title: Environment, area, and diversification in the species-rich flowering plant family Iridaceae.
abstract: Phylogenetic analyses provide a means to explore evolutionary explanations for regional variation in species richness. The environment might also explain much of the previously unexplained imbalance of phylogenetic trees. We use data on geographic distribution and phylogenetic affinity to examine correlates of species richness among genera of irises (family: Iridaceae). Irises display strong phylogenetic imbalance, with a few clades containing a disproportionate number of species, most notably those found in the dry Mediterranean climate of the Cape of South Africa. The abiotic environment and area are strong predictors of iris species richness, but environment alone is insufficient to explain the high diversity of Cape clades. One possible explanation is that the interaction between biological traits and environment resulted in the unusually high diversification rates in the region.
authors.affiliation: Division of Biology and Natural Environmental Research Council Centre for Population Biology, Imperial College London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, United Kingdom. j.davies@virginia.edu
authors.forename: T Jonathan
authors.initials: TJ
authors.lastname: Davies
authors.forename: Vincent
authors.initials: V
authors.lastname: Savolainen
authors.forename: Mark W
authors.initials: MW
authors.lastname: Chase
authors.forename: Peter
authors.initials: P
authors.lastname: Goldblatt
authors.forename: Timothy G
authors.initials: TG
authors.lastname: Barraclough
mesh_terms: D044822:Biodiversity; D004777:Environment; D019143:Evolution, Molecular; D005843:Geography; D027621:Iridaceae / Q000235:genetics*; D008954:Models, Biological; D010802:Phylogeny