculture and Environment, Massey University, Palmerston North, New Zealand
| | - Qiao Wang
- School of Agriculture and Environment, Massey University, Palmerston North, New Zealand
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4
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Degueldre F, Aron S. Sperm competition increases sperm production and quality in Cataglyphis desert ants. Proc Biol Sci 2023; 290:20230216. [PMID: 36987648 PMCID: PMC10050944 DOI: 10.1098/rspb.2023.0216] [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: 01/26/2023] [Accepted: 03/10/2023] [Indexed: 03/30/2023] Open
Abstract
Sperm competition is a pervasive evolutionary force that shapes sperm traits to maximize fertilization success. Indeed, it has been shown to increase sperm production in both vertebrates and invertebrates. However, sperm production is energetically costly, which may result in trade-offs among sperm traits. In eusocial hymenopterans, such as ants, mating dynamics impose unique selective pressures on ejaculate. Males are sperm limited: they enter adulthood with a fixed amount of sperm that will not be renewed. We explored whether sperm competition intensity was associated with sperm quantity and quality (i.e. sperm viability and DNA fragmentation) in nine Cataglyphis desert ants. Our results provide phylogenetically robust evidence that sperm competition is positively correlated with sperm production and sperm viability. However, it was unrelated to sperm DNA integrity, indicating the absence of a trade-off involving this trait. These findings underscore that sperm competition may strongly mould sperm traits and drive reproductive performance in eusocial Hymenoptera.
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Affiliation(s)
- Félicien Degueldre
- Evolutionary Biology and Ecology, Université Libre de Bruxelles, Brussels, Brussels B-1050, Belgium
| | - Serge Aron
- Evolutionary Biology and Ecology, Université Libre de Bruxelles, Brussels, Brussels B-1050, Belgium
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5
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Pretterebner K, Pardo LM, Paschke K, Riveros MP. Influence of mating strategies on seminal material investment in crabs. Sci Rep 2022; 12:18376. [PMID: 36319667 PMCID: PMC9626634 DOI: 10.1038/s41598-022-21116-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Accepted: 09/22/2022] [Indexed: 11/05/2022] Open
Abstract
Reproduction involves high energetic costs which are related to behaviour and gamete production. In females energy allocation to gamete production has been well documented. However, estimations of male investment in seminal material are scarce. The present study aims to assess and compare male investment in four brachyuran species by determining biochemical substrates present in the vasa deferentia to subsequently estimate energetic investment during the reproductive cycle. We identified two groups with contrasting energy investments. Two species, Homalaspis plana and Romaleon setosum, showed high investment due to significant quantities of proteins and lipids. Both species are characterised by large and complex vasa deferentia, and the formation of a remarkably large sperm plug deposited to the female after copulation as a sperm competition avoidance strategy. In contrast, Metacarcinus edwardsii and Taliepus dentatus invested little energy in their smaller-sized and simpler vasa deferentia. Morpho-functional traits may play a key role in determining the investment, which may also be influenced by mechanisms (i.e. mating tactics) to prevent sperm competition and the intensity of polygyny. This study emphasises the high amount of energy males invest in seminal material and highlights the diversity of mating strategies in Brachyura, which are reflected even on the physiological level.
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Affiliation(s)
- Katrin Pretterebner
- Programa de Doctorado en Biología Marina, Facultad de Ciencias, Universidad Austral de Chile, 5090000, Valdivia, Chile.
- Laboratorio Costero de Calfuco, Facultad de Ciencias, Instituto de Ciencias Marinas y Limnológicas, Universidad Austral de Chile, 5090000, Valdivia, Chile.
- Centro de Investigación de Dinámica de Ecosistemas Marinos de Altas Latitudes (IDEAL), 5090000, Valdivia, Chile.
| | - Luis Miguel Pardo
- Laboratorio Costero de Calfuco, Facultad de Ciencias, Instituto de Ciencias Marinas y Limnológicas, Universidad Austral de Chile, 5090000, Valdivia, Chile
- Centro de Investigación de Dinámica de Ecosistemas Marinos de Altas Latitudes (IDEAL), 5090000, Valdivia, Chile
| | - Kurt Paschke
- Centro de Investigación de Dinámica de Ecosistemas Marinos de Altas Latitudes (IDEAL), 5090000, Valdivia, Chile
- Instituto de Acuicultura, Universidad Austral de Chile, 5480000, Puerto Montt, Chile
| | - Marcela Paz Riveros
- Programa de Magister en Didáctica de Las Ciencias Experimentales, Facultad de Ciencias, Pontificia Universidad Católica de Valparaíso, 2340000, Valparaíso, Chile
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6
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Johnson BD, Anderson AP, Small CM, Rose E, Flanagan SP, Hendrickson-Rose C, Jones AG. The evolution of the testis transcriptome in pregnant male pipefishes and seahorses. Evolution 2022; 76:2162-2180. [PMID: 35863060 DOI: 10.1111/evo.14579] [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: 01/10/2022] [Revised: 06/17/2022] [Accepted: 06/22/2022] [Indexed: 01/22/2023]
Abstract
In many animals, sperm competition and sexual conflict are thought to drive the rapid evolution of male-specific genes, especially those expressed in the testes. A potential exception occurs in the male pregnant pipefishes, where females transfer eggs to the males, eliminating testes from participating in these processes. Here, we show that testis-related genes differ dramatically in their rates of molecular evolution and expression patterns in pipefishes and seahorses (Syngnathidae) compared to other fish. Genes involved in testis or sperm function within syngnathids experience weaker selection in comparison to their orthologs in spawning and livebearing fishes. An assessment of gene turnover and expression in the testis transcriptome suggests that syngnathids have lost (or significantly reduced expression of) important classes of genes from their testis transcriptomes compared to other fish. Our results indicate that more than 50 million years of male pregnancy have removed syngnathid testes from the molecular arms race that drives the rapid evolution of male reproductive genes in other taxa.
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Affiliation(s)
| | | | - Clayton M Small
- Institute of Ecology and Evolution, University of Oregon, Eugene, Oregon, 97403
| | - Emily Rose
- Department of Biology, Valdosta State University, Valdosta, Georgia, 31698
| | - Sarah P Flanagan
- School of Biological Sciences, University of Canterbury, Christchurch, 8041, New Zealand
| | | | - Adam G Jones
- Department of Biological Sciences, University of Idaho, Moscow, Idaho, 83844
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7
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Dougherty LR, Skirrow MJA, Jennions MD, Simmons LW. Male alternative reproductive tactics and sperm competition: a meta-analysis. Biol Rev Camb Philos Soc 2022; 97:1365-1388. [PMID: 35229450 PMCID: PMC9541908 DOI: 10.1111/brv.12846] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 02/15/2022] [Accepted: 02/16/2022] [Indexed: 01/16/2023]
Abstract
In many animal species, males may exhibit one of several discrete, alternative ways of obtaining fertilisations, known as alternative reproductive tactics (ARTs). Males exhibiting ARTs typically differ in the extent to which they invest in traits that improve their mating success, or the extent to which they face sperm competition. This has led to the widespread prediction that males exhibiting ARTs associated with a high sperm competition risk, or lower investment into traits that improve their competitiveness before mating, should invest more heavily into traits that improve their competitiveness after mating, such as large ejaculates and high-quality sperm. However, despite many studies investigating this question since the 1990s, evidence for differences in sperm and ejaculate investment between male ARTs is mixed, and there has been no quantitative summary of this field. Following a systematic review of the literature, we performed a meta-analysis examining how testes size, sperm number and sperm traits differ between males exhibiting ARTs that face either a high or low sperm competition risk, or high or low investment in traits that increase mating success. We obtained data from 92 studies and 67 species from across the animal kingdom. Our analyses showed that male fish exhibiting ARTs facing a high sperm competition risk had significantly larger testes (after controlling for body size) than those exhibiting tactics facing a low sperm competition risk. However, this effect appears to be due to the inappropriate use of the gonadosomatic index as a body-size corrected measure of testes investment, which overestimates the difference in testes investment between male tactics in most cases. We found no significant difference in sperm number between males exhibiting different ARTs, regardless of whether sperm were measured from the male sperm stores or following ejaculation. We also found no significant difference in sperm traits between males exhibiting different ARTs, with the exception of sperm adenosine triphosphate (ATP) content in fish. Finally, the difference in post-mating investment between male ARTs was not influenced by the extent to which tactics were flexible, or by the frequency of sneakers in the population. Overall, our results suggest that, despite clear theoretical predictions, there is little evidence that male ARTs differ substantially in investment into sperm and ejaculates across species. The incongruence between theoretical and empirical results could be explained if (i) theoretical models fail to account for differences in overall resource levels between males exhibiting different ARTs or fundamental trade-offs between investment into different ejaculate and sperm traits, and (ii) studies often use sperm or ejaculate traits that do not reflect overall post-mating investment accurately or affect fertilisation success.
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Affiliation(s)
- Liam R Dougherty
- Department of Evolution, Ecology and Behaviour, University of Liverpool, Crown Street, Liverpool, L69 7RB, U.K
| | - Michael J A Skirrow
- Division of Ecology & Evolution, Research School of Biology, The Australian National University, 46 Sullivans Creek Road, Canberra, ACT, 2600, Australia
| | - Michael D Jennions
- Division of Ecology & Evolution, Research School of Biology, The Australian National University, 46 Sullivans Creek Road, Canberra, ACT, 2600, Australia
| | - Leigh W Simmons
- Centre for Evolutionary Biology, School of Biological Sciences, The University of Western Australia, Crawley, WA, 6009, Australia
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8
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Sperm Numbers as a Paternity Guard in a Wild Bird. Cells 2022; 11:cells11020231. [PMID: 35053349 PMCID: PMC8773506 DOI: 10.3390/cells11020231] [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: 12/13/2021] [Revised: 01/08/2022] [Accepted: 01/09/2022] [Indexed: 12/02/2022] Open
Abstract
Sperm competition is thought to impose strong selection on males to produce competitive ejaculates to outcompete rival males under competitive mating conditions. Our understanding of how different sperm traits influence fertilization success, however, remains limited, especially in wild populations. Recent literature highlights the importance of incorporating multiple ejaculate traits and pre-copulatory sexually selected traits in analyses aimed at understanding how selection acts on sperm traits. However, variation in a male’s ability to gain fertilization success may also depend upon a range of social and ecological factors that determine the opportunity for mating events both within and outside of the social pair-bond. Here, we test for an effect of sperm quantity and sperm size on male reproductive success in the red-back fairy-wren (Malurus melanocephalus) while simultaneously accounting for pre-copulatory sexual selection and potential socio-ecological correlates of male mating success. We found that sperm number (i.e., cloacal protuberance volume), but not sperm morphology, was associated with reproductive success in male red-backed fairy-wrens. Most notably, males with large numbers of sperm available for copulation achieved greater within-pair paternity success. Our results suggest that males use large sperm numbers as a defensive strategy to guard within-pair paternity success in a system where there is a high risk of sperm competition and female control of copulation. Finally, our work highlights the importance of accounting for socio-ecological factors that may influence male mating opportunities when examining the role of sperm traits in determining male reproductive success.
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9
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Selection on Sperm Count, but Not on Sperm Morphology or Velocity, in a Wild Population of Anolis Lizards. Cells 2021; 10:cells10092369. [PMID: 34572018 PMCID: PMC8464841 DOI: 10.3390/cells10092369] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 09/04/2021] [Accepted: 09/06/2021] [Indexed: 12/25/2022] Open
Abstract
Sperm competition is a widespread phenomenon that shapes male reproductive success. Ejaculates present many potential targets for postcopulatory selection (e.g., sperm morphology, count, and velocity), which are often highly correlated and potentially subject to complex multivariate selection. Although multivariate selection on ejaculate traits has been observed in laboratory experiments, it is unclear whether selection is similarly complex in wild populations, where individuals mate frequently over longer periods of time. We measured univariate and multivariate selection on sperm morphology, sperm count, and sperm velocity in a wild population of brown anole lizards (Anolis sagrei). We conducted a mark-recapture study with genetic parentage assignment to estimate individual reproductive success. We found significant negative directional selection and negative quadratic selection on sperm count, but we did not detect directional or quadratic selection on any other sperm traits, nor did we detect correlational selection on any trait combinations. Our results may reflect pressure on males to produce many small ejaculates and mate frequently over a six-month reproductive season. This study is the first to measure multivariate selection on sperm traits in a wild population and provides an interesting contrast to experimental studies of external fertilizers, which have found complex multivariate selection on sperm phenotypes.
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10
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Resende FCD, Avelar GFD. The sexual segment of the kidney of a tropical rattlesnake, Crotalus durissus (Reptilia, Squamata, Viperidae), and its relationship to seasonal testicular and androgen cycles. J Morphol 2021; 282:1402-1414. [PMID: 34219274 DOI: 10.1002/jmor.21394] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 06/28/2021] [Accepted: 07/03/2021] [Indexed: 11/10/2022]
Abstract
The sexual segment of the kidney (SSK) is a hypertrophied region of the nephron, which occurs in males of most squamate species that have been investigated, at least, during the active season. Many studies have shown that the SSK has a seasonal secretory cycle that could be correlated to the mating season, testicular activity, and androgen synthesis. However, to date, no study has investigated the presence of androgen receptors (AR) in cells of the SSK, nor the relation between the expression of AR, testosterone levels, and testicular condition. The SSK in Crotalus durissus corresponds to the distal segment of the nephron and presents a peak of hypertrophy during the period of testicular activity (spermatogenesis) and high testosterone levels, suggesting that seasonal variation of the SSK might be under the control of androgens. Testosterone concentrations and expression of AR varied seasonally with increased values for both parameters directly correlated to hypertrophy of the SSK. This study is, therefore, the first to target the SSK of a tropical snake and to establish a relationship between the secretory cycle of the SSK, testicular cycle, and levels of androgens. Furthermore, this study is the first to identify the presence of AR in the nucleus of the SSK cells.
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Affiliation(s)
- Flávia Cappuccio de Resende
- Laboratory of Cellular Biology, Department of Morphology, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.,Scientific Collection of Snakes, Ezequiel Dias Foundation, Belo Horizonte, Minas Gerais, Brazil
| | - Gleide Fernandes de Avelar
- Laboratory of Cellular Biology, Department of Morphology, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
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11
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Lüpold S, de Boer RA, Evans JP, Tomkins JL, Fitzpatrick JL. How sperm competition shapes the evolution of testes and sperm: a meta-analysis. Philos Trans R Soc Lond B Biol Sci 2020; 375:20200064. [PMID: 33070733 DOI: 10.1098/rstb.2020.0064] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Females of many species mate with multiple males, thereby inciting competition among ejaculates from rival males for fertilization. In response to increasing sperm competition, males are predicted to enhance their investment in sperm production. This prediction is so widespread that testes size (correcting for body size) is commonly used as a proxy of sperm competition, even in the absence of any other information about a species' reproductive behaviour. By contrast, a debate about whether sperm competition selects for smaller or larger sperm has persisted for nearly three decades, with empirical studies demonstrating every possible response. Here, we synthesize nearly 40 years of sperm competition research in a meta-analytical framework to determine how the evolution of sperm number (i.e. testes size) and sperm size (i.e. sperm head, midpiece, flagellum and total length) is influenced by varying levels of sperm competition across species. Our findings support the long-held assumption that higher levels of sperm competition are associated with relatively larger testes. We also find clear evidence that sperm competition is associated with increases in all components of sperm length. We discuss these results in the context of different theoretical predictions and general patterns in the breeding biology and selective environment of sperm. This article is part of the theme issue 'Fifty years of sperm competition'.
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Affiliation(s)
- Stefan Lüpold
- Department of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Raïssa A de Boer
- Department of Zoology/Ethology, Stockholm University, Svante Arrhenius väg 18B, Stockholm 10691, Sweden
| | - Jonathan P Evans
- Centre for Evolutionary Biology, School of Biological Sciences (M092), University of Western Australia, Crawley, Western Australia 6009, Australia
| | - Joseph L Tomkins
- Centre for Evolutionary Biology, School of Biological Sciences (M092), University of Western Australia, Crawley, Western Australia 6009, Australia
| | - John L Fitzpatrick
- Department of Zoology/Ethology, Stockholm University, Svante Arrhenius väg 18B, Stockholm 10691, Sweden
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12
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Lemaître JF, Gaillard JM, Ramm SA. The hidden ageing costs of sperm competition. Ecol Lett 2020; 23:1573-1588. [PMID: 32906225 DOI: 10.1111/ele.13593] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 06/30/2020] [Accepted: 07/22/2020] [Indexed: 12/16/2022]
Abstract
Ageing and sexual selection are intimately linked. There is by now compelling evidence from studies performed across diverse organisms that males allocating resources to mating competition incur substantial physiological costs, ultimately increasing ageing. However, although insightful, we argue here that to date these studies cover only part of the relationship linking sexual selection and ageing. Crucially, allocation to traits important in post-copulatory sexual selection, that is sperm competition, has been largely ignored. As we demonstrate, such allocation could potentially explain much diversity in male and female ageing patterns observed both within and among species. We first review how allocation to sperm competition traits such as sperm and seminal fluid production depends on the quality of resources available to males and can be associated with a wide range of deleterious effects affecting both somatic tissues and the germline, and thus modulate ageing in both survival and reproductive terms. We further hypothesise that common biological features such as plasticity, prudent sperm allocation and seasonality of ejaculate traits might have evolved as counter-adaptations to limit the ageing costs of sperm competition. Finally, we discuss the implications of these emerging ageing costs of sperm competition for current research on the evolutionary ecology of ageing.
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Affiliation(s)
- Jean-François Lemaître
- Université de Lyon, Université Lyon 1, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR5558, Villeurbanne, F-69622, France
| | - Jean-Michel Gaillard
- Université de Lyon, Université Lyon 1, CNRS, Laboratoire de Biométrie et Biologie Evolutive UMR5558, Villeurbanne, F-69622, France
| | - Steven A Ramm
- Evolutionary Biology, Bielefeld University, Konsequenz 45, Bielefeld, 33615, Germany
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13
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Murray RL, Herridge EJ, Ness RW, Wiberg RAW, Bussière LF. Competition for access to mates predicts female-specific ornamentation and male investment in relative testis size. Evolution 2020; 74:1741-1754. [PMID: 32352568 DOI: 10.1111/evo.13986] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Revised: 03/26/2020] [Accepted: 04/05/2020] [Indexed: 11/30/2022]
Abstract
Sexually selected ornaments are highly variable and the factors that drive variation in ornament expression are not always clear. Rare instances of female-specific ornament evolution (such as in some dance fly species) are particularly puzzling. While some evidence suggests that such rare instances represent straightforward reversals of sexual selection intensity, the distinct nature of trade-offs between ornaments and offspring pose special constraints in females. To examine whether competition for access to mates generally favors heightened ornament expression, we built a phylogeny and conducted a comparative analysis of Empidinae dance fly taxa that display female-specific ornaments. We show that species with more female-biased operational sex ratios in lek-like mating swarms have greater female ornamentation, and in taxa with more ornate females, male relative testis investment is increased. These findings support the hypothesis that ornament diversity in dance flies depends on female receptivity to mates, which is associated with contests for nutritious nuptial gifts provided by males. Moreover, our results suggest that increases in female receptivity lead to higher levels of sperm competition among males. The incidence of both heightened premating sexual selection on females and postmating selection on males contradicts assertions that sex roles are straightforwardly reversed in dance flies.
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Affiliation(s)
- Rosalind L Murray
- Biology Department, University of Toronto, Mississauga, Ontario, L5L 1C6, Canada.,Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, M5S 3B2, Canada.,Biological and Environmental Sciences, University of Stirling, Stirling, Scotland, FK9 4LA, United Kingdom
| | - Elizabeth J Herridge
- Biological and Environmental Sciences, University of Stirling, Stirling, Scotland, FK9 4LA, United Kingdom
| | - Rob W Ness
- Biology Department, University of Toronto, Mississauga, Ontario, L5L 1C6, Canada.,Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, M5S 3B2, Canada
| | - R Axel W Wiberg
- Department of Environmental Sciences, Evolutionary Biology, University of Basel, Basel, 4051, Switzerland
| | - Luc F Bussière
- Biological and Environmental Sciences, University of Stirling, Stirling, Scotland, FK9 4LA, United Kingdom
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14
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Liao WB, Zhong MJ, Lüpold S. Sperm quality and quantity evolve through different selective processes in the Phasianidae. Sci Rep 2019; 9:19278. [PMID: 31848414 PMCID: PMC6917726 DOI: 10.1038/s41598-019-55822-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2018] [Accepted: 12/03/2019] [Indexed: 11/09/2022] Open
Abstract
Sperm competition is often considered the primary selective force underlying the rapid and diversifying evolution of ejaculate traits. Yet, several recent studies have drawn attention to other forms of selection with the potential of exceeding the effects of sperm competition. Since ejaculates are complex, multivariate traits, it seems plausible that different ejaculate components vary in their responses to different selective pressures. Such information, however, is generally lacking as individual ejaculate traits tend to be studied in isolation. Here, we studied the macroevolutionary patterns of ejaculate volume, sperm number, sperm length and the proportion of viable normal sperm in response to varying levels of sperm competition, body size and the duration of female sperm storage in pheasants and allies (Phasianidae). Ejaculate volume, sperm number and sperm viability were all relatively higher in polygamous than in monogamous mating systems. However, whereas ejaculate volume additionally covaried with body size, sperm number instead increased with the female sperm-storage duration, in conjunction with a decrease in sperm length. Overall, our results revealed important details on how different forms of selection can jointly shape ejaculates as complex, composite traits.
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Affiliation(s)
- Wen Bo Liao
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal University, Nanchong, 637009, Sichuan, China. .,Key Laboratory of Artificial Propagation and Utilization in Anurans of Nanchong City, China West Normal University, Nanchong, Sichuan, 637009, China. .,Institute of Eco-adaptation in Amphibians and Reptiles, China West Normal University, Nanchong, 637009, Sichuan, China.
| | - Mao Jun Zhong
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal University, Nanchong, 637009, Sichuan, China.,Key Laboratory of Artificial Propagation and Utilization in Anurans of Nanchong City, China West Normal University, Nanchong, Sichuan, 637009, China.,Institute of Eco-adaptation in Amphibians and Reptiles, China West Normal University, Nanchong, 637009, Sichuan, China
| | - Stefan Lüpold
- Department of Evolutionary Biology and Environmental Studies, University of Zurich-Irchel, 8057, Zurich, Switzerland
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15
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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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16
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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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17
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Macartney EL, Crean AJ, Nakagawa S, Bonduriansky R. Effects of nutrient limitation on sperm and seminal fluid: a systematic review and meta-analysis. Biol Rev Camb Philos Soc 2019; 94:1722-1739. [PMID: 31215758 DOI: 10.1111/brv.12524] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2019] [Revised: 05/01/2019] [Accepted: 05/03/2019] [Indexed: 01/05/2023]
Abstract
Theory predicts that costly sexual traits should be reduced when individuals are in poor condition (i.e. traits should exhibit condition-dependent expression). It is therefore widely expected that male ejaculate traits, such as sperm and seminal fluid, will exhibit reduced quantity and quality when dietary nutrients are limited. However, reported patterns of ejaculate condition dependence are highly variable, and there has been no comprehensive synthesis of underlying sources of such variation in condition-dependent responses. In particular, it remains unclear whether all ejaculate traits are equally sensitive to nutrient intake, and whether such traits are particularly sensitive to certain dietary nutrients, respond more strongly to nutrients during specific life stages, or respond more strongly in some taxonomic groups. We systematically reviewed these potential sources of variation through a meta-analysis across 50 species of arthropods and vertebrates (from 71 papers and 348 effect sizes). We found that overall, ejaculate traits are moderately reduced when dietary nutrients are limited, but we also detected substantial variation in responses. Seminal fluid quantity was strongly and consistently condition dependent, while sperm quantity was moderately condition dependent. By contrast, aspects of sperm quality (particularly sperm viability and morphology) were less consistently reduced under nutrient limitation. Ejaculate traits tended to respond in a condition-dependent manner to a wide range of dietary manipulations, especially to caloric and protein restriction. Finally, while all major taxa for which sufficient data exist (i.e. arthropods, mammals, fish) showed condition dependence of ejaculate traits, we detected some taxonomic differences in the life stage that is most sensitive to nutrient limitation, and in the degree of condition dependence of specific ejaculate traits. Together, these biologically relevant factors accounted for nearly 20% of the total variance in ejaculate responses to nutrient limitation. Interestingly, body size showed considerably stronger condition-dependent responses compared to ejaculate traits, suggesting that ejaculate trait expression may be strongly canalised to protect important reproductive functions, or that the cost of producing an ejaculate is relatively low. Taken together, our findings show that condition-dependence of ejaculate traits is taxonomically widespread, but there are also many interesting, biologically relevant sources of variation that require further investigation. In particular, further research is needed to understand the differences in selective pressures that result in differential patterns of ejaculate condition dependence across taxa and ejaculate traits.
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Affiliation(s)
- Erin L Macartney
- Evolution and Ecology Research Centre and School of Biological, Earth and Environmental Sciences, UNSW Australia, Sydney, New South Wales, Australia
| | - Angela J Crean
- Sydney School of Veterinary Science, The University of Sydney, Sydney, New South Wales, Australia
| | - Shinichi Nakagawa
- Evolution and Ecology Research Centre and School of Biological, Earth and Environmental Sciences, UNSW Australia, Sydney, New South Wales, Australia
| | - Russell Bonduriansky
- Evolution and Ecology Research Centre and School of Biological, Earth and Environmental Sciences, UNSW Australia, Sydney, New South Wales, Australia
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18
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Rosa ME, Kiss J, Barta Z, Kosztolányi A. Size‐dependent investment in tusk length, testis size and sperm length in a biparental geotrupid beetle. J Zool (1987) 2019. [DOI: 10.1111/jzo.12704] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- M. E. Rosa
- Department of Ecology University of Veterinary Medicine Budapest Budapest Hungary
- Doctoral School of Biological Sciences Szent István University Gödöllő Hungary
| | - J. Kiss
- MTA‐DE Behavioural Ecology Research Group, Department of Evolutionary Zoology and Human Biology University of Debrecen Debrecen Hungary
| | - Z. Barta
- MTA‐DE Behavioural Ecology Research Group, Department of Evolutionary Zoology and Human Biology University of Debrecen Debrecen Hungary
| | - A. Kosztolányi
- Department of Ecology University of Veterinary Medicine Budapest Budapest Hungary
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19
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Dorková M, Naďo L, Jarčuška B, Kaňuch P. Size-dependent mating pattern in a nuptial gift-giving insect. Ecol Evol 2019; 9:454-462. [PMID: 30680127 PMCID: PMC6342177 DOI: 10.1002/ece3.4763] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Revised: 11/09/2018] [Accepted: 11/12/2018] [Indexed: 11/29/2022] Open
Abstract
The reproductive interests of females and males often diverge in terms of the number of mating partners, an individual's phenotype, origin, genes, and parental investment. This conflict may lead to a variety of sex-specific adaptations and also affect mate choice in both sexes. We conducted an experiment with the bush-cricket Pholidoptera griseoaptera (Orthoptera, Tettigoniidae), a species in which females receive direct nutritional benefits during mating. Mated individuals could be assigned due to the genotype of male spermatodoses, which are stored in the female's spermatheca. After 3 weeks of possible copulations in established mating groups which were random replications with four females and males we did not find consistent assortative mating preference regarding to body size of mates. However, our results showed that the frequency of within-pair copulations (192 analyzed mating events in 128 possible pairwise combinations) was positively associated with the body size of both mated individuals with significant interaction between sexes (having one mate very large, association between body size and the number of copulations has weaken). Larger individuals also showed a higher degree of polygamy. This suggests that body size of this nuptial gift-giving insect species is an important sexual trait according to which both sexes choose their optimal mating partner.
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Affiliation(s)
- Martina Dorková
- Institute of Forest EcologySlovak Academy of SciencesZvolenSlovakia
- Faculty of Ecology and Environmental SciencesTechnical University in ZvolenZvolenSlovakia
| | - Ladislav Naďo
- Institute of Forest EcologySlovak Academy of SciencesZvolenSlovakia
| | | | - Peter Kaňuch
- Institute of Forest EcologySlovak Academy of SciencesZvolenSlovakia
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20
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Boulton RA, Zuk M, Shuker DM. An Inconvenient Truth: The Unconsidered Benefits of Convenience Polyandry. Trends Ecol Evol 2018; 33:904-915. [PMID: 30376988 DOI: 10.1016/j.tree.2018.10.002] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2017] [Revised: 09/19/2018] [Accepted: 10/02/2018] [Indexed: 12/22/2022]
Abstract
Polyandry, or multiple mating by females with different males, is commonplace. One explanation is that females engage in convenience polyandry, mating multiple times to reduce the costs of sexual harassment. Although the logic underlying convenience polyandry is clear, and harassment often seems to influence mating outcomes, it has not been subjected to as thorough theoretical or empirical attention as other explanations for polyandry. We re-examine here convenience polyandry in the light of new studies demonstrating previously unconsidered benefits of polyandry. We suggest that true convenience polyandry is likely to be a fleeting phenomenon, even though it can profoundly shape mating-system evolution via potential feedback loops between resistance to males and the costs and benefits of mating.
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Affiliation(s)
- Rebecca A Boulton
- College of Life and Environmental Sciences, University of Exeter, Penryn, Cornwall TR10 9FE, UK; Department of Entomology, University of Minnesota, St Paul, MN 55108, USA; School of Biology, University of St Andrews, St Andrews KY16 9TH, UK.
| | - Marlene Zuk
- Department of Ecology, Evolution and Behavior, University of Minnesota, St Paul, MN 55108, USA
| | - David M Shuker
- School of Biology, University of St Andrews, St Andrews KY16 9TH, UK
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21
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Villagrán M, Beracochea F, Bartoš L, Ungerfeld R. Hierarchical status and body traits and reproductive characteristics of male pampas deer (Ozotoceros bezoarticus) maintained in all-male groups. Appl Anim Behav Sci 2018. [DOI: 10.1016/j.applanim.2018.07.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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22
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Koschmieder M, Müller M, Reinhold K, Ramm SA. Divergent testis allometry in two subspecies of the bushcricket Poecilimon veluchianus. Biol J Linn Soc Lond 2018. [DOI: 10.1093/biolinnean/bly018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Affiliation(s)
- Mark Koschmieder
- Department of Evolutionary Biology, Bielefeld University, Morgenbreede, Bielefeld, Germany
| | - Martin Müller
- Department of Evolutionary Biology, Bielefeld University, Morgenbreede, Bielefeld, Germany
| | - Klaus Reinhold
- Department of Evolutionary Biology, Bielefeld University, Morgenbreede, Bielefeld, Germany
| | - Steven A Ramm
- Department of Evolutionary Biology, Bielefeld University, Morgenbreede, Bielefeld, Germany
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23
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Seaver CMS, Hurd PL. Are there consistent behavioral differences between sexes and male color morphs in Pelvicachromis pulcher? ZOOLOGY 2017; 122:115-125. [PMID: 28546067 DOI: 10.1016/j.zool.2017.05.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2016] [Revised: 05/04/2017] [Accepted: 05/04/2017] [Indexed: 11/18/2022]
Abstract
Adult sex ratios in the kribensis cichlid (Pelvicachromis pulcher) are influenced by environmental conditions during early development. These environmental sex-determining factors may also organize life-long variation in social behavior within each sex. If this is true, then individual differences in behavior may be, at least in part, expressions of the relative strength of sexual differentiation of that individual. As adults, kribensis males take on one of four alternative color morphs. Males of the yellow morph tend toward breeding monogamously and are produced at higher frequency under female-biasing environmental conditions, while males of the red morph tend more towards breeding polygynously and are produced more frequently by male-biasing early environments. Here we test whether these two alternative kribensis male color morphs show consistent behavioral differences as predicted by an underlying behavioral syndrome of relative feminization to masculinization. We compare these males to females in five different behavioral tests: an aggression assay, an open field exploration task, a novel environment emergence task, and three cerebral lateralization tests. We hypothesize that red males will show more exaggerated sex differences across all behaviors. We find that red males are hypermasculinized as predicted with respect to aggressive behavior and activity levels, but not all behaviors follow this pattern. We find no evidence for a common behavioral syndrome underlying personality traits across females, yellow males and red males.
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Affiliation(s)
- Cheryl M Sedlak Seaver
- Department of Psychology, P217 Biological Sciences Building, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
| | - Peter L Hurd
- Department of Psychology, P217 Biological Sciences Building, University of Alberta, Edmonton, Alberta T6G 2E1, Canada; Neuroscience and Mental Health Institute, University of Alberta, 4-120 Katz Group Centre, Edmonton, Alberta T6G 2E1, Canada.
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24
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Lüpold S, Jin L, Liao WB. Population density and structure drive differential investment in pre- and postmating sexual traits in frogs. Evolution 2017; 71:1686-1699. [PMID: 28394412 DOI: 10.1111/evo.13246] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Accepted: 03/25/2017] [Indexed: 01/01/2023]
Abstract
Sexual selection theory predicts a trade-off between premating (ornaments and armaments) and postmating (testes and ejaculates) sexual traits, assuming that growing and maintaining these traits is costly and that total reproductive investments are limited. The number of males in competition, the reproductive gains from investing in premating sexual traits, and the level of sperm competition are all predicted to influence how males allocate their finite resources to these traits. Yet, empirical examination of these predictions is currently scarce. Here, we studied relative expenditure on pre- and postmating sexual traits among frog species varying in their population density, operational sex ratio, and the number of competing males for each clutch of eggs. We found that the intensifying struggle to monopolize fertilizations as more and more males clasp the same female to fertilize her eggs shifts male reproductive investment toward sperm production and away from male weaponry. This shift, which is mediated by population density and the associated level of male-male competition, likely also explains the trade-off between pre- and postmating sexual traits in our much broader sample of anuran species. Our results highlight the power of such a multilevel approach in resolving the evolution of traits and allocation trade-offs.
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Affiliation(s)
- Stefan Lüpold
- Department of Evolutionary Biology and Environmental Studies, University of Zurich-Irchel, Winterthurerstrasse 190, 8057, Zurich, Switzerland
| | - Long Jin
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal University, Nanchong, 637009, P. R. China
| | - Wen Bo Liao
- Key Laboratory of Southwest China Wildlife Resources Conservation (Ministry of Education), China West Normal University, Nanchong, 637009, P. R. China
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25
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McNamara KB, Robinson SP, Rosa ME, Sloan NS, van Lieshout E, Simmons LW. Male-biased sex ratio does not promote increased sperm competitiveness in the seed beetle, Callosobruchus maculatus. Sci Rep 2016; 6:28153. [PMID: 27306351 PMCID: PMC4910101 DOI: 10.1038/srep28153] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 05/27/2016] [Indexed: 11/09/2022] Open
Abstract
Sperm competition risk and intensity can select for adaptations that increase male fertilisation success. Evolutionary responses are examined typically by generating increased strength of sexual selection via direct manipulation of female mating rates (by enforcing monandry or polyandry) or by alteration of adult sex ratios. Despite being a model species for sexual selection research, the effect of sexual selection intensity via adult sex-ratio manipulation on male investment strategies has not been investigated in the seed beetle, Callosobruchus maculatus. We imposed 32 generations of experimental evolution on 10 populations of beetles by manipulating adult sex ratio. Contrary to predictions, males evolving in male-biased populations did not increase their testes and accessory gland size. This absence of divergence in ejaculate investment was also reflected in the fact that males from male-biased populations were not more successful in either preventing females from remating, or in competing directly for fertilisations. These populations already demonstrate divergence in mating behaviour and immunity, suggesting sufficient generations have passed to allow divergence in physiological and behavioural traits. We propose several explanations for the absence of divergence in sperm competitiveness among our populations and the pitfalls of using sex ratio manipulation to assess evolutionary responses to sexual selection intensity.
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Affiliation(s)
- Kathryn B McNamara
- Centre for Evolutionary Biology, School of Animal Biology (M092), the University of Western Australia, Crawley, 6009, Australia
| | - Stephen P Robinson
- Centre for Evolutionary Biology, School of Animal Biology (M092), the University of Western Australia, Crawley, 6009, Australia
| | - Márta E Rosa
- Department of Evolutionary Zoology and Human Biology, University of Debrecen, Debrecen, H-4032, Hungary.,Department of Ecology, Szent István University, Budapest, H-1077, Hungary
| | - Nadia S Sloan
- Centre for Evolutionary Biology, School of Animal Biology (M092), the University of Western Australia, Crawley, 6009, Australia
| | - Emile van Lieshout
- Centre for Evolutionary Biology, School of Animal Biology (M092), the University of Western Australia, Crawley, 6009, Australia
| | - Leigh W Simmons
- Centre for Evolutionary Biology, School of Animal Biology (M092), the University of Western Australia, Crawley, 6009, Australia
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26
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Altitude underlies variation in the mating system, somatic condition, and investment in reproductive traits in male Asian grass frogs (Fejervarya limnocharis). Behav Ecol Sociobiol 2016. [DOI: 10.1007/s00265-016-2128-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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27
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Affiliation(s)
- G. A. Parker
- Institute of Integrative Biology; University of Liverpool; Liverpool UK
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28
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Bretman A, Fricke C, Westmancoat JD, Chapman T. Effect of competitive cues on reproductive morphology and behavioral plasticity in male fruitflies. Behav Ecol 2015; 27:452-461. [PMID: 27004011 PMCID: PMC4797378 DOI: 10.1093/beheco/arv170] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 09/17/2015] [Accepted: 09/17/2015] [Indexed: 11/13/2022] Open
Abstract
Phenotypic plasticity will be favored whenever there are significant fitness benefits of responding to environmental variation. The extent and nature of the plasticity that evolves depends on the rate of environmental fluctuations and the capacity to track and respond to that variability. Reproductive environments represent one arena in which changes can be rapid. The finding that males of many species show morphological, physiological, and behavioral plasticity in response to premating and postmating reproductive competition (RC) suggests that plasticity is broadly beneficial. The developmental environment is expected to accurately predict the average population level of RC but to be a relatively poor indicator of immediate RC at any particular mating. Therefore, we predict that manipulation of average RC during development should cause a response in plasticity "set" during development (e.g., size of adult reproductive structures), but not in flexible plasticity determined by the immediate adult environment (e.g., behavioral plasticity in mating duration). We tested this prediction in Drosophila melanogaster males by manipulating 2 independent cues of average RC during development: 1) larval density and 2) the presence or absence of adult males within larval culture vials. Consistent with the prediction, both manipulations resulted in the development of males with significantly larger adult accessory glands (although testis size decreased when males were added to culture vials). There was no effect on adult plasticity (mating duration, extended mating in response to rivals). The results suggest that males have evolved independent responses to long- and short-term variation in RC.
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Affiliation(s)
- Amanda Bretman
- School of Biology, University of Leeds , Manton Building, Leeds LS2 9JT , UK
| | - Claudia Fricke
- Institute for Evolution and Biodiversity, University of Muenster , Huefferstr. 1, 48149 Muenster , Germany , and
| | - James D Westmancoat
- School of Biological Sciences, University of East Anglia , Norwich Research Park, Norwich NR4 7TJ , UK
| | - Tracey Chapman
- School of Biological Sciences, University of East Anglia , Norwich Research Park, Norwich NR4 7TJ , UK
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29
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Pintus E, Ros-Santaella JL, Garde JJ. Beyond Testis Size: Links between Spermatogenesis and Sperm Traits in a Seasonal Breeding Mammal. PLoS One 2015; 10:e0139240. [PMID: 26430740 PMCID: PMC4592251 DOI: 10.1371/journal.pone.0139240] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Accepted: 09/10/2015] [Indexed: 01/21/2023] Open
Abstract
Spermatogenesis is a costly process that is expected to be under selection to maximise sperm quantity and quality. Testis size is often regarded as a proxy measure of sperm investment, implicitly overlooking the quantitative assessment of spermatogenesis. An enhanced understanding of testicular function, beyond testis size, may reveal further sexual traits involved in sperm quantity and quality. Here, we first estimated the inter-male variation in testicular function and sperm traits in red deer across the breeding and non-breeding seasons. Then, we analysed the relationships between the testis mass, eight parameters of spermatogenic function, and seven parameters of sperm quality. Our findings revealed that the Sertoli cell number and function parameters vary greatly between red deer males, and that spermatogenic activity co-varies with testis mass and sperm quality across the breeding and non-breeding seasons. For the first time in a seasonal breeder, we found that not only is the Sertoli cell number important in determining testis mass (r = 0.619, p = 0.007 and r = 0.248, p = 0.047 for the Sertoli cell number assessed by histology and cytology, respectively), but also sperm function (r = 0.703, p = 0.002 and r = 0.328, p = 0.012 for the Sertoli cell number assessed by histology and cytology, respectively). Testicular histology also revealed that a high Sertoli cell number per tubular cross-section is associated with high sperm production (r = 0.600, p = 0.009). Sperm production and function were also positively correlated (r = 0.384, p = 0.004), suggesting that these traits co-vary to maximise sperm fertilisation ability in red deer. In conclusion, our findings contribute to the understanding of the dynamics of spermatogenesis, and reveal new insights into the role of testicular function and the Sertoli cell number on testis size and sperm quality in red deer.
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Affiliation(s)
- Eliana Pintus
- Department of Veterinary Clinics and Pathology, Faculty of Veterinary Medicine, University of Sassari, Sassari, Italy
- Department of Veterinary Sciences, Faculty of Agrobiology, Food and Natural Resources, Czech University of Life Sciences, Prague, Czech Republic
| | - José Luis Ros-Santaella
- Department of Animal Science and Food Processing, Faculty of Tropical AgriSciences, Czech University of Life Sciences, Prague, Czech Republic
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Higginson DM, Badyaev AV, Segraves KA, Pitnick S. Causes of Discordance between Allometries at and above Species Level: An Example with Aquatic Beetles. Am Nat 2015; 186:176-86. [DOI: 10.1086/682049] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Rowe M, Albrecht T, Cramer ERA, Johnsen A, Laskemoen T, Weir JT, Lifjeld JT. Postcopulatory sexual selection is associated with accelerated evolution of sperm morphology. Evolution 2015; 69:1044-52. [PMID: 25655075 DOI: 10.1111/evo.12620] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 01/16/2015] [Indexed: 01/31/2023]
Abstract
Rapid diversification of sexual traits is frequently attributed to sexual selection, though explicit tests of this hypothesis remain limited. Spermatozoa exhibit remarkable variability in size and shape, and studies report a correlation between sperm morphology (sperm length and shape) and sperm competition risk or female reproductive tract morphology. However, whether postcopulatory processes (e.g., sperm competition and cryptic female choice) influence the speed of evolutionary diversification in sperm form is unknown. Using passerine birds, we quantified evolutionary rates of sperm length divergence among lineages (i.e., species pairs) and determined whether these rates varied with the level of sperm competition (estimated as relative testes mass). We found that relative testes mass was significantly and positively associated with more rapid phenotypic divergence in sperm midpiece and flagellum lengths, as well as total sperm length. In contrast, there was no association between relative testes mass and rates of evolutionary divergence in sperm head size, and models suggested that head length is evolutionarily constrained. Our results are the first to show an association between the strength of sperm competition and the speed of sperm evolution, and suggest that postcopulatory sexual selection promotes rapid evolutionary diversification of sperm morphology.
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Affiliation(s)
- Melissah Rowe
- Natural History Museum, University of Oslo, PO Box 1172, Blindern, 0318, Oslo, Norway; Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, PO Box 1066, Blindern, 0316, Oslo, Norway.
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Abe J, Kamimura Y. Sperm economy between female mating frequency and male ejaculate allocation. Am Nat 2015; 185:406-16. [PMID: 25674694 DOI: 10.1086/679586] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Why females of many species mate multiply is a major question in evolutionary biology. Furthermore, if females accept matings more than once, ejaculates from different males compete for fertilization (sperm competition), which confronts males with the decision of how to allocate their reproductive resources to each mating event. Although most existing models have examined either female mating frequency or male ejaculate allocation while assuming fixed levels of the opposite sex's strategies, these strategies are likely to coevolve. To investigate how the interaction of the two sexes' strategies is influenced by the level of sperm limitation in the population, we developed models in which females adjust their number of allowable matings and males allocate their ejaculate in each mating. Our model predicts that females mate only once or less than once at an even sex ratio or in an extremely female-biased condition, because of female resistance and sperm limitation in the population, respectively. However, in a moderately female-biased condition, males favor partitioning their reproductive budgets across many females, whereas females favor multiple matings to obtain sufficient sperm, which contradicts the predictions of most existing models. We discuss our model's predictions and relationships with the existing models and demonstrate applications for empirical findings.
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Affiliation(s)
- Jun Abe
- Department of Biology, Kanagawa University, Hiratsuka, Kanagawa 259-1293, Japan
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Booksmythe I, Fritzsche K, Arnqvist G. Sperm competition generates evolution of increased paternal investment in a sex role-reversed seed beetle. J Evol Biol 2014; 27:2841-9. [DOI: 10.1111/jeb.12549] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Revised: 11/10/2014] [Accepted: 11/10/2014] [Indexed: 11/28/2022]
Affiliation(s)
- I. Booksmythe
- Animal Ecology; Department of Evolution and Genetics; Evolutionary Biology Centre; Uppsala University; Uppsala Sweden
| | - K. Fritzsche
- Animal Ecology; Department of Evolution and Genetics; Evolutionary Biology Centre; Uppsala University; Uppsala Sweden
| | - G. Arnqvist
- Animal Ecology; Department of Evolution and Genetics; Evolutionary Biology Centre; Uppsala University; Uppsala Sweden
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Ramm SA, Schärer L, Ehmcke J, Wistuba J. Sperm competition and the evolution of spermatogenesis. Mol Hum Reprod 2014; 20:1169-79. [PMID: 25323971 DOI: 10.1093/molehr/gau070] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Spermatogenesis is a long and complex process that, despite the shared overall goal of producing the male gamete, displays striking amounts of interspecific diversity. In this review, we argue that sperm competition has been an important selection pressure acting on multiple aspects of spermatogenesis, causing variation in the number and morphology of sperm produced, and in the molecular and cellular processes by which this happens. We begin by reviewing the basic biology of spermatogenesis in some of the main animal model systems to illustrate this diversity, and then ask to what extent this variation arises from the evolutionary forces acting on spermatogenesis, most notably sperm competition. We explore five specific aspects of spermatogenesis from an evolutionary perspective, namely: (i) interspecific diversity in the number and morphology of sperm produced; (ii) the testicular organizations and stem cell systems used to produce them; (iii) the large number and high evolutionary rate of genes underpinning spermatogenesis; (iv) the repression of transcription during spermiogenesis and its link to the potential for haploid selection; and (v) the phenomenon of selection acting at the level of the germline. Overall we conclude that adopting an evolutionary perspective can shed light on many otherwise opaque features of spermatogenesis, and help to explain the diversity of ways in which males of different species perform this fundamentally important process.
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Affiliation(s)
- Steven A Ramm
- Evolutionary Biology, Bielefeld University, Morgenbreede 45, 33615 Bielefeld, Germany
| | - Lukas Schärer
- Evolutionary Biology, Zoological Institute, University of Basel, Vesalgasse 1, 4051 Basel, Switzerland
| | - Jens Ehmcke
- Central Animal Facility of the Faculty of Medicine, University of Münster, Albert-Schweitzer-Campus 1 (A8), 48149 Münster, Germany
| | - Joachim Wistuba
- Institute of Reproductive and Regenerative Biology, Centre of Reproductive Medicine and Andrology, University of Münster, Albert-Schweitzer-Campus 1 (D11), 48149 Münster, Germany
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Vrech DE, Olivero PA, Mattoni CI, Peretti AV. Testes mass, but not sperm length, increases with higher levels of polyandry in an ancient sex model. PLoS One 2014; 9:e94135. [PMID: 24736525 PMCID: PMC3988103 DOI: 10.1371/journal.pone.0094135] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 03/14/2014] [Indexed: 11/26/2022] Open
Abstract
There is strong evidence that polyandrous taxa have evolved relatively larger testes than monogamous relatives. Sperm size may either increase or decrease across species with the risk or intensity of sperm competition. Scorpions represent an ancient direct mode with spermatophore-mediated sperm transfer and are particularly well suited for studies in sperm competition. This work aims to analyze for the first time the variables affecting testes mass, ejaculate volume and sperm length, according with their levels of polyandry, in species belonging to the Neotropical family Bothriuridae. Variables influencing testes mass and sperm length were obtained by model selection analysis using corrected Akaike Information Criterion. Testes mass varied greatly among the seven species analyzed, ranging from 1.6 ± 1.1 mg in Timogenes dorbignyi to 16.3 ± 4.5 mg in Brachistosternus pentheri with an average of 8.4 ± 5.0 mg in all the species. The relationship between testes mass and body mass was not significant. Body allocation in testes mass, taken as Gonadosomatic Index, was high in Bothriurus cordubensis and Brachistosternus ferrugineus and low in Timogenes species. The best-fitting model for testes mass considered only polyandry as predictor with a positive influence. Model selection showed that body mass influenced sperm length negatively but after correcting for body mass, none of the variables analyzed explained sperm length. Both body mass and testes mass influenced spermatophore volume positively. There was a strong phylogenetic effect on the model containing testes mass. As predicted by the sperm competition theory and according to what happens in other arthropods, testes mass increased in species with higher levels of sperm competition, and influenced positively spermatophore volume, but data was not conclusive for sperm length.
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Affiliation(s)
- David E. Vrech
- Institute of Animal Diversity and Ecology (IDEA), Laboratory of Reproductive Biology and Evolution, CONICET - The National University of Cordoba, Cordoba, Argentina
| | - Paola A. Olivero
- Institute of Animal Diversity and Ecology (IDEA), Laboratory of Reproductive Biology and Evolution, CONICET - The National University of Cordoba, Cordoba, Argentina
| | - Camilo I. Mattoni
- Institute of Animal Diversity and Ecology (IDEA), Laboratory of Reproductive Biology and Evolution, CONICET - The National University of Cordoba, Cordoba, Argentina
| | - Alfredo V. Peretti
- Institute of Animal Diversity and Ecology (IDEA), Laboratory of Reproductive Biology and Evolution, CONICET - The National University of Cordoba, Cordoba, Argentina
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Ferrandiz-Rovira M, Lemaître JF, Lardy S, López BC, Cohas A. Do pre- and post-copulatory sexually selected traits covary in large herbivores? BMC Evol Biol 2014; 14:79. [PMID: 24716470 PMCID: PMC4026391 DOI: 10.1186/1471-2148-14-79] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Accepted: 03/13/2014] [Indexed: 12/30/2022] Open
Abstract
Background In most species, males compete to gain both matings (via pre-copulatory competition) and fertilizations (via post-copulatory competition) to maximize their reproductive success. However, the quantity of resources devoted to sexual traits is finite, and so males are predicted to balance their investment between pre- and post-copulatory expenditure depending on the expected pay-offs that should vary according to mating tactics. In Artiodactyla species, males can invest in weapons such as horns or antlers to increase their mating gains or in testes mass/sperm dimensions to increase their fertilization efficiency. Moreover, it has been suggested that in these species, males with territory defence mating tactic might preferentially increase their investment in post-copulatory traits to increase their fertilization efficiency whereas males with female defence mating tactic might increase their investment in pre-copulatory sexually selected traits to prevent other males from copulating with females. In this study, we thus test the prediction that male’s weapon length (pre-copulatory trait) covaries negatively with relative testes size and/or sperm dimensions (post-copulatory traits) across Artiodactyla using a phylogenetically controlled framework. Results Surprisingly no association between weapon length and testes mass is found but a negative association between weapon length and sperm length is evidenced. In addition, neither pre- nor post-copulatory traits were found to be affected by male mating tactics. Conclusions We propose several hypotheses that could explain why male ungulates may not balance their reproductive investment between pre- and post-copulatory traits.
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Affiliation(s)
| | | | | | | | - Aurélie Cohas
- Laboratoire Biométrie et Biologie Evolutive, Université de Lyon, CNRS, UMR5558, Université Lyon 1, F-69622, Villeurbanne, F-69000 Lyon, France.
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Engqvist L, Cordes N, Schwenniger J, Bakhtina S, Schmoll T. Female Remating Behavior in a Lekking Moth. Ethology 2014. [DOI: 10.1111/eth.12237] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Leif Engqvist
- Evolutionary Biology; Bielefeld University; Bielefeld Germany
| | - Nils Cordes
- Evolutionary Biology; Bielefeld University; Bielefeld Germany
| | | | | | - Tim Schmoll
- Evolutionary Biology; Bielefeld University; Bielefeld Germany
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Lüpold S, Tomkins JL, Simmons LW, Fitzpatrick JL. Female monopolization mediates the relationship between pre- and postcopulatory sexual traits. Nat Commun 2014; 5:3184. [DOI: 10.1038/ncomms4184] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 12/31/2013] [Indexed: 11/09/2022] Open
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40
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van der Horst G, Maree L. Sperm form and function in the absence of sperm competition. Mol Reprod Dev 2013; 81:204-16. [DOI: 10.1002/mrd.22277] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Accepted: 10/30/2013] [Indexed: 01/08/2023]
Affiliation(s)
- Gerhard van der Horst
- Department of Medical Bioscience; University of the Western Cape; Bellville South Africa
| | - Liana Maree
- Department of Medical Bioscience; University of the Western Cape; Bellville South Africa
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Janicke T, Marie-Orleach L, De Mulder K, Berezikov E, Ladurner P, Vizoso DB, Schärer L. Sex allocation adjustment to mating group size in a simultaneous hermaphrodite. Evolution 2013; 67:3233-42. [PMID: 24152005 DOI: 10.1111/evo.12189] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Accepted: 05/22/2013] [Indexed: 11/29/2022]
Abstract
Sex allocation theory is considered as a touchstone of evolutionary biology, providing some of the best supported examples for Darwinian adaptation. In particular, Hamilton's local mate competition theory has been shown to generate precise predictions for extraordinary sex ratios observed in many separate-sexed organisms. In analogy to local mate competition, Charnov's mating group size model predicts how sex allocation in simultaneous hermaphrodites is affected by the mating group size (i.e., the number of mating partners plus one). Until now, studies have not directly explored the relationship between mating group size and sex allocation, which we here achieve in the simultaneously hermaphroditic flatworm Macrostomum lignano. Using transgenic focal worms with ubiquitous expression of green-fluorescent protein (GFP), we assessed the number of wild-type mating partners carrying GFP+ sperm from these focal worms when raised in different social group sizes. This allowed us to test directly how mating group size was related to the sex allocation of focal worms. We find that the proportion of male investment initially increases with increasing mating group size, but then saturates as predicted by theory. To our knowledge, this is the first direct test of the mating group size model in a simultaneously hermaphroditic animal.
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Affiliation(s)
- Tim Janicke
- Zoological Institute, University of Basel, Switzerland; Centre d'Écologie Fonctionnelle et Évolutive, Montpellier, France.
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McNamara KB, Wedell N, Simmons LW. Experimental evolution reveals trade-offs between mating and immunity. Biol Lett 2013; 9:20130262. [PMID: 23720521 PMCID: PMC3730636 DOI: 10.1098/rsbl.2013.0262] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Immune system maintenance and upregulation is costly. Sexual selection intensity, which increases male investment into reproductive traits, is expected to create trade-offs with immune function. We assayed phenoloxidase (PO) and lytic activity of individuals from populations of the Indian meal moth, Plodia interpunctella, which had been evolving under different intensities of sexual selection. We found significant divergence among populations, with males from female-biased populations having lower PO activity than males from balanced sex ratio or male-biased populations. There was no divergence in anti-bacterial lytic activity. Our data suggest that it is the increased male mating demands in female-biased populations that trades-off against immunity, and not the increased investment in sperm transfer per mating that characterizes male-biased populations.
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Affiliation(s)
- Kathryn B McNamara
- Centre for Evolutionary Biology, The University of Western Australia, Crawley 6009, Australia.
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Lüpold S. Ejaculate quality and constraints in relation to sperm competition levels among eutherian mammals. Evolution 2013; 67:3052-60. [PMID: 24094354 DOI: 10.1111/evo.12132] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2012] [Accepted: 04/05/2013] [Indexed: 01/21/2023]
Abstract
The outcome of sperm competition is influenced by the relative quantity and quality of sperm among competing ejaculates. Whereas it is well established that individual ejaculate traits evolve rapidly under postcopulatory sexual selection, little is known about other factors that might influence the evolution of ejaculates. For example, the metabolic rate is likely to affect the sperm production rate and the cellular activity or metabolism of sperm, and it has recently been suggested to constrain the evolution of sperm length in large but not small mammals. I thus examined in eutherian mammals how ejaculate quality traits vary with one another and with testis mass, body size, and metabolism. I found all ejaculate traits to covary positively with one another and to increase with relative testis mass. When controlling for testis mass, small-bodied species showed superior sperm quality (but not sperm number). Furthermore, sperm motility and viability were positively associated with the mass-corrected metabolic rate, but the percentage of morphologically normal and acrosome-intact sperm were not. These results indicate that body size and the energy budget may also influence the evolution of ejaculate quality, although these influences appear to vary among traits.
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Affiliation(s)
- Stefan Lüpold
- Department of Biology, Life Sciences Complex, 107 College Place, Syracuse University, Syracuse, New York, 13244.
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Pérez W, Vazquez N, Ungerfeld R. Gross anatomy of the male genital organs of the pampas deer (Ozotoceros bezoarticus, Linnaeus 1758). Anat Sci Int 2013; 88:123-9. [DOI: 10.1007/s12565-013-0171-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Accepted: 01/18/2013] [Indexed: 11/25/2022]
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Puniamoorthy N, Blanckenhorn WU, Schäfer MA. Differential investment in pre- vs. post-copulatory sexual selection reinforces a cross-continental reversal of sexual size dimorphism inSepsis punctum(Diptera: Sepsidae). J Evol Biol 2012; 25:2253-63. [DOI: 10.1111/j.1420-9101.2012.02605.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2012] [Revised: 07/15/2012] [Accepted: 07/23/2012] [Indexed: 11/28/2022]
Affiliation(s)
| | - W. U. Blanckenhorn
- Institute of Evolutionary Biology and Environmental Studies; University of Zurich; Zurich; Switzerland
| | - M. A. Schäfer
- Institute of Evolutionary Biology and Environmental Studies; University of Zurich; Zurich; Switzerland
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Abstract
Females frequently mate with several males, whose sperm then compete to fertilize available ova. Sperm competition represents a potent selective force that is expected to shape male expenditure on the ejaculate. Here, we review empirical data that illustrate the evolutionary consequences of sperm competition. Sperm competition favors the evolution of increased testes size and sperm production. In some species, males appear capable of adjusting the number of sperm ejaculated, depending on the perceived levels of sperm competition. Selection is also expected to act on sperm form and function, although the evidence for this remains equivocal. Comparative studies suggest that sperm length and swimming speed may increase in response to selection from sperm competition. However, the mechanisms driving this pattern remain unclear. Evidence that sperm length influences sperm swimming speed is mixed and fertilization trials performed across a broad range of species demonstrate inconsistent relationships between sperm form and function. This ambiguity may in part reflect the important role that seminal fluid proteins (sfps) play in affecting sperm function. There is good evidence that sfps are subject to selection from sperm competition, and recent work is pointing to an ability of males to adjust their seminal fluid chemistry in response to sperm competition from rival males. We argue that future research must consider sperm and seminal fluid components of the ejaculate as a functional unity. Research at the genomic level will identify the genes that ultimately control male fertility.
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Affiliation(s)
- Leigh W Simmons
- Centre for Evolutionary Biology, , School of Animal Biology (M092), The University of Western Australia, Crawley, Western Australia 6009, Australia.
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