Evolutionary Response to Rapid Climate Change

The June 9 Science magazine has a perspectives article on what has led to changes in migration, development, and reproduction in numerous species as seasonal timing changes (spring begins earlier, winter later).

Phenotypic plasticity –

the ability of individuals to modify their behavior, morphology, or physiology in response to altered environmental conditions

explains some of the ability of species to respond to climate changes. Additionally, heritable genetic change is occurring in birds, squirrels, and mosquitoes.

Examples include earlier reproduction in Canadian red squirrels to take advantage of earlier spruce cone production. Blackcaps (birds) have a genetically distinct subpopulation which winters in Britain rather than Iberia. Another bird, the European great tit is moving its egg-laying date forward as caterpillars mature earlier in the year. North American mosquitoes that live in pitcher plants now initiate larval dormancy on days that are shorter, and the sun more southerly, than the cues from a few years ago, and take advantage of a longer growing season.

The genetic changes all relate to season:

earlier or more flexible timing of reproduction in squirrels and birds, later arrival of winter in mosquitoes, and a longer growing season for fruit flies.

Temperature change alone does not appear to be enough to cause a genetic response. Some of the new mosquitoes were moved to simulated new climates to test how they responded to various seasonal cues such as day length, and temperature, and temperature appeared not to be of great importance. Additionally, there appears to be no evidence of animals evolving for either greater heat tolerance of a higher optimal temperature. Part of the reason is that climate change is fastest in winter at high latitudes. [This article was published before this year’s long hot summer.]

Species show differing abilities to respond to climate change:

Small animals with short life cycles and large population sizes will probably adapt to longer growing seasons and be able to persist; longer life cycles and smaller population sizes will experience a decline in population size or be replaced by more southern species.

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