Data from: A comparative analysis of the mechanisms underlying speciation on Lord Howe Island

On Lord Howe Island, speciation is thought to have taken place in situ in a diverse array of distantly related plant taxa (Metrosideros, Howea and Coprosma; Proc. Natl Acad. Sci. USA 108, 2011, 13188). We now investigate whether the speciation processes were driven by divergent natural selection in each genus by examining the extent of ecological and genetic divergence. We present new and extensive, ecological and genetic data for all three genera. Consistent with ecologically driven speciation, outlier loci were detected using genome scan methods. This mechanism is supported by individual-based analyses of genotype–environment correlations within species, demonstrating that local adaptation is currently widespread on the island. Genetic analyses show that prezygotic isolating barriers within species are currently insufficiently strong to allow further population differentiation. Interspecific hybridization was found in both Howea and Coprosma, and species distribution modelling indicates that competitive exclusion may result in selection against admixed individuals. Colonization of new niches, partly fuelled by the rapid generation of new adaptive genotypes via hybridization, appears to have resulted in the adaptive radiation in Coprosma – supporting the ‘Syngameon hypothesis’.

在豪勋爵岛（Lord Howe Island）上，学界此前认为多个远缘植物类群——桃金娘属（Metrosideros）、豪椰属（Howea）与茜草树属（Coprosma）——均发生了原位物种形成，相关研究成果刊载于《美国国家科学院院刊》108卷，2011年，第13188页。本研究通过分析生态与遗传分化程度，旨在探究各属内的物种形成过程是否由趋异自然选择驱动。我们为上述三个类群提供了全新且全面的生态与遗传数据集。与生态驱动的物种形成机制相符，我们通过基因组扫描（genome scan）方法检测到了离群位点。该机制得到了种内基因型-环境相关性的个体水平分析支持，结果表明本地适应目前在该岛上广泛存在。遗传分析显示，当前种内的合子前生殖隔离屏障强度尚不足以支持进一步的种群分化。在豪椰属和茜草树属中均发现了种间杂交现象，而物种分布模型（species distribution modelling）结果表明，竞争排除（competitive exclusion）可能会对杂交个体产生选择压。新生态位的定植，部分得益于杂交事件快速产生新的适应性基因型，似乎推动了茜草树属的适应辐射（adaptive radiation），该结果为「协同物种群假说（Syngameon hypothesis）」提供了支持。