Adaptation, Extinction and Global Change

Prof. Graham Bell,

Department of Biology

April 2, 2008

Two kinds of environmental change will occur during the next hundred years. The first is a rapid increase in atmospheric carbon dioxide, perhaps doubling the current concentration. The second involves the indirect effects of elevated carbon dioxide levels, including climate change. Organisms may be able to tolerate these changes with little or no harm, or they may move from where they are now living to a more suitable region. If neither of these is possible, however, they will either adapt to the new conditions through natural selection, or they will become extinct. Whether a population can adapt depends on how rapidly environmental change occurs and on how severe it is. It also depends on the amount of genetic variation in the population, which will be proportional to the population size. We can use these concepts to predict whether "evolutionary rescue" is likely to mitigate the effects of global change on biodiversity. I shall describe some examples of rapid evolution as well as situations where adaptation has failed to occur, and I shall explain how organisms are likely to evolve in the coming period of rapid environmental change.

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