Multi-locus sequence data illuminate demographic drivers of Pleistocene speciation in semi-arid southern Australian birds (Cinclosoma spp.)

Background: During the Pleistocene, shifts of species distributions and their isolation in disjunct refugia led to varied outcomes in how taxa diversified. Some species diverged, others did not. Here, we begin to address another facet of the role of the Pleistocene in generating today’s diversity. We ask which processes contributed to divergence in semi-arid southern Australian birds. We isolated 11 autosomal nuclear loci and one mitochondrial locus from a total of 29 specimens of the sister species pair, Chestnut Quail-thrush Cinclosoma castanotum and Copperback Quail-thrush C. clarum. Results: A population clustering analysis confirmed the location of the current species boundary as a well-known biogeographical barrier in southern Australia, the Eyrean Barrier. Coalescent-based analyses placed the time of species divergence to the Middle Pleistocene. Gene flow between the species since divergence has been low. The analyses suggest the effective population size of the ancestor was 54 t...

研究背景：更新世（Pleistocene）时期，物种种群分布的变迁及其在隔离避难所中的隔离，使得不同类群的演化分化产生了多样的结果——部分类群发生了物种分化，部分则未出现分化。本研究旨在探讨更新世在塑造现今生物多样性过程中所扮演角色的另一维度，旨在阐明澳大利亚南部半干旱地区鸟类类群物种分化的关键驱动过程。研究团队从姊妹物种对——棕鹑鸫（Chestnut Quail-thrush, *Cinclosoma castanotum*）与铜背鹑鸫（Copperback Quail-thrush, *C. clarum*）的总计29份标本中，成功分离得到11个常染色体核基因座（autosomal nuclear loci）与1个线粒体基因座（mitochondrial locus）。
研究结果：种群聚类分析证实，当前的物种边界恰好坐落于澳大利亚南部一处知名的生物地理屏障——艾尔屏障（Eyrean Barrier）。基于溯祖理论的分析（coalescent-based analyses）显示，物种分化的时间发生在中更新世（Middle Pleistocene）。物种分化后二者间的基因流水平较低。分析结果表明，其祖先种群的有效种群规模为54……