OOS 89

Evolutionary Responses to Directional Climate Change

Faced with rapid, directional climate change, species adapted to a particular zone have to acclimate physiologically, migrate, evolve, or go locally extinct. Although range shifts are an important component of species response to changing climate, adaptive responses may be of equal importance. Locally adapted populations or ecotypes have been identified for many species and may constitute a reserve of genetic variation that will help species persist in the face of rapid climate change. However, genetic specialization is a double-edged sword, as reduced genetic variation within populations may limit in situ adaptive potential. This session will examine the potential and realized consequences of climate change for populations of plants and animals. As the climate changes, many locally adapted populations are likely to experience reduced fitness. For example, one potential consequence of local adaptation is adaptational lag, in which populations under selection due to a changing climate fail to adapt because of insufficient variation within the population or low gene flow from better-adapted populations. Another consequence may be reduced or enhanced gene flow, depending on the presence or absence of pollinators and dispersal agents. This session will present case studies that illustrate evolutionary responses of a diverse group of organisms, including herbaceous species, insects, fish, and birds. The studies encompass a similar variety of ecosystems, including Arctic tundra, eastern deciduous forest, grasslands, montane ecosystems and the ocean.