Real-World Rapid Evolutionary Response to Recent Real-World Warming
Thompson, J., Charpentier, A., Bouguet, G., Charmasson, F., Roset, S. Buatois, B., Vernet, P. and Gouyon, P.-H. 2013. Evolution of a genetic polymorphism with climate change in a Mediterranean landscape. Proceedings of the National Academy of Sciences 110: 2893-2897.
To test the hypothesis that phenolic chemotypes (thymol and carvacrol) of Mediterranean wild thyme (Thymus vulgaris) now occur in sites where they were previously absent or have increased their frequency in transitional sites due to a relaxation of selection normally associated with extreme early-winter freezing temperatures, Thompson et al. compared the chemotype composition of populations observed in the early 1970s (Vernet et al., 1977) to that found in 2009-2010 for 36 populations sampled along six transects in and around the Saint Martin-de-Londres basin, which covers an area of approximately 80 km2 and whose southern limits are about 20 km north of Montpellier in the Mediterranean climate region of southern France.
Based on their analysis, the eight French researchers report that they discovered "a rapid and probably ongoing spatial reorganization of a genetic polymorphism that is closely associated with a warming of extreme winter freezing events on a highly localized spatial scale," observing "both a significant appearance of freezing-sensitive phenolic chemotypes in sites where they were historically absent and an increase in their frequency in previously mixed populations."
Thompson et al. conclude that their study, "done over a similar time span as work reporting ecological changes in plant species distribution, illustrates that a rapid evolutionary response to temperature modifications can occur where genetic variation is combined with a change in a previously strong selection pressure, even for a perennial woody plant."
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