Department of Biology, Duke University, Durham, North Carolina 27708, USA.
Evolution. 2012 Feb;66(2):469-85. doi: 10.1111/j.1558-5646.2011.01452.x. Epub 2011 Oct 5.
Character displacement, which arises when species diverge in sympatry to decrease competition for resources or reproductive interference, has been observed in a wide variety of plants and animals. A classic example of reproductive character displacement, presumed to be caused by reinforcing selection, is flower-color variation in the native Texas wildflower Phlox drummondii. Here, we use population genetic analyses to investigate molecular signatures of selection on flower-color variation in this species. First, we quantify patterns of neutral genetic variation across the range of P. drummondii to demonstrate that restricted gene flow and genetic drift cannot explain the pattern of flower-color divergence in this species. There is evidence of extensive gene flow across populations with different flower colors, suggesting selection caused flower-color divergence. Second, analysis of sequence variation in the genes underlying this divergence reveals a signature of a selective sweep in one of the two genes, further indicating selection is responsible for divergence in sympatry. The lack of a signature of selection at the second locus does not necessarily indicate a lack of selection on this locus but instead brings attention to the uncertainty in depending on molecular signatures to identify selection.
当物种在同域中发生分歧以减少对资源的竞争或生殖干扰时，就会出现特征替代，这种现象在各种植物和动物中都有观察到。生殖特征替代的一个经典例子，据推测是由强化选择引起的，是原产于德克萨斯州的野花 Phlox drummondii 的花颜色变化。在这里，我们使用群体遗传分析来研究该物种花颜色变化的选择的分子特征。首先，我们量化了 P. drummondii 分布范围内中性遗传变异的模式，以证明限制基因流和遗传漂变不能解释该物种花颜色分歧的模式。有证据表明，具有不同花颜色的种群之间存在广泛的基因流，表明选择导致了花颜色的分歧。其次，对导致这种分歧的基因序列变异的分析揭示了其中一个基因的选择清扫的特征，进一步表明选择是同域分歧的原因。第二个基因座没有选择的特征并不一定表明该基因座上没有选择，而是引起了对依赖分子特征来识别选择的不确定性。
