Recently diverged taxa showing marked phenotypic and ecological diversity are optimal systems to understand the genetic processes underlying speciation. We used genome-wide markers to investigate the diversification of the Reunion grey white eye (Zosterops borbonicus) on the small volcanic island of Reunion (Mascarene archipelago), where this species complex exhibits four geographic forms that are parapatrically distributed across the island and differ strikingly in plumage colour. One form restricted to the highlands is separated by a steep ecological gradient from three distinct lowland forms which meet at narrow hybrid zones that are not associated with environmental variables. Analyses of genomic variation based on SNP data from genotyping-by-sequencing and pooled RADseq approaches, reveal that signatures of selection associated with elevation can be found at multiple regions across the genome, whereas most loci associated with the lowland forms are located on the Z sex chromosome. We identified TYRP1, a Z-linked colour gene, as a likely candidate locus underlying colour variation among lowland forms. Tests of demographic models revealed that highland and lowland forms diverged in the presence of gene flow, and divergence has progressed as gene flow was restricted by selection at loci across the genome. This system is promising to investigate how adaptation and reproductive isolation shape the genomic landscape of divergence at multiple stages of the speciation process.

中文翻译：

---

常染色体和性染色体的差异性与歌鸟谱系中很小的空间尺度上的岛内多样化有关。

最近分化的分类单元显示出明显的表型和生态多样性，是了解物种形成的遗传过程的最佳系统。我们使用全基因组标记物研究了小火山岛留尼汪岛（玛斯卡林群岛）上留尼汪岛灰白眼（Zosterops borbonicus）的多样性，该岛上的物种群表现出四种地理形态，这些地理形态分布在整个岛上，且差异很大呈羽毛色。一种限制在高地上的形式被陡峭的生态梯度与三种不同的低地形式分开，它们在狭窄的混合带相遇，而这些混合带与环境变量无关。基于SNP数据的基因组变异分析，该SNP数据来自测序基因分型和RADseq合并方法，结果表明，与海拔相关的选择标记可以在基因组的多个区域找到，而与低地形式相关的大多数基因座都位于Z性染色体上。我们确定TYRP1，Z链接的彩色基因，作为低地形式之间的颜色变化的潜在候选基因座。人口统计学模型的测试表明，高地和低地形式在存在基因流的情况下发生了分歧，并且由于基因流受到整个基因组中基因座选择的限制，分歧已经发展。该系统有望研究适应性和生殖隔离如何影响物种形成过程多个阶段的差异基因组格局。我们确定TYRP1，Z链接的彩色基因，作为低地形式之间的颜色变化的潜在候选基因座。人口统计学模型的测试表明，高地和低地形式在存在基因流的情况下发生了分歧，并且由于基因流受到整个基因组中基因座选择的限制，分歧已经发展。该系统有望研究适应性和生殖隔离如何影响物种形成过程多个阶段的差异基因组格局。我们确定TYRP1，Z链接的彩色基因，作为低地形式之间的颜色变化的潜在候选基因座。人口统计学模型的测试表明，高地和低地形式在存在基因流的情况下发生了分歧，并且由于基因流受到整个基因组中基因座选择的限制，分歧已经发展。该系统有望研究适应性和生殖隔离如何影响物种形成过程多个阶段的差异基因组格局。