In a study published in the September issue of The American Naturalist, T. Jonathan Davies (Imperial College London) and colleagues use a phylogenetic tree of the iris family to show that lineages within the Cape have speciated at a faster rate than those found elsewhere, even in comparison to regions of similar Mediterranean climates. Irises represent a family of herbaceous, seasonal geophytes, and it is perhaps these features and associated biological traits that have provided the key for lineages to prosper in the Cape region, thereby exploiting the potential for rapid diversification conveyed by the Cape environment. An appreciation of the interaction between biological traits and environment will likely prove critical to an understanding and interpretation of the distribution of species richness across the globe and among the branches of the tree of life.
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T. Jonathan Davies (Imperial College London), Vincent Savolainen (Royal Botanic Gardens), Mark W. Chase (Royal Botanic Gardens), Peter Goldblatt (Missouri Botanical Garden), and Timothy G. Barraclough (Imperial College London), "Environment, area and diversification in the species-rich flowering plant family, Iridaceae" 166:3 September 2005.