Flowering Plants through Time and Space: Key Innovations, Climate and Chance

The flowering plants represent one of the largest terrestrial evolutionary radiations within recent geological times. Current estimates indicate there may be as many as half a million extant species, yet within the angiosperms species richness can vary over several orders of magnitude between closely related clades and between geographical regions. Understanding why some regions and some lineages contain more species than others has been a major challenge in biology. To date, approaches for studying these two patterns have been mostly separate. Traditional explanations for 9579_C010.fm Page 149 Saturday, November 11, 2006 11:54 AM © 2007 by Taylor & Francis Group, LLC 150 Reconstructing the Tree of Life taxonomic imbalance have focused upon key biological traits, whilst regional variation in species richness has been ascribed largely to environmental factors. Using a tree of life for flowering plants, we demonstrate that environment can explain much of the taxonomic imbalance evident within phylogenetic trees not explained by key traits, and unequal rates of diversification, a product of the interaction between traits and environment, may contribute to regional patterns in species richness.