Wessinger Carolyn A, Kelly John K
Am Nat. 2018 May;191(5):582-594. doi: 10.1086/696856. Epub 2018 Mar 14.
Pollinator-mediated selection on plants can favor transitions to a new pollinator depending on the relative abundances and efficiencies of pollinators present in the community. A frequently observed example is the transition from bee pollination to hummingbird pollination. We present a population genetic model that examines whether the ability to inbreed can influence evolutionary change in traits that underlie pollinator attraction. We find that a transition to a more efficient but less abundant pollinator is favored under a broadened set of ecological conditions if plants are capable of delayed selfing rather than obligately outcrossing. Delayed selfing allows plants carrying an allele that attracts the novel pollinator to reproduce even when this pollinator is rare, providing reproductive assurance. In addition, delayed selfing weakens the effects of Haldane's sieve by increasing the fixation probability for recessive alleles that confer adaptation to the new pollinator. Our model provides novel insight into the paradoxical abundance of recessive mutations in adaptation to hummingbird attraction. It further predicts that transitions to efficient but less abundant pollinators (such as hummingbirds in certain communities) should disproportionately occur in self-compatible lineages. Currently available mating system data sets are consistent with this prediction, and we suggest future areas of research that will enable a rigorous test of this theory.
传粉者介导的对植物的选择可能有利于向新传粉者的转变，这取决于群落中现存传粉者的相对丰度和效率。一个经常观察到的例子是从蜜蜂传粉向蜂鸟传粉的转变。我们提出了一个种群遗传模型，该模型研究近亲繁殖的能力是否会影响传粉者吸引力所依赖的性状的进化变化。我们发现，如果植物能够延迟自花授粉而不是专性异花授粉，那么在更广泛的生态条件下，向更高效但数量更少的传粉者的转变是有利的。延迟自花授粉使携带吸引新传粉者等位基因的植物即使在这种传粉者稀少时也能繁殖，从而提供繁殖保障。此外，延迟自花授粉通过增加赋予对新传粉者适应性的隐性等位基因的固定概率，削弱了霍尔丹筛的影响。我们的模型为适应蜂鸟吸引力的隐性突变的反常丰度提供了新的见解。它进一步预测，向高效但数量更少的传粉者（如某些群落中的蜂鸟）的转变应该在自交亲和的谱系中不成比例地发生。目前可用的交配系统数据集与这一预测一致，我们建议了未来的研究领域，以便能够对这一理论进行严格检验。
