Temperature-based population segregation in birch

Mean temperature of establishment years for warm- and cold-year subpopulations of a naturally occurring stand of Betula pendula (birch) shows a difference equivalent to that between current temperatures and temperatures projected for 35-55 years hence, given 'business as usual.' The existence of 'pre-adapted' individuals in standing tree populations would reduce temperature-based advantages for invading species and, if general, bring into question assumptions currently used in models of global climate change. Our results demonstrate a methodology useful for investigating the important ecological issue of adaptation vs. range shifts as a means of response to climate change.