Are sexually selected traits affected by a poor environment early in life?

Vega‐Trejo, Regina; Jennions, Michael D.; Head, Megan L.

doi:10.1101/045740

Cited by 16 publications

(27 citation statements)

References 87 publications

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“…). Elsewhere we have shown that, controlling for age, a poor juvenile diet reduces sperm reserves and sperm replenishment rates in younger male G. holbrooki (Vega‐Trejo, Jennions & Head ). The males in our current experiment were, however, sufficiently old (28–37 weeks post‐maturation) that juvenile diets should not have affected sperm production.…”

Section: Discussionmentioning

confidence: 86%

Experimental evidence for sexual selection against inbred males

Vega‐Trejo

Head

Keogh

et al. 2017

Journal of Animal Ecology

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The detrimental effects of matings between relatives are well known. However, few studies determine the extent to which inbreeding depression in males is due to natural or sexual selection. Importantly, measuring fitness or key fitness components, rather than phenotypic traits allows more accurate estimation of inbreeding depression. We investigate how differences in inbreeding and juvenile diet (i.e. early stressful environment) influence a key component of male fitness, namely their reproductive success. We experimentally created inbred and outbred male mosquitofish (Gambusia holbrooki) by mating full-sibs (f = 0·25). We show that this led to a 23% reduction in genome-wide heterozygosity based on SNPs. Males were raised on different diets early in life to create high-stress and low-stress rearing environments. We then allowed adult males to compete freely for females to test if inbreeding, early diet and their interaction affect a male's share of paternity. Early diet had no effect on paternity, but outbred males sired almost twice as many offspring as inbred males (n = 628 offspring from 122 potential sires). Using artificial insemination methods we determined that this was unlikely to be due to early embryo mortality of eggs fertilised by inbred males: there was no evidence that male inbreeding status affects the realised fecundity of females (n = 288). Given there was no difference in male mortality in our competitive mating experiment, the lower reproductive success of inbred males can most parsimoniously be attributed to inbreeding negatively affecting sexually selected traits that affect male mating success and/or sperm competitiveness. We discuss which sexually selected traits might be involved.

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Section: Discussionmentioning

confidence: 86%

Experimental evidence for sexual selection against inbred males

Vega‐Trejo

Head

Keogh

et al. 2017

Journal of Animal Ecology

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“…We then quantified two ejaculate traits: sperm number and velocity. For sperm collection and measurement, we followed the methods of Vega‐Trejo, Jennions, and Head (). Briefly, we stripped sperm and collected two subsamples each containing three sperm bundles.…”

Section: Methodsmentioning

confidence: 99%

An experimental test for body size‐dependent effects of male harassment and an elevated copulation rate on female lifetime fecundity and offspring performance

Iglesias‐Carrasco

Fox

Vega‐Trejo

et al. 2019

J of Evolutionary Biology

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Many studies investigate the benefits of polyandry, but repeated interactions with males can lower female reproductive success. Interacting with males might even decrease offspring performance if it reduces a female's ability to transfer maternal resources. Male presence can be detrimental for females in two ways: by forcing females to mate at a higher rate and through costs associated with resisting male mating attempts. Teasing apart the relative costs of elevated mating rates from those of greater male harassment is critical to understand the evolution of mating strategies. Furthermore, it is important to test whether a male's phenotype, notably body size, has differential effects on female reproductive success versus the performance of offspring, and whether this is due to male body size affecting the costs of harassment or the actual mating rate. In the eastern mosquitofish Gambusia holbrooki, males vary greatly in body size and continually attempt to inseminate females. We experimentally manipulated male presence (i.e., harassment), male body size and whether males could copulate. Exposure to males had strong detrimental effects on female reproductive output, growth and immune response, independent of male size or whether males could copulate. In contrast, there was a little evidence of a cross‐generational effect of male harassment or mating rate on offspring performance. Our results suggest that females housed with males pay direct costs due to reduced condition and offspring production and that these costs are not a consequence of increased mating rates. Furthermore, exposure to males does not affect offspring reproductive traits.

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“…While many studies have indeed demonstrated condition-dependent responses of male sperm and semen traits through experiments manipulating nutrient availability (e.g. Droney, 1998;Rahman, Kelley, & Evans, 2013;Vega-Trejo, Jennions, & Head, 2016;Dávila & Aron, 2017), some studies have found that males may increase their investment in ejaculate traits when nutrients are reduced (e.g. Simmons, Tomkins, & Hunt, 1999;Perry & Rowe, 2010;Mehlis et al, 2015), while others have found no effect of diet on such traits (e.g.…”

Section: (2) Special Challenges In Research On Ejaculate Condition Dementioning

confidence: 99%

“…Many such studies have manipulated total calories without altering nutrient ratios (e.g. Vermeulen, Engels, & Sauer, 2008;Kahrl & Cox, 2015;Mehlis et al, 2015;Kaldun & Otti, 2016;Vega-Trejo et al, 2016). However, particular macro-or micronutrients may be particularly important for ejaculate trait expression.…”

Section: ) Sources Of Variation In Ejaculate Condition Dependencementioning

confidence: 99%

Effects of nutrient limitation on sperm and seminal fluid: a systematic review and meta‐analysis

et al. 2019

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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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Are sexually selected traits affected by a poor environment early in life?

Cited by 16 publications

References 87 publications

Experimental evidence for sexual selection against inbred males

Experimental evidence for sexual selection against inbred males

An experimental test for body size‐dependent effects of male harassment and an elevated copulation rate on female lifetime fecundity and offspring performance

Effects of nutrient limitation on sperm and seminal fluid: a systematic review and meta‐analysis

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