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，将决定它们在人类活动日益改造的世界中的未来存续前景。尽管元分析常能揭示本地适应的特征，但也屡屡发现诸多例外。我们提出，当生物暴露于新型胁迫因子（如人为污染）时，可能会对本地适应产生特定限制。为探究这一可能性，我们研究了特立尼达南部的孔雀鱼（Poecilia reticulata）对石油污染的本地适应程度。中性遗传标记分析显示，两个不同流域内，石油污染生境与未污染生境中的配对种群均发生了独立分化。形态计量学分析发现，两类生境间存在一定程度的形态分化（尤其在头部形状方面），且部分分化特征在两条河流间呈现平行演化趋势。然而，野外互易移植实验基于存活与生长指标，未发现本地适应的显著证据。此外，后续室内实验显示，即便与来自特立尼达北部无石油污染区域的孔雀鱼相比，两处石油污染生境的种群仅表现出微弱的本地适应能力。综上，我们认为孔雀鱼对石油污染的本地适应能力极弱，这一现象可能源于极端胁迫环境下的适应挑战，也可能归因于种群规模过小引发的遗传漂变，抑或是不同生境间存在较高的基因流。