History of a Latitudinal Diversity Gradient: Woody Plants in Europe 13,000-1000 Years B.P.

Abstract

A pollen atlas of Europe is used to estimate the taxonomic diversity (taxon richness) of woody plants between 40?N and 70?N between 13,000 and 1000 years before the present (Y.B.P.). A gradient of decreasing taxonomic diversity with increasing latitude has existed for woody plants in Europe since 13,000 Y.B.P. The slope of this diversity gradient increased through the Holocene and was half as steep 13,000 years ago as it was 1000 Y.B.P. The slope of the diversity gradient increased with time after the retreat of the ice sheet because the colonization rate for new woody taxa was higher in southern Europe than in northern Europe. An equilibrium pattern of taxon richness may have been reached 6000 Y.B.P. These results support the hypothesis that modern differences in the diversity of woody plants between higher and lower latitudes in Europe are mostly a consequence of contemporary climatic limits rather than of differences in the time available for colonization since the retreat of the ice sheet.