Data from: Bounds to parapatric speciation: A dobzhansky-muller incompatibility model involving autosomes, X chromosomes and mitochondria

We investigate the conditions for the origin and maintenance of postzygotic isolation barriers, so called (Bateson-)Dobzhansky-Muller incompatibilities or DMIs, among populations that are connected by gene flow. Specifically, we compare the relative stability of pairwise DMIs among autosomes, X chromosomes, and mitochondrial genes. In an analytical approach based on a continent-island framework, we determine how the maximum permissible migration rates depend on the genomic architecture of the DMI, on sex bias in migration rates, and on sex-dependence of allelic and epistatic effects, such as dosage compensation. Our results show that X-linkage of DMIs can enlarge the migration bounds relative to autosomal DMIs or autosome-mitochondrial DMIs, in particular in the presence of dosage compensation. The effect is further strengthened with male-biased migration. This mechanism might contribute to a higher density of DMIs on the X chromosome (large X-effect) that has been observed in several species clades. Furthermore, our results agree with empirical findings of higher introgression rates of autosomal compared to X-linked loci.

本研究探讨了存在基因流（gene flow）连通的种群间，合子后生殖隔离屏障（postzygotic isolation barriers）的起源与维持条件，这类屏障即所谓（贝特松-）多布然斯基-马勒不相容性（(Bateson-)Dobzhansky-Muller incompatibilities，简称DMIs）。具体而言，我们比较了常染色体（autosomes）、X染色体（X chromosomes）与线粒体基因（mitochondrial genes）上成对DMIs的相对稳定性。本研究采用基于大陆-岛屿模型（continent-island framework）的解析方法（analytical approach），分析了最大允许迁移速率如何取决于DMIs的基因组结构（genomic architecture）、迁移速率的性别偏倚（sex bias），以及等位基因与上位性效应的性别依赖性，例如剂量补偿效应（dosage compensation）。研究结果表明，相较于常染色体DMIs或常染色体-线粒体DMIs，DMIs的X连锁（X-linkage）可扩大允许的迁移范围，尤其在存在剂量补偿效应的情况下；雄性偏倚迁移（male-biased migration）会进一步增强这一效应。该机制或有助于解释多个物种支系（species clades）中已观测到的X染色体上DMIs密度更高的现象（即大X效应（large X-effect））。此外，本研究结果与实证发现一致：相较于X连锁基因座（loci），常染色体基因座具有更高的渐渗速率（introgression rates）。