Evolutionary history affects adaptation at the rear edge
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Proposed Symposium Title: Evolutionary history affects adaptation at the rear edge
Laura F. Galloway1
Affiliations: 1 Department of Biology, University of Virginia, Charlottesville VA, USA
How past evolutionary dynamics have shaped range limits remains a central and timely question in ecology and evolutionary research, especially when predicting how species ranges will respond to future climates. The rear edge – remnant populations persisting in former glacial refugia – is particularly exposed to climate change as these populations often occur at the warmer range limits. However, this range limit is largely overlooked in evolutionary research so we lack a clear picture of how past evolutionary dynamics may affect adaptation in these populations. Rear-edge populations may have served as distinct genetic diversity reservoirs during successive glaciation periods. High genetic diversity and differentiation may have provided beneficial variation to adapt to continuously warming post-glacial climates and will be crucial for the ability of these populations to persist and adapt to future climates. At the same time, rear-edge populations may be at particular risk for extinction, as strong genetic drift resulting from a history of demographic decline and isolation in marginal habitats may reduce their genetic diversity and constrain adaptation. This interplay of opposing evolutionary forces may result in a mosaic of adaptive capacities at species’ rear edges. Here we assessed how past evolutionary dynamics shape climate adaptation at the rear edge of the North American herb Campanula americana. We studied populations from the core and the rear edge and found greater phenotypic differentiation among populations and greater adaptation to the marginal climates in rear-edge populations. These results will be discussed in a climatic, population genetic and phylogenetic context.