Kralj-Fišer Simona, Kuntner Matjaž, Debes Paul Vincent
ZRC SAZU, Institute of Biology, Ljubljana, Slovenia.
Faculty of Mathematics, Natural Sciences and Information Technologies, University of Primorska, Koper, Slovenia.
J Evol Biol. 2023 Oct;36(10):1428-1437. doi: 10.1111/jeb.14217. Epub 2023 Sep 13.
Sexual dimorphism, or sex-specific trait expression, may evolve when selection favours different optima for the same trait between sexes, that is, under antagonistic selection. Intra-locus sexual conflict exists when the sexually dimorphic trait under antagonistic selection is based on genes shared between sexes. A common assumption is that the presence of sexual-size dimorphism (SSD) indicates that sexual conflict has been, at least partly, resolved via decoupling of the trait architecture between sexes. However, whether and how decoupling of the trait architecture between sexes has been realized often remains unknown. We tested for differences in architecture of adult body size between sexes in a species with extreme SSD, the African hermit spider (Nephilingis cruentata), where adult female body size greatly exceeds that of males. Specifically, we estimated the sex-specific importance of genetic and maternal effects on adult body size among individuals that we laboratory-reared for up to eight generations. Quantitative genetic model estimates indicated that size variation in females is to a larger extent explained by direct genetic effects than by maternal effects, but in males to a larger extent by maternal than by genetic effects. We conclude that this sex-specific body-size architecture enables body-size evolution to proceed much more independently than under a common architecture to both sexes.
性二态性，即特定性别的性状表达，当选择有利于两性对同一性状的不同最优值时，也就是在对抗性选择下，可能会进化。当对抗性选择下的性二态性状基于两性共享的基因时，就存在基因座内的性冲突。一个常见的假设是，性大小二态性（SSD）的存在表明性冲突至少部分是通过两性性状结构的解耦来解决的。然而，两性性状结构的解耦是否以及如何实现往往仍然未知。我们在一种具有极端SSD的物种——非洲隐居蜘蛛（Nephilingis cruentata）中测试了两性成年体型结构的差异，该物种成年雌性体型大大超过雄性。具体来说，我们估计了在实验室饲养长达八代的个体中，遗传效应和母体效应对成年体型的性别特异性重要性。数量遗传模型估计表明，雌性的体型变异在更大程度上是由直接遗传效应而非母体效应解释的，而雄性的体型变异在更大程度上是由母体效应而非遗传效应解释的。我们得出结论，这种性别特异性的体型结构使体型进化能够比在两性共有结构下更加独立地进行。
