Servedio Maria R, Saetre Glenn-Peter
Division of Biology 0116, University of California, San Diego, La Jolla, CA 92092-0116, USA.
Proc Biol Sci. 2003 Jul 22;270(1523):1473-9. doi: 10.1098/rspb.2003.2391.
Speciation is intimately associated with the evolution of sex-and-reproduction-related traits, including those affecting hybrid incompatibility (postzygotic isolation) and species recognition (prezygotic isolation). Genes controlling such traits are not randomly distributed in the genome but are particularly abundant on the sex chromosomes. However, the evolutionary consequences of the sex linkage of genes involved in speciation have been little explored. Here, we present simulations of a continent-island diploid model that examines the effects of reduced recombination using both autosomal and sex-linked inheritance. We show first that linkage between genes affecting postzygotic and prezygotic isolation leads to a positive feedback loop in which both are strengthened. As species recognition evolves, genes causing hybrid incompatibility will hitchhike along with those improving premating isolation, leading to stronger hybrid incompatibility and thus increased pressure for further preference divergence. Second, we show that this loop effect is generally enhanced by sex linkage, because recombination is eliminated in the heterogametic sex, leading to tighter effective linkage between the two classes of genes and because natural selection is more efficient at sex-linked loci, as recessive alleles are not masked by dominance in the heterogametic sex. Accordingly, hitchhiking can be important in promoting speciation and can also lead to increased postzygotic isolation through adaptive evolution.
物种形成与性别及繁殖相关性状的进化密切相关，这些性状包括影响杂种不亲和性（合子后隔离）和物种识别（合子前隔离）的性状。控制此类性状的基因并非随机分布在基因组中，而是在性染色体上特别丰富。然而，参与物种形成的基因的性连锁的进化后果却鲜有研究。在此，我们展示了一个大陆 - 岛屿二倍体模型的模拟，该模型使用常染色体遗传和性连锁遗传来研究重组减少的影响。我们首先表明，影响合子后隔离和合子前隔离的基因之间的连锁会导致一个正反馈循环，其中两者都会得到加强。随着物种识别的进化，导致杂种不亲和的基因将与那些改善交配前隔离的基因一起搭便车，从而导致更强的杂种不亲和性，进而增加进一步偏好分化的压力。其次，我们表明这种循环效应通常会因性连锁而增强，因为在异配性别中重组被消除，导致这两类基因之间的有效连锁更紧密，并且由于自然选择在性连锁位点更有效，因为隐性等位基因在异配性别中不会被显性掩盖。因此，搭便车在促进物种形成中可能很重要，并且还可以通过适应性进化导致合子后隔离增加。
