Introgression between non-sister species of honeyeaters (Aves: Meliphagidae) several million years after speciation

We reassessed whether two parapatric non-sister Australian honeyeater species (Aves: Meliphagidae), varied and mangrove honeyeaters (Gavicalis versicolor and G. fasciogularis, respectively), that diverged from a common ancestor c. 2.5 Mya intergrade in the Townsville area of north-eastern Queensland. Consistent with a previous specimenbased study, by using genomics methods we show one-way gene flow for autosomal but not Z-linked markers from varied into mangrove honeyeaters. Introgression barely extends south of the area of parapatry in and around the city of Townsville. While demonstrating the long-term porosity of species boundaries over several million years, our data also suggest a clear role of sex chromosomes in maintaining reproductive isolation.

本研究重新评估了两种约250万年前从共同祖先分化而来的、邻域分布（parapatric）且非姐妹类群的澳大利亚吸蜜鸟（鸟纲：吸蜜鸟科（Meliphagidae））——杂色吸蜜鸟（Gavicalis versicolor）与红树林吸蜜鸟（Gavicalis fasciogularis，二者分别对应）——是否在澳大利亚昆士兰州东北部的汤斯维尔地区存在渐变杂交。与此前一项基于标本的研究结果一致，本研究通过基因组学方法证实，常染色体标记存在从杂色吸蜜鸟向红树林吸蜜鸟的单向基因流，而Z连锁标记（Z-linked markers）则未表现出该现象。基因渐渗（introgression）的分布范围几乎未超出汤斯维尔市及周边邻域分布区以南区域。本研究结果既证实了物种边界在数百万年的时间尺度下仍具有长期可渗透性，同时也表明性染色体在维持生殖隔离（reproductive isolation）方面发挥了明确作用。