Maintenance of species differences in closely related tetraploid parasitic Euphrasia (Orobanchaceae) on an isolated island
Maintenance of species differences in closely related tetraploid parasitic Euphrasia (Orobanchaceae) on an isolated island
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孤岛上密切相关的四倍体寄生大戟科（Orobanchaceae）物种差异的维持
DOI：
10.1101/2020.04.29.067579
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Becher H
中科院分区：
文献类型：
--
作者：
Becher H
多倍性在被子植物进化中普遍存在，在适应和物种形成中起着重要作用。然而，由于复杂的序列同源性，具有挑战性的基因组组装和分类学的复杂性，多倍体群体研究不足。在这里，我们研究适应性分歧在分类学上复杂的eyebrights（Euphrasia），最近的分歧，表型可塑性和杂交模糊种的界限。我们专注于三个密切相关的四倍体物种与对比的生态偏好，是同域的公平岛，在不列颠群岛的一个小孤岛。使用一个共同的花园实验，我们表现出遗传成分的形态差异，这些物种之间存在。使用全基因组测序和一种新的k-mer方法，我们称之为“Tetmer”，我们证明，该物种是异源多倍体的起源，与亚基因组分歧约5%。使用1200万个SNP，我们显示了跨物种的亚基因组同源性，最近物种形成的序列差异非常低。这种遗传变异是广泛的物种结构，与公平岛石楠和Euphrasia micrantha的明显分歧，而草地Euphrasia arctica和coastalEuphrasia foulaensis更密切相关。总的来说，我们表明，tetraploidEuphrasiais系统的异源多倍体的冰后期物种分歧，适应新的环境可能会赋予旧的变种重新排列成新的遗传谱系。
Polyploidy is pervasive in angiosperm evolution and plays important roles in adaptation and speciation. However, polyploid groups are understudied due to complex sequence homology, challenging genome assembly, and taxonomic complexity. Here, we study adaptive divergence in taxonomically complex eyebrights (Euphrasia), where recent divergence, phenotypic plasticity, and hybridization blur species boundaries. We focus on three closely related tetraploid species with contrasting ecological preferences that are sympatric on Fair Isle, a small isolated island in the British Isles. Using a common garden experiment, we show a genetic component to the morphological differences present between these species. Using whole-genome sequencing and a novel k-mer approach we call "Tetmer", we demonstrate that the species are of allopolyploid origin, with a sub-genome divergence of approximately 5%. Using ∼2 million SNPs, we show sub-genome homology across species, with a very low sequence divergence characteristic of recent speciation. This genetic variation is broadly structured by species, with clear divergence of Fair Isle heathlandEuphrasia micrantha, while grasslandEuphrasia arcticaand coastalEuphrasia foulaensisare more closely related. Overall, we show that tetraploidEuphrasiais a system of allopolyploids of postglacial species divergence, where adaptation to novel environments may be conferred by old variants rearranged into new genetic lineages.