Data from: Do stressful conditions make adaptation difficult? Guppies in the oil-polluted environments of southern Trinidad

The ability of populations to rapidly adapt to new environments will determine their future in an increasingly human-modified world. Although meta-analyses do frequently uncover signatures of local adaptation, they also reveal many exceptions. We suggest that particular constraints on local adaptation might arise when organisms are exposed to novel stressors, such as anthropogenic pollution. To inform this possibility, we studied the extent to which guppies (Poecilia reticulata) show local adaptation to oil pollution in southern Trinidad. Neutral genetic markers revealed that paired populations in oil-polluted versus not-polluted habitats diverged independently in two different watersheds. Morphometrics revealed some divergence (particularly in head shape) between these environments, some of which was parallel between rivers. Reciprocal transplant experiments in nature, however, found little evidence of local adaptation based on survival and growth. Moreover, subsequent laboratory experiments showed that the two populations from oil-polluted sites showed only weak local adaptation even when compared to guppies from oil-free northern Trinidad. We conclude that guppies show little local adaptation to oil pollution, which might result from the challenges associated with adaptation to particularly stressful environments. It might also reflect genetic drift owing to small population sizes and/or high gene flow between environments.

种群快速适应新环境的能力，将决定它们在日益受人类活动干扰的全球环境中的存续前景。尽管荟萃分析（meta-analyses）时常能检出本地适应的信号，但也揭示了大量不符合预期的例外情况。我们认为，当生物体暴露于新型胁迫因子（如人为污染）时，可能会对本地适应形成特定的约束。为验证这一假说，我们以特立尼达南部的孔雀鱼（Poecilia reticulata）为研究对象，探究其对石油污染的本地适应程度。中性遗传标记（neutral genetic markers）分析结果显示，在两个独立的流域中，受石油污染与未受污染栖息地的成对种群均发生了分化。形态计量学（morphometrics）分析发现，两类生境的种群间存在一定形态差异（尤以头部形状为甚），其中部分差异在两条河流间呈现出趋同特征。然而，野外互惠移植实验（reciprocal transplant experiments）结果表明，基于存活率与生长指标，几乎无证据支持本地适应现象。进一步的实验室实验显示，即便与来自特立尼达北部无石油污染区域的孔雀鱼种群相比，两个取自石油污染位点的种群也仅表现出微弱的本地适应。综上，我们认为孔雀鱼对石油污染的本地适应程度极低，这一现象可能源于极端胁迫环境下的适应挑战，也可能源自种群规模偏小引发的遗传漂变，或是不同生境间较高的基因流水平。