Data from: Shape variation in the least killifish: ecological associations of phenotypic variation and the effects of a common garden

Studies of the adaptive significance of variation among conspecific populations often focus on a single ecological factor. However, habitats rarely differ in only a single ecological factor, creating a challenge for identifying the relative importance of the various ecological factors that might be maintaining local adaptation. Here we investigate the ecological factors associated with male body shape variation among nine populations of the poeciliid fish, Heterandria formosa, from three distinct habitats and combine those results with a laboratory study of three of those populations to assess the contributions of genetic and environmental influences to shape variation. Field-collected animals varied principally in three ways: the orientation of the gonopodium, the intromittent organ; the degree of body depth and streamlining; and the shape of the tail musculature. Fish collected in the spring season were larger and had a more anteriorly positioned gonopodium than fish collected in autumn. Fish collected from lotic springs were larger and more streamlined than those collected from lentic ponds or tidal marshes. Some of the variation in male shape among populations within habitats was associated with population-level variation in species richness, adult density, vegetative cover, predation risk, and female standard length. Population-level differences among males in body size, position of the gonopodium, and shape of the tail musculature were maintained among males reared in a common environment. In contrast, population variation in the degree of streamlining was eliminated when males were reared in a common environment. These results illustrate the complicated construction of multivariate phenotypic variation and suggest that different agents of selection have acted on different components of shape.

针对同种种群间变异的适应意义的研究，通常仅聚焦于单一生态因子。然而自然生境极少仅在单一生态因子上存在差异，这为识别可能维持局部适应的各类生态因子的相对重要性带来了挑战。本研究针对来自三类不同生境的9个花鳉科（Poeciliidae）鱼类异口鳉（Heterandria formosa）种群的雄性体型变异相关的生态因子展开探究，并结合针对其中3个种群的实验室饲养实验，以评估遗传与环境因素对体型变异的贡献。野外采集的雄性个体主要在三方面存在差异：交配足（gonopodium，intromittent organ）的朝向、体高与流线型程度，以及尾部肌肉形态。春季采集的个体体型更大，且交配足位置更靠前，相较于秋季采集的个体。采集自流水生境泉眼（lotic springs）的雄性个体体型更大、流线型程度更高，相较于采集自静水池塘（lentic ponds）或潮汐沼泽的个体。同种生境下不同种群间的雄性体型变异，部分与物种丰富度、成体密度、植被覆盖度、捕食风险以及雌性标准体长的种群水平差异相关。在共同环境下饲养的雄性个体中，种群间在体型大小、交配足位置以及尾部肌肉形态上的差异依然得以保留。与之相反，雄性流线型程度的种群差异在共同环境饲养后消失。本研究结果揭示了多变量表型变异的复杂构成，并表明不同的选择因子对体型的不同组分产生了差异化的选择作用。