Deterministic Plio-Pleistocene extinctions in the European cool-temperate tree flora

Extinctions have been important in the shaping of modern phytogeographic patterns. A classic example is the heavy Plio-Pleistocene losses that have caused Europe to have a depauperate temperate tree flora compared to eastern North America and eastern Asia. To investigate the mechanisms involved in this extinction event, I test the hypothesis that the present European status (extinct, relictual, or widespread) of cool-temperate tree genera found in Pliocene Europe is predictable from their modern climatic requirements. As a prerequisite for this analysis, I test for genus-level conservatism in climatic requirements by comparing congeneric values across Europe, eastern Asia and North America, and find strong evidence hereof. I find a high degree of ecological determinism in the fate of European Pliocene tree genera, still widespread taxa being more tolerant of cold growing season and winter temperatures than extinct and relictual taxa, and relictual taxa being more drought tolerant than extinct taxa.