ABSTRACT: Heterogeneous environments pose a particular challenge for organisms because a single phenotype is unlikely to perform best across the variety of encountered stressors. To understand how species meet this challenge, we investigated the extent to which contrasting environmental pressures induced ecological and phenotypic responses in a natural population of a wide-dispersing marine snail at a small spatial scale. We analyzed several traits of Heleobia australis (Rissooidea: Cochliopidae) collected from heterogeneous, but highly connected, habitats from the intertidal area of the Bahía Blanca estuary, Argentina. We also conducted molecular analyses by amplifying the COI gene in individuals sampled from each habitat. We found that sympatric subpopulations of H. australis exhibited a strong phenotypic divergence in shell characters and body weight in response to thermal, saline, and dehydration stress, crab predation risk, and parasitic castrators. We proved that this differentiation occurred even early in life, as most of the characters observed in juveniles mirrored those found in adults. We also found a divergence in penis size in snails collected from each habitat and raised in common garden laboratory conditions. Molecular analyses confirmed that the individuals studied constituted a single species, despite the strong phenotypic differences among subpopulations. The small-scale phenotypic differentiation suggests that H. australis experienced a fine-grained environment where conditions imposed by different sources of stress favored the expression of beneficial traits. We discuss the role of plasticity in shaping adaptive phenotypic responses that increase the likelihood of persistence of subpopulations facing environmental stress conditions.

中文翻译：

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环境压力因素在广泛分布的海洋蜗牛中诱导强烈的小规模表型分化

摘要：异质环境对生物体构成特殊挑战，因为单一表型不太可能在遇到的各种压力源中表现最佳。为了了解物种如何应对这一挑战，我们研究了不同环境压力在小空间尺度上广泛分布的海洋蜗牛自然种群中引起生态和表型反应的程度。我们分析了从阿根廷 Bahía Blanca 河口潮间带区域的异质但高度连接的栖息地收集的Heleobia australis（Rissooidea：Cochliopidae）的几个特征。我们还通过扩增从每个栖息地采样的个体的 COI 基因进行分子分析。我们发现H. australis 的同域亚群对热、盐水和脱水胁迫、螃蟹捕食风险和寄生去势动物的反应在壳特征和体重方面表现出强烈的表型差异。我们证明这种分化甚至在生命早期就发生了，因为在青少年中观察到的大多数特征都反映了在成人中发现的特征。我们还发现从每个栖息地收集并在普通花园实验室条件下饲养的蜗牛的阴茎大小存在差异。分子分析证实，所研究的个体构成单一物种，尽管亚群之间存在强烈的表型差异。小规模的表型分化表明H . 澳大利亚经历了一个细粒度的环境，在这种环境中，不同压力来源施加的条件有利于有益特征的表达。我们讨论了可塑性在塑造适应性表型反应中的作用，这些反应增加了亚群面临环境压力条件的可能性。