Connallon Tim, Matthews Genevieve
School of Biological Sciences, and Centre for Geometric Biology Monash University Clayton Victoria 3800 Australia.
Evol Lett. 2019 Apr 29;3(3):254-262. doi: 10.1002/evl3.116. eCollection 2019 Jun.
Sex differences in morphology, physiology, development, and behavior are widespread, yet the sexes inherit nearly identical genomes, causing most traits to exhibit strong and positive cross-sex genetic correlations. In contrast to most other traits, estimates of cross-sex genetic correlations for fitness and fitness components ( ) are generally low and occasionally negative, implying that a substantial fraction of standing genetic variation for fitness might be sexually antagonistic (i.e., alleles benefitting one sex harm the other). Nevertheless, while low values of are often regarded as consequences of sexually antagonistic selection, it remains unclear exactly how selection and variation in quantitative traits interact to determine the sign and magnitude of , making it difficult to relate empirical estimates of cross-sex genetic correlations to the evolutionary processes that might shape them. We present simple univariate and multivariate quantitative genetic models that explicitly link patterns of sex-specific selection and trait genetic variation to the cross-sex genetic correlation for fitness. We show that provides an unreliable signal of sexually antagonistic selection for two reasons. First, is constrained to be less than the cross-sex genetic correlation for traits affecting fitness, regardless of the nature of selection on the traits. Second, sexually antagonistic selection is an insufficient condition for generating negative cross-sex genetic correlations for fitness. Instead, negative fitness correlations between the sexes ( can only emerge when selection is sexually antagonistic the strength of directional selection on each sex is strong relative to the amount of shared additive genetic variation in female and male traits. These results imply that empirical tests of sexual antagonism that are based on estimates of will be conservative and underestimate its true scope. In light of these theoretical results, we revisit current data on and sex-specific selection and find that they are consistent with the theory.
形态、生理、发育和行为方面的性别差异广泛存在，然而两性继承的基因组几乎相同，这使得大多数性状呈现出强烈且正向的跨性别遗传相关性。与大多数其他性状不同，对适合度及其组成部分（ ）的跨性别遗传相关性估计通常较低，偶尔甚至为负，这意味着适合度的大量现有遗传变异可能具有性拮抗作用（即有利于某一性别的等位基因会对另一性别造成损害）。尽管如此，虽然 的低值通常被视为性拮抗选择的结果，但尚不清楚数量性状的选择和变异究竟如何相互作用来决定 的符号和大小，这使得难以将跨性别遗传相关性的实证估计与可能塑造它们的进化过程联系起来。我们提出了简单的单变量和多变量数量遗传模型，明确地将性别特异性选择模式和性状遗传变异与适合度的跨性别遗传相关性联系起来。我们表明， 为性拮抗选择提供了不可靠的信号，原因有二。首先，无论性状的选择性质如何， 都被限制为小于影响适合度的性状的跨性别遗传相关性。其次，性拮抗选择并非产生适合度负向跨性别遗传相关性的充分条件。相反，两性之间的负适合度相关性（ ）只有在选择具有性拮抗作用且相对于雌性和雄性性状中共享的加性遗传变异量，对每一性别的定向选择强度很强时才会出现。这些结果意味着基于 估计的性拮抗实证检验将较为保守，并低估其真实范围。鉴于这些理论结果，我们重新审视了当前关于 和性别特异性选择的数据，发现它们与该理论一致。
