Lizards demonstrate rapid evolution in the face of extreme cold
By studying a population of lizards before and after a sudden cold snap that struck the U.S., scientists have observed how the surviving population underwent rapid adaptation in response to the event. The results demonstrate how a subpopulation can respond quickly – even in one generation – to extreme climatic events. The first direct measurement of natural selection influencing a wild population following a short-lived but extreme climatic event was reported in 1898 by biologist Hermon Bumpus, who found that the size of sparrows changed in response to a severe snowstorm. Yet, despite technological advances, there are still surprisingly few examples of biological response to intense weather events. Here, Shane C. Campbell-Staton and colleagues measured the threshold temperature at which the green anole lizard, Anolis carolinensis, loses its coordination, at five sites across Texas in August 2013. They conducted the same measurements following an extreme cold snap during the winter of 2013-2014, which drove temperatures that were significantly colder than the previous 15 years. Yet they found that the surviving lizards in the south displayed greater resistance to lower temperatures than they had before the cold snap, at levels similar to their more northern counterparts. Furthermore, RNA sequencing revealed 14 genomic regions that displayed significant divergence between individuals before and after the storm. Intriguingly, the shift in gene expression only occurred in the southern population, which displayed a genetic shift toward the more northerly populations; the northern populations, in contrast, showed no change, presumably because winter variability there was less severe. These results are highlighted in a Perspective by Peter R. Grant.
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