The strength of sex‐specific selection in the wild

Abstract

Anisogamy predisposes the sexes to very different patterns of selection on shared traits. Selective differences between the sexes may manifest as changes in the direction or strength of selection acting on shared phenotypes. Although previous studies havefound evidence for widespread differences in the direction of selection between the sexes, surprisingly little is known regarding potential differences in the magnitude of selection and whether such differences might be confined to specific components of fitness. We conducted a meta-analysis using 865 estimates of phenotypic selection from wild populations to characterize sex differences in the strength of selection and to ask whether different components of fitness exhibit differences in sex bias in the strength of selection. Overall, consistent with past results, we find evidence of male bias in the strength of selection, driven primarily by components of fitness related to mating success and we discuss several evolutionary implications. K E Y W O R D S : meta-analysis, natural selection, phenotypic selection, selection gradients, sexual conflict, sexual selection, sexually antagonistic selection.

Heat knockdown resistance and chill‐coma recovery as correlated responses to selection on mating success at high temperature in Drosophila buzzatii

“…Mean values (± SE) of chill-coma recovery (CCR) are shown for each sex with a cold-hardening pretreatment and without a cold-hardening pretreatment in both S and C lines (***p < .001) only) but also much lower than in both sexes when mating success was tested at 33°C (Figure 1). Similar selective differences are typically found between the sexes at benign temperature (Singh & Punzalan, 2018). In addition, this finding is consistent with the well-known hypothesis of stronger selection for mating in males than in females, as predicted from sexual selection theory (Andersson, 1994;Brooks & Endler, 2001;Darwin, 1871;Janicke, Häderer, Lajeunesse, & Anthes, 2016).…”

Cross-sex genetic correlations for fitness and fitness components: Connecting theoretical predictions to empirical patterns

“…Second, an even larger number of studies have published empirical estimates of female‐ and male‐specific selection on homologous traits that both sexes express (Cox and Calsbeek ; Morrissey ; De Lisle et al. ; Singh and Punzalan ). These data provide clear evidence of sexually antagonistic selection in cases where female and male selection gradients of a trait exhibit opposite signs ( β f β m < 0; e.g., Cox and Calsbeek ; Morrissey ; Sanjaka et al.…”

“…Equation can also be expressed as a function of sex‐specific linear selection gradients, β f and β m , which are widely estimated in animal populations (Cox and Calsbeek ; Morrissey ; De Lisle et al. ; Singh and Punzalan ). Provided the trait is genetically variable (), the criterion for becomes: where γ f and γ m represent the strengths of stabilizing selection on each sex ( and ).…”

“…Negative r fm W requires both sexually antagonistic selection (one sex below optimum and the other sex above optimum: d f d m < 0) and large displacements of each sex from its optimum relative to the amount of shared genetic variance in the trait (i.e., |d f d m | must be greater than σ 2 x /2). Equation (5) can also be expressed as a function of sex-specific linear selection gradients, β f and β m , which are widely estimated in animal populations (Cox and Calsbeek 2009;Morrissey 2016;De Lisle et al 2018;Singh and Punzalan 2018). Provided the trait is genetically variable (σ f , σ m > 0), the criterion for r fm W < 0 becomes:…”

“…A substantial number of studies have estimated additive genetic correlations between sexes for fitness components (Poissant et al 2010; Table S1), with negative correlations between the sexes taken as unambiguous signals of sexual conflict. Second, an even larger number of studies have published empirical estimates of female-and male-specific selection on homologous traits that both sexes express (Cox and Calsbeek 2009;Morrissey 2016;De Lisle et al 2018;Singh and Punzalan 2018). These data provide clear evidence of sexually antagonistic selection in cases where female and male selection gradients of a trait exhibit opposite signs (β f β m < 0; e.g., Cox and Calsbeek 2009;Morrissey 2016;Sanjaka et al 2017), or when the angle between multivariate vectors of sex-specific selection gradients is greater than orthogonal (i.e., θ > 90°; Lewis et al 2011;Gosden et al 2012;Stearns et al 2012).…”