Disturbances as hot spots of ecotypic variation: a case study with Dryas octopetala

Ecotypic specialization among populations within plant species can result in adaptational lag when the climate changes directionally. However, disturbances, whether caused by direct effects of human activities or indirect effects such as climate change, may represent zones within which natural selection is relaxed. We compared the genetically based variation in leaf morphology in Dryas octopetala within three natural populations arrayed along a snowbank gradient, to that found in a recently colonized gravel pad less than 100 m away (1600 total leaf lengths measured; 4 sites x 10 transects/site x 4 plants/transect x 10 leaves/plant). Elevated among-clone leaf length variation within the disturbed site supported the idea that disturbances may represent hotspots of evolutionarily significant genetic variation. In the Arctic, where colonization of disturbances is primarily by native species, adaptive evolution may be more rapid than previously thought due to relaxation of selection and subsequent mixing of previously isolated gene pools in such areas.