Data from: Asymmetric introgression in a spotted salamander hybrid zone

Before the establishment of reproductive isolation, deeply diverged
intraspecific lineages can experience complex genetic and behavioral
interactions as they come into secondary contact. Divergent selective and
demographic processes mediate gene flow among lineages, resulting in
hybrid zones with complex biogeographic structure. Discordance in the
biogeographic patterns of autosomal and maternally inherited loci provides
a useful window to infer the processes mediating admixture and
introgression across hybrid zones. Here, we sampled 489 genotypes across a
hybrid zone between 2 phylogeographic lineages of the spotted salamander,
Ambystoma maculatum, and characterize discordant patterns of nuclear and
mitochondrial introgression across the contact boundary. Our results
indicate asymmetric introgression of nuclear DNA beyond the contact
boundary from the western to eastern lineage, with introgression of
eastern mitochondrial DNA into the western lineage. We discuss alternative
mechanisms for this pattern and attribute this result to neutral patterns
of population expansion of the western lineage into the east in
combination with female mate choice for larger-bodied western males. Our
results underscore the complexity of interacting mechanisms that give rise
to reproductive asymmetries in the earliest stages of the speciation
process.

在生殖隔离形成之前，深度分化的种内谱系在二次接触时会发生复杂的遗传与行为相互作用。分化选择与种群统计过程调控着谱系间的基因流，形成具有复杂生物地理结构的杂交区。常染色体与母系遗传位点在生物地理模式上的不一致性，为推断杂交区内调控混合与基因渗入的过程提供了有效视角。本研究在斑点蝾螈（Ambystoma maculatum）两个系统地理谱系的杂交区内采集了489个基因型样本，分析了接触边界处核基因与线粒体基因渗入的不一致模式。结果显示，核DNA从西部谱系向东部谱系跨越接触边界发生不对称渗入，而东部线粒体DNA则渗入西部谱系。我们探讨了该模式的潜在机制，并将此结果归因于西部谱系向东部的中性种群扩张模式，以及雌性对体型较大的西部雄性的配偶选择。研究结果凸显了在物种形成早期阶段，导致生殖不对称性的相互作用机制的复杂性。