The microevolutionary consequences of climate change.

Species may respond to climate change by shifting in abundance and distribution, by going extinct, or by evolving. Predicting which will occur is difficult. Climate change may lead to alterations in both abiotic and biotic components of selection. Although there is evidence that abundant genetic variation exists in some species which can respond to such selection, other species seem to have little genetic variation for key characters determining distribution and abundance. Moreover, climate change can affect nonselective components of microevolution, such as genetic variances and covariances, and the magnitudes of drift, mutation and gene flow. There is almost no species for which we know enough relevant ecology, physiology and genetics to predict its evolutionary response to climate change.