Am Nat. 2019 Aug;194(2):230-245. doi: 10.1086/704156. Epub 2019 Jun 14.
Polyphenisms-alternative morphs produced through plasticity-can reveal the evolutionary and ecological processes that initiate and maintain diversity within populations. We examined lifetime fitness consequences of two morphs in a polyphenic population of Arizona tiger salamanders using a 27-year data set with 1,317 adults and 6,862 captures across eight generations. Larval salamanders develop into either an aquatic paedomorph that retains larval traits and stays in its natal pond or a terrestrial metamorph that undergoes metamorphosis. To evaluate the adaptive significance of this polyphenism, we compared lifetime reproductive success of each morph and assessed how life-history strategies and spatiotemporal variation explained fitness. We found sex-specific differences in lifetime fitness between morphs. For males, paedomorphs had more reproductive opportunities than metamorphs when we accounted for the potential mating advantage of larger males. For females, in contrast, metamorphs had higher estimated egg production than paedomorphs. Life-history strategies differed between morphs largely because the morphs maximized different ends of the trade-off between age at first reproduction and longevity. Spatiotemporal variation affected larval more than adult life-history traits, with little to no effect on lifetime fitness. Thus, environmental variation likely explains differences in morph production across time and space but contributes little to lifetime fitness differences between morphs and sexes. Our long-term study and measures of lifetime fitness provide unique insight into the complex selective regimes potentially acting on each morph and sex. Our findings motivate future work to examine how sex-specific selection may contribute to the maintenance of polyphenism.
多态性——通过可塑性产生的替代形态——可以揭示引发和维持种群内多样性的进化和生态过程。我们使用 27 年的数据，对亚利桑那州虎蝾螈的一个多态种群中的两种形态的终生适应度进行了研究，该数据包括 1317 个成年个体和 6862 次捕获，跨越了 8 个世代。幼体蝾螈发育成具有幼体特征且留在其出生地池塘中的水生幼态，或经历变态的陆生变态。为了评估这种多态性的适应意义，我们比较了每种形态的终生生殖成功率，并评估了生活史策略和时空变化如何解释适应性。我们发现形态之间的终生适应性存在性别特异性差异。对于雄性，当考虑到较大雄性的潜在交配优势时，幼态个体比变态个体有更多的繁殖机会。对于雌性，相反，变态个体比幼态个体具有更高的估计产卵量。形态之间的生活史策略存在差异，主要是因为形态在初次繁殖年龄和寿命之间的权衡中最大化了不同的目标。时空变化对幼体生活史特征的影响大于对成年生活史特征的影响，对终生适应性的影响很小。因此，环境变化可能解释了形态在时间和空间上的差异，但对形态和性别之间的终生适应性差异贡献很小。我们的长期研究和终生适应性测量为潜在地作用于每种形态和性别的复杂选择机制提供了独特的见解。我们的研究结果促使未来的工作研究性别特异性选择如何有助于多态性的维持。
