Department of Biological Sciences, Vanderbilt University, Box 351634 Station B, Nashville, TN 37235, USA.
Mol Ecol. 2011 Nov;20(22):4671-82. doi: 10.1111/j.1365-294X.2011.05311.x. Epub 2011 Oct 14.
This study tests how divergent natural selection promotes genomic differentiation during ecological speciation. Specifically, we use adaptive ecological divergence (here, population divergence in host plant use and preference) as a proxy for selection strength and evaluate the correlation between levels of adaptive and genetic differentiation across pairwise population comparisons. Positive correlations would reveal the pattern predicted by our hypothesis, that of 'isolation by adaptation' (IBA). Notably, IBA is predicted not only for selected loci but also for neutral loci. This may reflect the effects of divergent selection on neutral loci that are 'loosely linked' to divergently selected loci or on geneflow restriction that facilitates genetic drift at all loci, including neutral loci that are completely unlinked to those evolving under divergent selection. Here, we evaluate IBA in maple- and willow-associated populations of Neochlamisus bebbianae leaf beetles. To do so, we collected host preference data to construct adaptive divergence indices and used AFLPs (amplified fragment length polymorphisms) and mitochondrial sequences to quantify genetic differentiation. Partial Mantel tests showed significant IBA in 'pooled' analyses of putatively neutral and of putatively selected ('outlier') AFLP loci. This pattern was also recovered in 12% of 'locus-specific' analyses that separately evaluated genetic differentiation at individual neutral loci. These results provided evidence for widespread effects of selection on neutral genomic divergence. Our collective findings indicate that host-related selection may play important roles in the population genomic differentiation of both neutral and selected gene regions in herbivorous insects.
本研究检验了发散性自然选择在生态物种形成过程中如何促进基因组分化。具体来说，我们将适应性生态分歧（这里是指在宿主植物利用和偏好方面的种群分歧）作为选择强度的代理，并评估了在成对种群比较中适应性和遗传分化水平之间的相关性。正相关将揭示我们假设的模式，即“适应隔离”（IBA）。值得注意的是，IBA 不仅预测了选择的基因座，而且预测了中性基因座。这可能反映了分歧选择对与分歧选择基因座“松散连锁”的中性基因座或对基因流限制的影响，基因流限制促进了所有基因座的遗传漂变，包括与受分歧选择进化的基因座完全不连锁的中性基因座。在这里，我们评估了 Neochlamisus bebbianae 叶甲与枫杨相关的种群中 IBA。为此，我们收集了宿主偏好数据来构建适应性分歧指数，并使用 AFLP（扩增片段长度多态性）和线粒体序列来量化遗传分化。部分 Mantel 检验显示，在假定中性和假定选择（“异常值”）AFLP 基因座的“汇总”分析中存在显著的 IBA。这种模式也在 12%的“特定基因座”分析中得到了恢复，这些分析分别评估了单个中性基因座的遗传分化。这些结果为选择对中性基因组分歧的广泛影响提供了证据。我们的综合研究结果表明，宿主相关的选择可能在植食性昆虫的中性和选择基因区域的种群基因组分化中发挥重要作用。
