Integrating ecological dynamics, population genetics and landscape structure in a theoretical study of range shifting.

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Predicting how species will respond to climate change is one of the greatest challenges facing biologists today. We want to be able to predict whether a species will be able to adapt within its current range to changing climatic conditions, or whether it will be able to move to new regions as they become climatically suitable. Evidence for British butterflies suggests that some species are already moving northwards as the climate warms, while others appear not to be responding as fast. Why might different species behave differently? There are many possible reasons, and few of these are currently included in models that make predictions regarding the future distribution of species. Most models that make predictions regarding future species distributions consider one species in isolation and use a climate envelope approach - essentially they establish the climatic conditions occupied by a species today and predict that the species will occur wherever that climate is found in the future. This method provides a good starting point, but it ignores several biological processes that may be extremely important. For example. some species may be poor at dispersing and may not be able to alter their range as rapidly as the climate change. There are likely to be interactions between species; a butterfly may have very good dispersal abilities but if its food plant doesn't, then the range shifting of the food plant may impose a limitation. Evolutionary processes may also be important, and it is these that this work will investigate. An existing ecological model will be extended so that incorporates genetic and evolutionary processes. Initially we will introduce neutral genetic diversity - that is alternate genes that do not modify an organisms fitness will be present within different individuals. We will look to see how the degree of neutral genetic diversity within a population changes during a period of climate change due to species changing their distributions. We will also introduce adaptation to local environmental conditions, and run simulation experiments to see how it modifies a species ability to keep pace with the change. Some species are already being observed to evolve such that they are able to change their ranges more rapidly. For example, some butterflies and crickets have involved increased dispersal ability as they move northwards through Britain. We will use our model framework to investigate how other characteristics might be expected to evolve during a period of climate change.