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Microevolutionary Responses to Global Warming
Reference
Van Doorslaer, W., Stoks, R., Jeppesen, E. and De Meester, L. 2007. Adaptive microevolutionary responses to simulated global warming in Simocephalus vetulus: a mesocosm study. Global Change Biology 13: 878-886.

Background
The authors cite evidence that suggests that "populations may persist locally through phenotypic plasticity and microevolution of life history traits to deal with increasing temperature, which may buffer against changes in community structure," but they say that as far as they know, "there are no studies using experimental evolution experiments simulating global warming to rigorously evaluate the potential of populations to genetically adapt to global warming." Hence, they proceed to fill this important gap.

What was done
As they describe it, Van Doorslaer et al. say they "combined the realism and rigid, replicated experimental design of a large-scale mesocosm study where populations of the zooplankter Simocephalus vetulus were exposed for 1 year to different global warming scenarios" - (1) unheated control, (2) IPCC scenario A2, and (3) A2+50% downscaled to the regional level, where A2 refers to predicted temperatures for the period 2071-2100 - "with a life table experiment under laboratory conditions at three temperatures [18, 22 and 26C] that eliminated confounding, nongenetic factors."

What was learned
Van Doorslaer et al. say they "were able to demonstrate a rapid microevolutionary response (within 1 year) in survival, age at reproduction and offspring number to elevated temperatures in S. vetulus populations inoculated in large mesocosms," and they state that "these responses may allow the species to maintain itself under the forecasted global warming scenarios, as evidenced by the persistence of S. vetulus populations in the mesocosms under all three climate scenarios [our italics]." In addition, they report finding an approximate "five times higher survival at 26C of clones exposed for 1 year to global warming scenario A2+50% compared with clones exposed to the unheated control temperature regime," which observation, in their words, "strongly indicates rapid microevolution of the ability to cope with higher temperatures."

What it means
The four researchers say their results "provide solid proof for a rapid microevolutionary response to global warming in both survival and the subcomponents of individual performance (age at reproduction and number of offspring), which may allow populations of S. vetulus to persist locally under predicted scenarios of global warming." They also state that "such microevolutionary responses may buffer changes in community structure under global warming and help explain the outcome of previous mesocosm studies finding only marginal effects of global warming at the community level."

Reviewed 24 October 2007