Constraints to adaptation: The “oily guppies” of southern Trinidad

This post is from Gregor Rolshausen

Arguably, among the most interesting shifts in evolutionary thinking in the past decades is an increased recognition of the limits on rates, directions, and outcomes of evolution. For instance, classic expectations of the adaptive process, such as trait divergence between environments and higher fitness of local vs. non-local individuals, are often not met in natural populations. Effective local adaptation might be hampered by migration and maladaptive gene flow that drags population away from local fitness peaks. Furthermore, instances of (local) maladaptation appear to be particularly pronounced in the context of abrupt and extensive anthropogenic disturbance such as climate change, habitat fragmentation, or pollution. An understanding of the constraints to evolutionary dynamics on the population level therefore needs to become an important cornerstone of ongoing conservation efforts and biodiversity management plans. I here review a recent empirical study from the Hendry lab that investigates constraints to local adaptation in natural fish populations and reveals some interesting contradictions to classical expectations of local adaptation: the “oily guppies” (Poecilia reticulata) of southern Trinidad – a system in which severe crude-oil pollution has a strong impact on the condition of seemingly locally adapted populations.

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