Evolution of female choice under intralocus sexual conflict and genotype-by-environment interactions

Abstract

In many species, females are hypothesized to obtain 'good genes' for their offspring by mating with males in good condition. However, female preferences might deplete genetic variance and make choice redundant. Additionally, high-condition males sometimes produce low-fitness offspring, for example because of environmental turnover and gene-by-environment interactions (GEIs) for fitness, or because fit males carry sexually antagonistic alleles causing them to produce unfit daughters. Here, we extend previous theory by investigating the evolution of female mate choice in a spatially explicit evolutionary simulation implementing both GEIs and intralocus sexual conflict (IASC), under sex-specific hard or soft selection. We show that IASC can weaken female preferences for high-condition males or even cause a preference for males in low condition, depending on the relative benefits of producing well-adapted sons versus daughters, which in turn depends on the relative hardness of selection on males and females. We discuss the relevance of our results to conservation genetics and empirical evolutionary biology.This article is part of the theme issue 'Linking local adaptation with the evolution of sex differences'.

Meta-analytic evidence that sexual selection improves population fitness

“…This explanation may initially seem implausible, because net selection on males is often stronger than on females 47 , due in part to the elevated importance of sexual selection in males as opposed to females 53–56 . However, an oft-overlooked aspect is that selection might frequently be softer on males and harder on females 57 , because the local competitive environment is usually more important for males than it is for females. For instance, a mediocre male genotype can have high fitness provided it outcompetes its local rivals, while low-fitness female genotypes might produce few offspring even when competing with other low-fitness females.…”

Sexual selection, phenotypic plasticity and female reproductive output

“…So male mating success is potentially correlated with additive genetic variation for naturally selected traits that benefit females, thereby making r G positive if condition-enhancing genes elevate both male mating success and female LRS. Phrased slightly differently, condition-dependent traits provide a mechanism whereby sexual selection can eliminate deleterious alleles from a population, regardless of whether they arise owing to mutations, gene flow between locally adapted populations [13,105,106], or mismatch due to environmental change ( [5,107]; but see [108]). The existence of condition-dependent, sexually selected male traits might therefore seem likely to elevate mean female LRS because of the genetic benefits to females of mating with males in good condition.…”

“…Unfortunately, most theoretical studies of how sexual selection facilitates adaptation implicitly assume that sexually selected traits are conditiondependent. This is because it is the only obvious mechanism to link the process of females disproportionately mating with males with greater investment in sexually selected traits (usually modelled assuming female choice) to genetic benefits that elevate female reproductive success [13,45,46,106]. However, this approach precludes answering the broader question of whether r G is more positive, sexual trait heritability (h 2 ¼ V A /V P ) is higher, or S is larger in a novel environment if sexually selected traits are phenotypically plastic instead of fixed in expression (i.e.…”

“…Before proceeding further, we should acknowledge that mean female lifetime reproductive success (LRS) is an imperfect proxy for the realized growth of a population and its effective population size (the two key demographic parameters that influence extinction risk (review: [11]; see also [12])). We are essentially assuming there is 'hard' rather than 'soft' selection on female LRS (see [13]) such that absolute differences in female LRS between a population with and without sexual selection translate into differential recruitment rates. This is a simplification, but one that is widely used when investigating so-called 'population fitness' (e.g.…”

Direct and indirect selection on mate choice during pollen competition: Effects of male and female sexual traits on offspring performance following two‐donor crosses

“…This could potentially lead to selection for direct benefits by the loss of mate choice or mate choice for early fertilizing pollen, thereby avoiding costs of the sexual conflict over stigma receptivity (cf. Li & Holman, 2018). In previous crosses at early floral stages in C. heterophylla , in which pollen competitors arrived sequentially, early rather than late stigma receptivity was related to the highest maternal seed production (Lankinen & Strandh, 2016).…”