Data from: The ‘male escape hypothesis’: sex-biased metamorphosis in response to climatic drivers in a facultatively paedomorphic amphibian

Paedomorphosis is a major evolutionary process that bypasses metamorphosis and allows reproduction in larvae. In newts and salamanders, it can be facultative with paedomorphs retaining gills and metamorphs dispersing. The evolution of these developmental processes is thought to have been driven by the costs and benefits of inhabiting aquatic versus terrestrial habitats. In this context, we aimed at testing the hypothesis that climatic drivers affect phenotypic transition and the difference across sexes because sex-ratio is biased in natural populations. Through a replicated laboratory experiment, we showed that paedomorphic palmate newts (Lissotriton helveticus) metamorphosed at a higher frequency when water availability decreased and metamorphosed earlier when temperature increased in these conditions. All responses were sex-biased, and males were more prone to change phenotype than females. Our work shows how climatic variables can affect facultative paedomorphosis and support theoretical models predicting life on land instead of in water. Moreover, because males metamorphose and leave water more often and earlier than females, these results, for the first time, give an experimental explanation for the rarity of male paedomorphosis (the ‘male escape hypothesis’) and suggest the importance of sex in the evolution of paedomorphosis versus metamorphosis.幼态延续（paedomorphosis）是一类关键的演化进程，可跳过变态发育环节，使幼虫阶段即可实现繁殖。在真螈（newts）与蝾螈（salamanders）中，该现象可呈兼性形式：幼态延续个体保留鳃部结构，而完成变态发育的个体则会向陆地扩散。学界普遍认为，这类发育过程的演化，由水生与陆生栖息环境的利弊权衡所驱动。在此研究背景下，我们旨在验证下述假说：气候驱动因子会影响表型转换（phenotypic transition）及其性别间差异——因自然种群中存在性别比例偏倚的情况。通过重复实验室实验，我们发现：当可利用水资源减少时，幼态延续的掌状真螈（Lissotriton helveticus）的变态发生率显著升高；而在该实验条件下，温度升高时其变态时间会提前。所有响应均存在性别偏倚，雄性比雌性更易发生表型转换。本研究阐明了气候变量如何影响兼性幼态延续，并为“生命倾向于陆生而非水生”的理论模型提供了实验支撑。此外，相较于雌性，雄性更频繁且更早地完成变态并脱离水体——这一结果首次为“雄性幼态延续现象罕见”的雄性逃逸假说（male escape hypothesis）提供了实验解释，并揭示了性别在幼态延续与变态发育演化过程中的重要作用。