Evolutionary Biology Group, Faculty of Biology, Adam Mickiewicz University, Poznań, Poland.
Department of Medicine, Section of Genetic Medicine, University of Chicago, Chicago, Illinois, United States.
Evolution. 2023 Jun 1;77(6):1289-1302. doi: 10.1093/evolut/qpad039.
Sexual selection and sexual antagonism are important drivers of eco-evolutionary processes. The evolution of traits shaped by these processes depends on their genetic architecture, which remains poorly studied. Here, implementing a quantitative genetics approach using diallel crosses of the bulb mite, Rhizoglyphus robini, we investigated the genetic variance that underlies a sexually selected weapon that is dimorphic among males and female fecundity. Previous studies indicated that a negative genetic correlation between these two traits likely exists. We found male morph showed considerable additive genetic variance, which is unlikely to be explained solely by mutation-selection balance, indicating the likely presence of large-effect loci. However, a significant magnitude of inbreeding depression also indicates that morph expression is likely to be condition-dependent to some degree and that deleterious recessives can simultaneously contribute to morph expression. Female fecundity also showed a high degree of inbreeding depression, but the variance in female fecundity was mostly explained by epistatic effects, with very little contribution from additive effects. We found no significant genetic correlation, nor any evidence for dominance reversal, between male morph and female fecundity. The complex genetic architecture underlying male morph and female fecundity in this system has important implications for our understanding of the evolutionary interplay between purifying selection and sexually antagonistic selection.
性选择和性拮抗是生态进化过程的重要驱动因素。这些过程所塑造的特征的进化取决于它们的遗传结构，但对其的研究还很不完善。在这里，我们利用球果花螨的双列杂交实施了一种数量遗传学方法，研究了雄性形态和雌性繁殖力这两个性别选择武器的遗传方差，其中雄性形态在雄性中存在二态性，而雌性繁殖力则不存在二态性。之前的研究表明，这两个特征之间可能存在负遗传相关。我们发现雄性形态表现出相当大的加性遗传方差，这不太可能仅仅是由突变-选择平衡所解释的，这表明可能存在大效应基因座。然而，相当大的近交衰退程度也表明形态表达在某种程度上可能是条件依赖的，并且有害的隐性基因可能同时有助于形态表达。雌性繁殖力也表现出高度的近交衰退，但雌性繁殖力的方差主要由上位效应解释，加性效应的贡献很小。我们没有发现雄性形态和雌性繁殖力之间存在显著的遗传相关，也没有证据表明存在显性逆转。在这个系统中，雄性形态和雌性繁殖力的复杂遗传结构对我们理解净化选择和性拮抗选择之间的进化相互作用具有重要意义。
