ABSTRACT
Species Richness ............................................................................................................... 155 10.4.1 Biomass Theory ................................................................................................... 155 10.4.2 Faster Evolution Hypothesis ................................................................................ 155 10.4.3 Evaluating the Faster Evolution Hypothesis ....................................................... 156
10.5 Traits
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Environment: Diversification of Irises in the Cape of South Africa .............................................................................................. 157
10.6 Conclusions........................................................................................................................ 159 Acknowledgements ...................................................................................................................... 160 References .................................................................................................................................... 160
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
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.
One of the principal goals of ecology and evolutionary biology is to understand the diversity and distribution of life on Earth. The expansion of molecular approaches to phylogenetics has provided a wealth of data for reconstructing the evolutionary events behind why some groups have flourished whilst others have floundered. Flowering plants (angiosperms) have been one focus for such studies. Flowering plants represent a highly species rich group with an estimated 500,000 extant species
