Geraldes A, Carneiro M, Delibes-Mateos M, Villafuerte R, Nachman M W, Ferrand N
CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, Campus Agrário de Vairão, 4485-661 Vairão, Portugal.
Mol Ecol. 2008 Oct;17(20):4489-99. doi: 10.1111/j.1365-294X.2008.03943.x.
The role of the Y chromosome in speciation is unclear. Hybrid zones provide natural arenas for studying speciation, as differential introgression of markers may reveal selection acting against incompatibilities. Two subspecies of the European rabbit (Oryctolagus cuniculus) form a hybrid zone in the Iberian Peninsula. Previous work on mitochondrial DNA (mtDNA), Y- and X-linked loci revealed the existence of two divergent lineages in the rabbit genome and that these lineages are largely subspecies-specific for mtDNA and two X-linked loci. Here we investigated the geographic distribution of the two Y chromosome lineages by genotyping two diagnostic single nucleotide polymorphisms in a sample of 353 male rabbits representing both subspecies, and found that Y chromosome lineages are also largely subspecies-specific. We then sequenced three autosomal loci and discovered considerable variation in levels of differentiation at these loci. Finally, we compared estimates of population differentiation between rabbit subspecies at 26 markers and found a surprising bimodal distribution of F(ST)values. The vast majority of loci showed little or no differentiation between rabbit subspecies while a few loci, including the SRY gene, showed little or no introgression across the hybrid zone. Estimates of population differentiation for the Y chromosome were surprisingly high given that there is male-biased dispersal in rabbits. Taken together, these data indicate that there is a clear dichotomy in the rabbit genome and that some loci remain highly differentiated despite extensive gene flow following secondary contact.
Y染色体在物种形成中的作用尚不清楚。杂交区为研究物种形成提供了天然场所，因为标记的差异渗入可能揭示针对不相容性的选择作用。欧洲野兔（穴兔）的两个亚种在伊比利亚半岛形成了一个杂交区。先前对线粒体DNA（mtDNA）、Y连锁和X连锁基因座的研究揭示了兔基因组中存在两个不同的谱系，并且这些谱系在很大程度上是mtDNA和两个X连锁基因座的亚种特异性。在这里，我们通过对代表两个亚种的353只雄性兔子样本中的两个诊断性单核苷酸多态性进行基因分型，研究了两个Y染色体谱系的地理分布，发现Y染色体谱系在很大程度上也是亚种特异性的。然后，我们对三个常染色体基因座进行了测序，并发现这些基因座的分化水平存在相当大的差异。最后，我们比较了兔亚种在26个标记处的种群分化估计值，发现F(ST)值呈现出惊人的双峰分布。绝大多数基因座在兔亚种之间几乎没有或没有分化，而少数基因座，包括SRY基因，在杂交区几乎没有或没有渗入。考虑到兔子存在雄性偏向的扩散，Y染色体的种群分化估计值出奇地高。综上所述，这些数据表明兔基因组中存在明显的二分法，并且尽管二次接触后有广泛的基因流动，但一些基因座仍然高度分化。
