Is it plastic or the real deal? Differentiating phenotypic plasticity from adaptive genetic change

threespine stickleback

Threespine stickleback one of the few species for which population studies showing adaptive genetic change meet all six of the suggested criteria.

Life’s resilience in today’s rapidly changing world is providing us with some fascinating insights into the mechanisms of evolution, genomic flexibility, and some hope (at least for some species under some conditions) for the future.   One challenge for those of us just trying to understand the importance of contemporary evolution for survival when faced with rapid environmental change is distinguishing between plasticity and adaptation.  A new review and analysis , “Monitoring adaptive genetic responses to environmental change” published in Molecular Ecology by Michael Hansen (and a long list of colleagues who are members of the Working Group on Genetic Monitoring, or GeM,) provides a comprehensive and accessible (for the non-evolutionary biologist, ecologist or other ‘ologists) survey of  adaptive responses  as well as some guidelines for determining whether population level changes are truly adaptive genetic responses.

Write the authors about the difference between plasticity and genetic adaptation:

Inferring adaptation from shifts in phenotype, however, runs the risk of confusing short-term, plastic responses with longer-term genetic changes. Most individuals have the capacity to respond to local environmental conditions via phenotypic plasticity…plasticity can also serve to provide an initial rapid response to environmental change that can then facilitate subsequent genetic adaptation via ‘genetic assimilation.’

…when environmental stresses reverse…phenotypic changes reflecting plasticity would also reverse rapidly, in contrast to genetic changes, which would be harder to reverse.

Yet neither plasticity nor genetic adaptive change is a panacea for avoiding extinction.  Populations can only “evolve” so quickly without straying too far from their “optimal phenotype,” too many changes too quickly can also lead to extinction. After reviewing a few key studies, the authors present results from an analysis of 44 studies (the details of which, along with the authors evaluation of each study in terms of meeting a number of key criteria for determining genetic adaptation, are available online).  For the full review see: Monitoring adaptive genetic responses to environmental change, Molecular Ecology (2012) 21:1311-1329 (its free!)

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