Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA.
Integr Comp Biol. 2008 Dec;48(6):769-87. doi: 10.1093/icb/icn088. Epub 2008 Oct 23.
Populations of species that inhabit a range of environments frequently display divergent morphologies that correlate with differences in ecological parameters. The velocity of water flow (i.e., flow velocity) is a critical feature of aquatic environments that has been shown to influence morphology in a broad range of taxa. The focus of this study was to evaluate the relationship between flow velocity and shell morphology for males and females of the semi-aquatic freshwater turtle Pseudemys concinna. For both sexes, the carapace and plastron show significant morphological differences between habitats characterized by slow-flowing (i.e., lentic) and fast-flowing (i.e., lotic) water. In general, the most prominent pattern for both sexes is that the shells of individuals from lotic habitats are more streamlined (small height-to-length ratio) than the shells of individuals from lentic habitats. Of the two shell components (carapace and plastron), the carapace shows greater divergence between habitats, particularly for males. These results are consistent with adaptations to flow velocity, and suggest that variation in shape may be more constrained in females. I also provide empirical evidence for an adaptive benefit of the observed shape change (i.e., drag reduction) and a brief comment on the relative roles of genetic divergence and phenotypic plasticity in generating shape differences observed in this species.
栖息在不同环境中的物种群体通常表现出与生态参数差异相关的不同形态。水的流速（即流速）是水生环境的一个关键特征，已被证明会影响广泛的分类群的形态。本研究的重点是评估流速与半水生淡水龟 Pseudemys concinna 雌雄个体壳形态之间的关系。对于两性，甲壳和腹甲在以缓慢流动（即静水）和快速流动（即激流）为特征的栖息地之间表现出显著的形态差异。一般来说，两性中最突出的模式是来自激流栖息地的个体的壳更流线型（高度与长度的比例较小），而来自静水栖息地的个体的壳流线型较差。在这两个壳成分（甲壳和腹甲）中，甲壳在栖息地之间的差异更大，特别是对于雄性。这些结果与对流速的适应一致，并表明形状的变化在雌性中可能受到更多限制。我还提供了观察到的形状变化（即减少阻力）的适应益处的实证证据，并简要讨论了遗传分化和表型可塑性在产生该物种观察到的形状差异中的相对作用。
