Wang R-X, Zhao Y-L
BC Cancer Research Centre, BC Cancer Agency, Vancouver, British Columbia, Canada.
Heredity (Edinb). 2008 Mar;100(3):326-36. doi: 10.1038/sj.hdy.6801081. Epub 2007 Dec 19.
In animals, hybrid sterility and inviability between closely related species often affect only the heterogametic sex (XY). This widespread phenomenon, known as Haldane's rule, is an early speciation event found across broad taxa, but the role of heterogametic hybrid incompatibilities, as opposed to homogametic ones, as a barrier in a speciation process remains obscure. It has been hypothesized that heterogametic incompatibility may be a more efficient mechanism in driving speciation. The population dynamics after (rather than before) the occurrence of sex-biased incompatibilities may account for Haldane's rule. In this study, a recursion model of hybrid zones was developed to investigate the differences between heterogametic and homogametic incompatibilities. The selection strengths and selection patterns of sex chromosome-linked, two-locus Bateson-Dobzhansky-Muller (BDM) genetic incompatibilities were examined. It is noted that a sex-biased hybrid incompatibility in a hybrid zone confers asymmetric and uneven impedance to gene flow. The clines of different loci in such a hybrid zone displayed diverse differentiation in their width, steepness and asymmetry. Alleles involved in the incompatibility face much stronger resistance to cross a hybrid zone. Different sex-biased BDM incompatibilities also affect the flow of neutral alleles differently. Compared to a homogametic one, heterogametic incompatibility is a weaker but more asymmetric barrier. These unique patterns of gene flow may explain uneven divergence among different genomic regions during speciation between some closely related species.
在动物中，亲缘关系相近的物种之间的杂种不育和 inviability 通常只影响异配性别（XY）。这种普遍现象被称为霍尔丹法则，是在广泛的分类群中发现的早期物种形成事件，但与同配杂种不相容性相比，异配杂种不相容性在物种形成过程中作为一种障碍的作用仍不清楚。有人推测，异配不相容性可能是推动物种形成的一种更有效的机制。性别偏向不相容性出现后（而非之前）的种群动态可能解释了霍尔丹法则。在本研究中，开发了一个杂交带递归模型来研究异配和同配不相容性之间的差异。研究了性染色体连锁的双位点贝茨森 - 多布赞斯基 - 穆勒（BDM）遗传不相容性的选择强度和选择模式。值得注意的是，杂交带中的性别偏向杂种不相容性对基因流赋予了不对称且不均匀的阻抗。在这样一个杂交带中，不同位点的渐变群在宽度、陡峭度和不对称性方面表现出不同的分化。参与不相容性的等位基因在跨越杂交带时面临更强的阻力。不同的性别偏向 BDM 不相容性对中性等位基因流的影响也不同。与同配不相容性相比，异配不相容性是一个较弱但更不对称的障碍。这些独特的基因流模式可能解释了一些亲缘关系相近的物种在物种形成过程中不同基因组区域之间不均匀的分化。
