Monday, November 22, 2010

Evolutionary causes and consequences of plasticity

Changes in phenotype directly induced by the environment, called phenotypic plasticity, can have strong evolutionary consequences. Recent papers from the Hendry lab have examined plasticity-evolution relationships (Crispo et al., 2010, EER 12: 47-66; Thibert-Plante & Hendry, in press, JEB).

Crispo et al. conducted a meta-analysis to determine whether phenotypic plasticity generally tends to evolve as a response to human-induced changes to the environment. They examined 20 studies in which plasticity was estimated between populations that were under the influence of anthropogenic stressors, and between closely related populations that had not. They found that it many cases, plasticity had evolved in response to anthropogenic disturbance, when compared to their non-disturbed counterparts. The direction of this change, however, varied greatly among taxa and trait types. For example, invertebrates often showed the evolution of increased plasticity in life history traits and decreased plasticity in morphology, whereas plants showed no trends in plasticity evolution. The authors therefore conclude that plasticity and its evolution might be important for adaptation, but that it should be examined on a case-by-case basis, rather than making general statements about whether increased or decreased plasticity is likely to evolve as an adaptive strategy. The full article can be found at http://www.evolutionary-ecology.com/abstracts/v12/n01/ffar2517.pdf.

Thibert-Plante and Hendry looked at the consequences of phenotypic plasticity on ecological speciation. The consequences of plasticity for ecological speciation depend on the timing of dispersal relative to the expression of the plasticity. On the one hand, if plasticity is expressed early in development, before any dispersal, the individuals dispersing to a different environment will have reduced fitness, relative to the case of no plasticity. On the other hand, if plasticity is expressed after dispersal, the fitness cost of dispersing can be greatly reduced or even completely removed. Those facts are of great importance in the context of ecological speciation, where we study the rise and fall of barriers to gene flow among populations. More details can be found at http://onlinelibrary.wiley.com/doi/10.1111/j.1420-9101.2010.02169.x/abstract.

Xavier Thibert-Plante (FQRNT and NIMBioS postdoctoral fellow, Knoxville)

Erika Crispo (NSERC postdoctoral fellow in Royal Ontario Museum, Toronto)

* The authors have no competing interest, apart from space in high profile scientific journals.

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