The latitudinal gradient of diversity through the Holocene as recorded by fossil pollen in Europe

To assess the impacts of Pleistocene glaciation on the latitudinal diversit y gradient, I examined plant family diversity during the last interglacial at 24 sites in Europe between 39 degrees and 71 degreesN latitude. Familial richness and turnover were calculated for 1000-year intervals for each sit e. Although familial turnover varied from 6 to 59% per 1000 years, familial richness remained essentially constant at 16 (67%) of the sites. For the r emaining sites, the rates of change of richness were very low (2-3 families per 1000 years) and were not associated with latitude. These results do no t support 'historical' hypotheses for the latitudinal diversity gradient, b ecause neither local species richness nor the slope of the gradient have ch anged meaningfully in the last 10,000 years. Instead, they support hypothes es that invoke contemporary mechanisms to explain the inverse relationship between latitude and diversity. Additionally, the lack of change both in ri chness at individual sites and in the latitudinal diversity gradient throug h time suggest that the ecological and evolutionary processes that regulate diversity within local communities operate in a systematic fashion across large spatial and temporal. scales. Future hypotheses for the latitudinal g radient of diversity should include universal rules that determine how reso urces are divided among species at local and global scales without regard t o the identify of particular species.