Estimation of isolation times of the island species in the Drosophila simulans complex from multilocus DNA sequence data.
Estimation of isolation times of the island species in the Drosophila simulans complex from multilocus DNA sequence data.
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DOI：
10.1371/journal.pone.0002442
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发表时间：
2008-06-18
期刊：
影响因子：
3.7
通讯作者：
Kliman RM
中科院分区：
文献类型：
--
作者：
McDermott SR;Kliman RM
拟果蝇物种复合体一直是研究新物种形成的重要模型系统。该综合体由世界性物种D. simulans和两个岛屿特有物种D. mauritiana和D. sechellia组成。大量的努力已经投入到重建这个复合体的自然历史上，部分是为了推断物种之间的功能差异产生的背景。在这方面，需要估计的一个关键参数是每个岛屿物种的初始隔离时间(t)。低重组区域的基因座在复合体内的分化程度低于其他基因座，但两类的分化程度相似。这可能反映了低重组位点在初始分离后的基因流动，但也可能反映了低重组位点在基因搭便车或假搭便车时，群体大小变化对两类重组位点的差异效应。新的17个位点的DNA序列变异数据证实了先前13个位点的观察结果，即低重组基因的DNA序列差异减小。提出了两个模型来估计t和其他相关参数（导致岛屿物种的谱系的替代率校正因子，以及在4参数模型的情况下，祖先与现存有效群体大小的比率）从多位点DNA序列数据。总的来说，这两个岛屿物种似乎是在大约同一时间分离出来的，这里估计是在25万年前。此外，低重组区和高重组区基因分化模式的差异似乎可以通过允许祖先群体比现存拟南猿群体稍大的有效群体规模来调和。
The Drosophila simulans species complex continues to serve as an important model system for the study of new species formation. The complex is comprised of the cosmopolitan species, D. simulans, and two island endemics, D. mauritiana and D. sechellia. A substantial amount of effort has gone into reconstructing the natural history of the complex, in part to infer the context in which functional divergence among the species has arisen. In this regard, a key parameter to be estimated is the initial isolation time (t) of each island species. Loci in regions of low recombination have lower divergence within the complex than do other loci, yet divergence from D. melanogaster is similar for both classes. This might reflect gene flow of the low-recombination loci subsequent to initial isolation, but it might also reflect differential effects of changing population size on the two recombination classes of loci when the low-recombination loci are subject to genetic hitchhiking or pseudohitchhiking New DNA sequence variation data for 17 loci corroborate the prior observation from 13 loci that DNA sequence divergence is reduced in genes of low recombination. Two models are presented to estimate t and other relevant parameters (substitution rate correction factors in lineages leading to the island species and, in the case of the 4-parameter model, the ratio of ancestral to extant effective population size) from the multilocus DNA sequence data. In general, it appears that both island species were isolated at about the same time, here estimated at ∼250,000 years ago. It also appears that the difference in divergence patterns of genes in regions of low and higher recombination can be reconciled by allowing a modestly larger effective population size for the ancestral population than for extant D. simulans.
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