Slide 12: Historic pollen distributions
This shows the responses of two species, spruce and oak, to these past changes in climate from the last glacial maximum. It is clear that as the planet warmed and the ice sheet retreated, these species migrated relatively rapidly northwards into areas that better suited their physiology.
Davis, Mararet B., and Shaw, Ruth. (2001) "Range Shifts and Adaptive Responses to Quaternary Climate Change" Science Vol. 292 Issue 5517, p673-679