Centre d'Ecologie Fonctionnelle et Evolutive, UMR 5175 CNRS-Université de Montpellier, École Pratique des Hautes Études, Université Paul Valéry, 34293 Montpellier 5, France;
Institut de Systématique, Evolution, Biodiversité, UMR 7205 CNRS-École Pratique des Hautes Études, Muséum National d'Histoire Naturelle, Université Pierre-et-Marie-Curie, 75005 Paris, France.
Proc Natl Acad Sci U S A. 2017 Aug 1;114(31):8325-8329. doi: 10.1073/pnas.1702482114. Epub 2017 Jul 3.
Explaining the maintenance of adaptive diversity within populations is a long-standing goal in evolutionary biology, with important implications for conservation, medicine, and agriculture. Adaptation often leads to the fixation of beneficial alleles, and therefore it erodes local diversity so that understanding the coexistence of multiple adaptive phenotypes requires deciphering the ecological mechanisms that determine their respective benefits. Here, we show how antagonistic frequency-dependent selection (FDS), generated by natural and sexual selection acting on the same trait, maintains mimicry polymorphism in the toxic butterfly Positive FDS imposed by predators on mimetic signals favors the fixation of the most abundant and best-protected wing-pattern morph, thereby limiting polymorphism. However, by using mate-choice experiments, we reveal disassortative mate preferences of the different wing-pattern morphs. The resulting negative FDS on wing-pattern alleles is consistent with the excess of heterozygote genotypes at the supergene locus controlling wing-pattern variation in natural populations of The combined effect of positive and negative FDS on visual signals is sufficient to maintain a diversity of morphs displaying accurate mimicry with other local prey, although some of the forms only provide moderate protection against predators. Our findings help understand how alternative adaptive phenotypes can be maintained within populations and emphasize the need to investigate interactions between selective pressures in other cases of puzzling adaptive polymorphism.
解释种群内适应性多样性的维持是进化生物学中的一个长期目标，对保护、医学和农业都有重要意义。适应通常会导致有利等位基因的固定，因此会侵蚀局部多样性，因此理解多种适应性表型的共存需要破译决定它们各自利益的生态机制。在这里，我们展示了自然选择和性选择对同一特征的拮抗频率依赖选择（FDS）如何维持有毒蝴蝶的拟态多态性。FDS 对拟态信号的选择有利于最丰富和保护最好的翅膀图案形态的固定，从而限制了多态性。然而，通过使用配偶选择实验，我们揭示了不同翅膀图案形态的分离配偶偏好。对翅膀图案等位基因的负 FDS 与控制自然种群中翅膀图案变异的超级基因座上杂合基因型的过剩一致。控制视觉信号的正 FDS 和负 FDS 的综合作用足以维持表现出与其他本地猎物准确拟态的多种形态，尽管其中一些形态仅能为捕食者提供适度的保护。我们的研究结果有助于理解在种群内如何维持替代适应性表型，并强调需要在其他令人困惑的适应性多态性情况下研究选择性压力之间的相互作用。
