Tipping the Scales: The Migration–Selection Balance Leans toward Selection in Snake Venoms
Tipping the Scales: The Migration–Selection Balance Leans toward Selection in Snake Venoms
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倾斜天平：迁移——选择平衡倾向于蛇毒的选择
DOI：
10.1093/molbev/msy207
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发表时间：
2018
影响因子：
10.7
通讯作者：
Wray, Gregory
中科院分区：
文献类型：
--
作者：
Margres, Mark J;Patton, Austin;Wray, Kenneth P;Hassinger, Alyssa T;Ward, Micaiah J;Lemmon, Emily Moriarty;Lemmon, Alan R;Rokyta, Darin R;Wray, Gregory
迁移-选择相互作用是有益等位基因在群体中频率是否增加的最强决定因素。然而，检验基因流在适应性环境中的作用的实证研究结果在很大程度上是模棱两可的，相反结果的例子被反复记录（例如，高水平基因流的局部适应与基因淹没）。我们比较了具有不同生态的三种同域毒蛇的中性基因组和毒液表达差异，以确定迁移-选择不平衡是否以及如何导致局部适应。我们专门测试了中性分化是否可以在距离隔离框架内预测表型分化。中性和表型分化的解耦表明选择导致了适应性分歧，而与迁移无关，而中性和毒液表达分化之间的显着关系将为支持基因流的约束力提供证据。中性分化和地理距离仅预测通才物种的表型分化，表明选择是两种专才物种适应性毒液进化的迁移-选择平衡的主要机制。人们认为分散对遗传分化的影响比专门化的影响更大，但我们的结果表明相反。更大的专业化可能会导致更大的多样化率，而选择压力的极端空间和时间变化可能有利于在强稳定选择下进化的通才表型。我们的结果与这些预期一致，这表明在适应性环境中检查基因流的作用的研究的模棱两可的结果可以用生态专业化理论来解释。
The migration–selection interaction is the strongest determinant of whether a beneficial allele increases in frequency within a population. Results of empirical studies examining the role of gene flow in an adaptive context, however, have largely been equivocal, with examples of opposing outcomes being repeatedly documented (e.g., local adaptation with high levels of gene flow vs. gene swamping). We compared neutral genomic and venom expression divergence for three sympatric pit vipers with differing ecologies to determine if and how migration–selection disequilibria result in local adaptation. We specifically tested whether neutral differentiation predicted phenotypic differentiation within an isolation-by-distance framework. The decoupling of neutral and phenotypic differentiation would indicate selection led to adaptive divergence irrespective of migration, whereas a significant relationship between neutral and venom expression differentiation would provide evidence in favor of the constraining force of gene flow. Neutral differentiation and geographic distance predicted phenotypic differentiation only in the generalist species, indicating that selection was the predominant mechanism in the migration–selection balance underlying adaptive venom evolution in both specialists. Dispersal is thought to be a stronger influence on genetic differentiation than specialization, but our results suggest the opposite. Greater specialization may lead to greater diversification rates, and extreme spatial and temporal variation in selective pressures can favor generalist phenotypes evolving under strong stabilizing selection. Our results are consistent with these expectations, suggesting that the equivocal findings of studies examining the role of gene flow in an adaptive context may be explained by ecological specialization theory.