Experiments on a small seashore animal suggest that evolutinary changes cannot rescue animals and plants from the threat posed by climate change. The study provides a first answer to a question a lot of scientists have been talking about according to co-author Eric Sanford. “Do organisms have the ability to adapt to climate change on a timescale of decades?”
The extent to which acclimation and genetic adaptation might buffer natural populations against climate change is largely unknown. The critical point is that many organisms are already at their environmental limits, and natural selection won’t necessarily rescue them. This empirical study is one of few which have characterized genetic variation in traits directly related to environmental tolerance limits. The chosen organism was the broadly distributed tidepool copepod Tigriopus californicus. Ten generations were reared under laboratory conditions using thermal selection pressure, trying to quantify thermal tolerance and select for more heat-tolerant animals.
The copepods, that originated from eight different geographical locations, showed limited capacity to buffer against further increases in temperature. Though copepods from different locations showed wide variablity in heat tolerance, within each population it was impossible to increase the heat tolerance further than a half-degree Celsius. This suggest that the genetic make-up of these different populations is not very broad, which prevents selection for a different trait. There is lack of available genes on population level that could support such natural selection, which is probably due to the fact that individual populations of copepods live very isolated in confined rocky areas off the coast. The results suggest that models assuming a uniform climatic envelope may greatly underestimate extinction risk in species with strong local adaptation. Unfortunately this could also be the case for many other species of animals and plants when their habitats have been fragmented, for instance by human activities. Grosberg, one of the study authors, said it like this: “The critical point is that many organisms are already at their environmental limits, and natural selection won’t necessarily rescue them.”
(Sources: Proceedings of the Royal Society B., published online before print 08.06.2011; website UCDAVIS, 08.06.2011)