Sexual selection, phenotypic plasticity and female reproductive output

Abstract

One contribution of 13 to a theme issue 'The role of plasticity in phenotypic adaptation to rapid environmental change'.In a rapidly changing environment, does sexual selection on males elevate a population's reproductive output? If so, does phenotypic plasticity enhance or diminish any such effect? We outline two routes by which sexual selection can influence the reproductive output of a population: a genetic correlation between male sexual competitiveness and female lifetime reproductive success; and direct effects of males on females' breeding success. We then discuss how phenotypic plasticity of sexually selected male traits and/or female responses (e.g. plasticity in mate choice), as the environment changes, might influence how sexual selection affects a population's reproductive output. Two key points emerge. First, condition-dependent expression of male sexual traits makes it likely that sexual selection increases female fitness if reproductively successful males disproportionately transfer genes that are under natural selection in both sexes, such as genes for foraging efficiency. Condition-dependence is a form of phenotypic plasticity if some of the variation in net resource acquisition and assimilation is attributable to the environment rather than solely genetic in origin. Second, the optimal allocation of resources into different condition-dependent traits depends on their marginal fitness gains. As male condition improves, this can therefore increase or, though rarely highlighted, actually decrease the expression of sexually selected traits. It is therefore crucial to understand how condition determines male allocation of resources to different sexually selected traits that vary in their immediate effects on female reproductive output (e.g. ornaments versus coercive behaviour). In addition, changes in the distribution of condition among males as the environment shifts could reduce phenotypic variance in certain male traits, thereby reducing the strength of sexual selection imposed by females. Studies of adaptive evolution under rapid environmental change should consider the possibility that phenotypic plasticity of sexually selected male traits, even if it elevates male fitness, could have a negative effect on female reproductive output, thereby increasing the risk of population extinction.This article is part of the theme issue 'The role of plasticity in phenotypic adaptation to rapid environmental change'.

Dietary stress increases the total opportunity for sexual selection and modifies selection on condition‐dependent traits

“…Numerous studies have reported that individuals whose condition is experimentally manipulated exhibit reduced mean trait expression and reproductive success, leading to an overall increase in the opportunity for sexual selection (Zikovitz & Agrawal ; Martinossi‐Allibert et al ). However, when the whole population experiences a reduction in the resources available for reproduction, whether the opportunity for selection increases will largely depend on the effect of resources on the variance in the expression of sexually selected traits, rather than on their mean (Arbuthnott & Whitlock ; Fox et al ). With a few notable exceptions (David et al ; Howie et al ), studies that test for condition dependence in sexually selected traits tend to focus on trait means rather than variances (Jennions et al ; Cotton et al ).…”

“…A male’s reproductive success will therefore depend on the combined effects of condition on the expression of traits that affect mate acquisition, copulation, and fertilization (Evans & Garcia‐Gonzalez ). The effect of reduced resources might vary among different sexually selected traits in terms of their average expression and their variances, with unpredictable effects on the resulting strength and shape of sexual selection (Fox et al ). Second, adverse environmental conditions will also affect the resources available to females, which in turn may affect their mating decisions/strategies and possibly their fecundity (Cotton et al ; Collet et al ; Parker et al ; Morimoto et al ).…”

“…). However, despite increasing evidence that environmental variability has strong effects on the expression of sexually selected traits (Evans & Garcia‐Gonzalez ), our understanding of the effect of resource availability on the strength of sexual selection on condition‐dependent sexually selected traits is still very limited (Fox et al ). Experiments in controlled conditions indicate that variance in lifetime reproductive success increases with stress, and it is greater in adult males than in females (Martinossi‐Allibert et al ).…”

Direct and indirect effects of sexual signal loss on female reproduction in the Pacific field cricket (Teleogryllus oceanicus)

“…Sexual signals are often expressed in only one sex, typically males, and much research focuses on the drivers of signal diversification and implications for speciation (Martin, Riesch, Heinen‐Kay, & Langerhans, ; Miles, Cheng, & Fuxjager, ; Panhuis, Butlin, Zuk, & Tregenza, ; Safran, Scordato, Symes, Rodriguez, & Mendelson, ; Zuk & Simmons, ). However, sexual signal evolution can pose fitness consequences for the non‐signaling sex, often females, because of shared genes (Berg & Maklakov, ; Harano, Okada, Nakayama, Miyatake, & Hosken, ; Plesnar‐Bielak, Skrzynecka, Miler, & Radwan, ; Tarka, Akesson, Hasselquist, & Hansson, ) and altered social conditions (Fox, Fromhage, & Jennions, ). Alleles underlying male sexual signals can exert negative, beneficial, or neutral effects in females due to pleiotropy or linkage.…”

“…| 1383 HEINEN-KAY Et Al. 2012; Harano, Okada, Nakayama, Miyatake, & Hosken, 2010;Plesnar-Bielak, Skrzynecka, Miler, & Radwan, 2014;Tarka, Akesson, Hasselquist, & Hansson, 2014) and altered social conditions (Fox, Fromhage, & Jennions, 2019). Alleles underlying male sexual signals can exert negative, beneficial, or neutral effects in females due to pleiotropy or linkage.…”