Ross-Ibarra Jeffrey, Tenaillon Maud, Gaut Brandon S
Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA.
Genetics. 2009 Apr;181(4):1399-413. doi: 10.1534/genetics.108.097238. Epub 2009 Jan 19.
Gene flow plays a fundamental role in plant evolutionary history, yet its role in population divergence--and ultimately speciation--remains poorly understood. We investigated gene flow and the modalities of divergence in the domesticated Zea mays ssp. mays and three wild Zea taxa using sequence polymorphism data from 26 nuclear loci. We described diversity across loci and assessed evidence for adaptive and purifying selection at nonsynonymous sites. For each of three divergence events in the history of these taxa, we used approximate Bayesian simulation to estimate population sizes and divergence times and explicitly compare among alternative models of divergence. Our estimates of divergence times are surprisingly consistent with previous data from other markers and suggest rapid diversification of lineages within Zea in the last approximately 150,000 years. We found widespread evidence of historical gene flow, including evidence for divergence in the face of gene flow. We speculate that cultivated maize may serve as a bridge for gene flow among otherwise allopatric wild taxa.
基因流在植物进化史上起着基础性作用，然而其在种群分化——最终到物种形成——过程中的作用仍知之甚少。我们利用来自26个核基因座的序列多态性数据，研究了驯化的玉米（Zea mays ssp. mays）和三个野生玉米类群中的基因流及分化模式。我们描述了各基因座的多样性，并评估了非同义位点上适应性选择和纯化选择的证据。对于这些类群历史上的三次分化事件，我们使用近似贝叶斯模拟来估计种群大小和分化时间，并明确比较不同的分化模型。我们对分化时间的估计出人意料地与先前来自其他标记的数据一致，并表明在过去约15万年里玉米属内各谱系迅速分化。我们发现了广泛的历史基因流证据，包括在基因流存在的情况下发生分化的证据。我们推测，栽培玉米可能成为原本异域分布的野生类群之间基因流的桥梁。
