title: Ecology limits the diversity of the Cape flora: phylogenetics and diversification of the genus Tetraria.
abstract: Understanding the ecology and evolution of the hyper-diverse Cape flora is dependent on developing an understanding of its component parts, best epitomized by the Cape floral clades that have diversified and are largely endemic to the region. Here we employ a new dated phylogenetic hypothesis for the sedge genus Tetraria, one of the smaller Cape floral clades, to develop an understanding of timing and rates of diversification in the group. Specifically, we test whether diversification in Tetraria slowed as the number of extant lineages increased, suggesting that available ecological niche space has become increasingly saturated through time. The radiation of Tetraria began approximately 18million years ago, concordant with that of many other Cape clades. Diversification rates in the genus showed no drastic shifts in response to major environmental changes, but declined as lineage diversity accumulated, indicative of ecological limitation on speciation rates. This allows the development of heuristic predictions about the composition of Tetraria assemblages at various spatial scales, and suggests that closely related species should either be ecologically differentiated or have non-overlapping geographic distributions. The question of whether ecological limitation of diversity is a common phenomenon in other Cape lineages has important implications for our understanding of the evolution and ecology of the contemporary Cape flora as a whole.
authors: Fynbos Node, South African Environmental Observation Network, Private Bag X7, Rhodes Drive, Newlands 7735, South Africa; Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa. Electronic address: jasper@saeon.ac.za.
authors: Jasper A
authors: JA
authors: Slingsby
authors: Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa; Department of Integrative Biology, University of California, Berkeley, CA 94720, USA.
authors: Matthew N
authors: MN
authors: Britton
authors: Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa.
authors: G
authors: G
authors: Anthony Verboom
mesh_terms: D029785:Cyperaceae / Q000235:genetics*; D018744:DNA, Plant / Q000235:genetics; D017753:Ecosystem; D005819:Genetic Markers; D014644:Genetic Variation; D010802:Phylogeny; D017422:Sequence Analysis, DNA
chemical_list: D018744:DNA, Plant; D005819:Genetic Markers
keywords: Diversity dependence; Ecological niche saturation; Greater Cape Floristic Region; Mediterranean climate