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Chung MHJ, Fox RJ, Jennions MD. Male allocation to ejaculation and mating effort imposes different life history trade-offs. PLoS Biol 2024; 22:e3002519. [PMID: 38787858 DOI: 10.1371/journal.pbio.3002519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2024] [Accepted: 05/13/2024] [Indexed: 05/26/2024] Open
Abstract
When males compete, sexual selection favors reproductive traits that increase their mating or fertilization success (pre- and postcopulatory sexual selection). It is assumed that males face a trade-off between these 2 types of sexual traits because they both draw from the same pool of resources. Consequently, allocation into mate acquisition or ejaculation should create similar trade-offs with other key life history traits. Tests of these assumptions are exceedingly rare. Males only ejaculate after they mate, and the costs of ejaculation are therefore highly confounded with those of mating effort. Consequently, little is known about how each component of reproductive allocation affects a male's future performance. Here, we ran an experiment using a novel technique to distinguish the life history costs of mating effort and ejaculation for mosquitofish (Gambusia holbrooki). We compared manipulated males (mate without ejaculation), control males (mate and ejaculate), and naïve males (neither mate nor ejaculate) continuously housed with a female and 2 rival males. We assessed their growth, somatic maintenance, mating and fighting behavior, and sperm traits after 8 and 16 weeks. Past mating effort significantly lowered a male's future mating effort and growth, but not his sperm production, while past sperm release significantly lowered a male's future ejaculate quantity, but not his mating effort. Immune response was the only trait impacted by both past mating effort and past ejaculation. These findings challenge the assumption that male reproductive allocation draws from a common pool of resources to generate similar life history costs later in life. Instead, we provide clear evidence that allocation into traits under pre- and postcopulatory sexual selection have different trait-specific effects on subsequent male reproductive performance.
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Affiliation(s)
- Meng-Han Joseph Chung
- Division of Ecology and Evolution, Research School of Biology, Australian National University, Canberra, Australia
| | - Rebecca J Fox
- Division of Ecology and Evolution, Research School of Biology, Australian National University, Canberra, Australia
| | - Michael D Jennions
- Division of Ecology and Evolution, Research School of Biology, Australian National University, Canberra, Australia
- Stellenbosch Institute for Advanced Study (STIAS), Wallenberg Research Centre at Stellenbosch University, Stellenbosch, South Africa
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Chung MHJ, Head ML, Fox RJ, Jennions MD. Effects of past mating behavior versus past ejaculation on male mate choice and male attractiveness. Behav Ecol 2024; 35:arae002. [PMID: 38273897 PMCID: PMC10807976 DOI: 10.1093/beheco/arae002] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 12/26/2023] [Accepted: 01/05/2024] [Indexed: 01/27/2024] Open
Abstract
Past reproductive effort allows males to assess their ability to acquire mates, but it also consumes resources that can reduce their future competitive ability. Few studies have examined how a male's reproductive history affects his subsequent mate choice, and, to date, no study has determined the relative contribution of past mating behavior and past ejaculate production because these two forms of investment are naturally highly correlated. Here, we disentangled the relative effects of past mating behavior and past ejaculate production in mosquitofish (Gambusia holbrooki) by experimentally preventing some males from ejaculating when trying to mate. We assessed the effect of mating behavior on mate choice by comparing males that had previously been with or without access to females and male rivals for 8 and 16 weeks and assessed the effect of ejaculation on mate choice by comparing males that either could or could not ejaculate when they had access to females for 16 weeks. Reproductive treatment did not affect male attractiveness, but it did affect male mate choice. Somewhat surprisingly, in five of the six treatment-by-age at testing combinations, males preferred a female in the vicinity of a male rival over a solitary female. This preference was marginally stronger for males that had previously engaged in mating behavior but were unaffected by past ejaculate production. We discuss the potential benefits to males of associating with another male when seeking mates. This is the first study to quantify the relative influence of pre- and post-copulatory reproductive investment on male mate choice.
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Affiliation(s)
- Meng-Han Joseph Chung
- Division of Ecology and Evolution, Research School of Biology, Australian National University, 46 Sullivans Creek Road, Acton, Australian Capital Territory 2600, Australia
| | - Megan L Head
- Division of Ecology and Evolution, Research School of Biology, Australian National University, 46 Sullivans Creek Road, Acton, Australian Capital Territory 2600, Australia
| | - Rebecca J Fox
- Division of Ecology and Evolution, Research School of Biology, Australian National University, 46 Sullivans Creek Road, Acton, Australian Capital Territory 2600, Australia
| | - Michael D Jennions
- Division of Ecology and Evolution, Research School of Biology, Australian National University, 46 Sullivans Creek Road, Acton, Australian Capital Territory 2600, Australia
- Stellenbosch Institute for Advanced Study (STIAS), Wallenberg Centre, 10 Marais Street, Stellenbosch 7600, South Africa
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Chung MHJ, Jennions MD, Fox RJ. Quantifying the costs of pre- and postcopulatory traits for males: Evidence that costs of ejaculation are minor relative to mating effort. Evol Lett 2021; 5:315-327. [PMID: 34367658 PMCID: PMC8327938 DOI: 10.1002/evl3.228] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2021] [Revised: 04/08/2021] [Accepted: 04/12/2021] [Indexed: 12/12/2022] Open
Abstract
Although it is widely stated that both mating behavior and sperm traits are energetically costly for males, we currently lack empirical estimates of the relative costs to males of pre‐ versus postcopulatory investments. Such estimates require the experimental separation of the act of mating from that of ejaculation, which is a nontrivial logistical challenge. Here, we overcome this challenge using a novel morphological manipulation (gonopodium tip ablation) in the eastern mosquitofish (Gambusia holbrooki) to tease apart investment in mating effort from that in sperm replenishment following ejaculation. We quantified the relative cumulative costs of investing in mating effort and ejaculation by comparing somatic traits and reproductive performance among three types of males: ablated males that could attempt to mate but not ejaculate; unablated males that could both mate and ejaculate; and control males that had no access to females. We show that, after eight weeks, mating investment significantly reduces both body growth and immunocompetence and results in a significant decline in mating effort. In contrast, cumulative investment into sperm replenishment following ejaculation has few detectable effects that are only apparent in smaller males. These minor costs occur despite the fact that G. holbrooki has very high levels of sperm competition and multiple mating by both sexes, which is usually associated with elevated levels of sperm production. Crucially, our study is the first, to our knowledge, to experimentally compare the relative costs of pre‐ and postcopulatory investment on components of male fitness in a vertebrate.
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Affiliation(s)
- Meng-Han Joseph Chung
- Division of Ecology and Evolution Research School of Biology Australian National University Canberra ACT 2601 Australia
| | - Michael D Jennions
- Division of Ecology and Evolution Research School of Biology Australian National University Canberra ACT 2601 Australia
| | - Rebecca J Fox
- Division of Ecology and Evolution Research School of Biology Australian National University Canberra ACT 2601 Australia
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Chen S, Lin C, Tan J, Wang Y, Wang X, Wang X, Liu L, Li J, Hou L, Liu J, Leung JYS. Reproductive potential of mosquitofish is reduced by the masculinizing effect of a synthetic progesterone, gestodene: Evidence from morphology, courtship behaviour, ovary histology, sex hormones and gene expressions. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 769:144570. [PMID: 33486178 DOI: 10.1016/j.scitotenv.2020.144570] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2020] [Revised: 12/08/2020] [Accepted: 12/13/2020] [Indexed: 06/12/2023]
Abstract
The ever-increasing use of synthetic hormones, especially progestins, for medical applications has drawn growing concerns due to their potential endocrine disrupting effects that may diminish the reproductive outputs of aquatic organisms. Using mosquitofish (Gambusia affinis) as a model species, we tested whether gestodene (GES), a commonly used progestin, can alter the expressions of genes associated with sex hormone synthesis and cause ensuing changes in morphological features, courtship behaviour and oocyte development. After exposing to GES at environmentally relevant concentrations (2.96, 32.9 and 354 ng L-1) for 40 days, we found that GES, especially at 354 ng L-1, induced masculinization of female fish, indicated by the reduced body weight to length ratio and development of gonopodia (i.e. anal fins of male fish). Thus, the males showed less intimacy and mating interest towards the GES-exposed females, indicated by the reduced time spent on attending, following and mating behaviours. While oocyte development was seemingly unaffected by GES, spermatogonia were developed in the ovary. All the aforementioned masculinizing effects of GES were associated with the increased testosterone level and decreased estradiol level, driven by upregulating androgen receptor genes (Arα and Arβ). Overall, our findings suggest that progestins could undermine the reproductive potential of aquatic organisms and hence their persistence in the progestin-contaminated environment.
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Affiliation(s)
- Shanduo Chen
- School of Life Sciences, Guangzhou University, Guangzhou 510655, China
| | - Canyuan Lin
- Ministry of Education Key Laboratory of Pollution Control and Ecological Remediation for Industrial Agglomeration Area, School of Environment and Energy, South China University of Technology, Guangzhou 510006, China
| | - Jiefeng Tan
- School of Life Sciences, Guangzhou University, Guangzhou 510655, China
| | - Yifan Wang
- School of Life Sciences, Guangzhou University, Guangzhou 510655, China
| | - Xiaoyun Wang
- State Key Laboratory of Biocontrol, College of Ecology and Evolution, School of Life Sciences, Sun Yat-sen University, Guangzhou 510275, China
| | - Xiaolan Wang
- School of Life Sciences, Guangzhou University, Guangzhou 510655, China
| | - Lu Liu
- School of Life Sciences, Guangzhou University, Guangzhou 510655, China
| | - Jiayi Li
- School of Life Sciences, Guangzhou University, Guangzhou 510655, China
| | - Liping Hou
- School of Life Sciences, Guangzhou University, Guangzhou 510655, China.
| | - Juan Liu
- Key Laboratory of Water Quality and Conservation in the Pearl River Delta, Ministry of Education, Guangdong Provincial Key Laboratory of Radionuclides Pollution, China.
| | - Jonathan Y S Leung
- Faculty of Materials and Energy, Southwest University, Chongqing 400715, China; School of Biological Sciences, The University of Adelaide, Adelaide 5005, Australia.
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Langerhans RB, Rosa-Molinar E. A Novel Body Plan Alters Diversification of Body Shape and Genitalia in Live-Bearing Fish. Front Ecol Evol 2021. [DOI: 10.3389/fevo.2021.619232] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Major evolutionary innovations can greatly influence subsequent evolution. While many major transitions occurred in the deep past, male live-bearing fishes (family Poeciliidae) more recently evolved a novel body plan. This group possesses a three-region axial skeleton, with one region—the ano-urogenital region—representing a unique body region accommodating male genitalic structures (gonopodial complex). Here we evaluate several hypotheses for the evolution of diversity in this region and examine its role in the evolution of male body shape. Examining Gambusia fishes, we tested a priori predictions for (1) joint influence of gonopodial-complex traits on mating performance, (2) correlated evolution of gonopodial-complex traits at macro- and microevolutionary scales, and (3) predator-driven evolution of gonopodial-complex traits in a post-Pleistocene radiation of Bahamas mosquitofish. We found the length of the sperm-transfer organ (gonopodium) and its placement along the body (gonopodial anterior transposition) jointly influenced mating success, with correlational selection favoring particular trait combinations. Despite these two traits functionally interacting during mating, we found no evidence for their correlated evolution at macro- or microevolutionary scales. In contrast, we did uncover correlated evolution of modified vertebral hemal spines (part of the novel body region) and gonopodial anterior transposition at both evolutionary scales, matching predictions of developmental connections between these components. Developmental linkages in the ano-urogenital region apparently play key roles in evolutionary trajectories, but multiple selective agents likely act on gonopodium length and cause less predictable evolution. Within Bahamas mosquitofish, evolution of hemal-spine morphology, and gonopodial anterior transposition across predation regimes was quite predictable, with populations evolving under high predation risk showing more modified hemal spines with greater modifications and a more anteriorly positioned gonopodium. These changes in the ano-urogenital vertebral region have facilitated adaptive divergence in swimming abilities and body shape between predation regimes. Gonopodium surface area, but not length, evolved as predicted in Bahamas mosquitofish, consistent with a previously suggested tradeoff between natural and sexual selection on gonopodium size. These results provide insight into how restructured body plans offer novel evolutionary solutions. Here, a novel body region—originally evolved to aid sperm transfer—was apparently co-opted to alter whole-organism performance, facilitating phenotypic diversification.
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