In a widespread species, a matching of phenotypic traits to local environmental optima is generally attributed to site-specific adaptation. However, the same matching can occur via adaptive plasticity, without requiring genetic differences among populations. Adult sea kraits (Laticauda saintgironsi) are highly philopatric to small islands, but the entire population within the Neo-Caledonian Lagoon is genetically homogeneous because females migrate to the mainland to lay their eggs at communal sites; recruits disperse before settling, mixing up alleles. Consequently, any matching between local environments (e.g. prey sizes) and snake phenotypes (e.g. body sizes and relative jaw sizes (RJSs)) must be achieved via phenotypic plasticity rather than spatial heterogeneity in gene frequencies. We sampled 13 snake colonies spread along an approximately 200 km northwest–southeast gradient (n > 4500 individuals) to measure two morphological features that affect maximum ingestible prey size in gape-limited predators: body size and RJS. As proxies of habitat quality (HQ), we used protection status, fishing pressure and lagoon characteristics (lagoon width and distance of islands to the barrier reef). In both sexes, spatial variation in body sizes and RJSs was linked to HQ; albeit in different ways, consistent with sex-based divergences in foraging ecology. Strong spatial divergence in morphology among snake colonies, despite genetic homogeneity, supports the idea that phenotypic plasticity can facilitate speciation by creating multiple phenotypically distinct subpopulations shaped by their environment.

中文翻译：

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尽管 13 个蛇种群的遗传同质性，但可塑性使表型与当地条件相匹配

在广泛分布的物种中，表型性状与局部环境最优值的匹配通常归因于特定地点的适应。然而，相同的匹配可以通过适应性可塑性发生，而不需要群体之间的遗传差异。成年海金龟子 (Laticauda saintgironsi) 对小岛屿具有高度的嗜血性，但新喀里多尼亚泻湖内的整个种群在遗传上是同质的，因为雌性迁移到大陆在公共场所产卵；新兵在定居前分散，混合等位基因。因此，本地环境（例如猎物大小）和蛇表型（例如体型和相对颌骨大小（RJS））之间的任何匹配都必须通过表型可塑性而不是基因频率的空间异质性来实现。我们采样了 13 个沿西北-东南梯度约 200 公里（n > 4500 个体）分布的蛇群，以测量影响裂口受限捕食者最大可摄入猎物大小的两个形态特征：体型和 RJS。作为栖息地质量（HQ）的代表，我们使用了保护状态、捕鱼压力和泻湖特征（泻湖宽度和岛屿到堡礁的距离）。在两性中，体型和 RJS 的空间变化都与总部有关；尽管方式不同，但与觅食生态中基于性别的差异一致。尽管遗传同质性，蛇群之间形态的强烈空间差异支持表型可塑性可以通过创建由其环境塑造的多个表型不同的亚群来促进物种形成的观点。