Ecology limits the diversity of the Cape flora: Phylogenetics and diversification of the genus Tetraria
Published on Mar 1, 2014in Molecular Phylogenetics and Evolution3.99
· DOI :10.1016/j.ympev.2013.11.017
abstract Understanding the ecology and evolution of the hyper-diverse Cape ﬂora is dependent on developing anunderstanding of its component parts, best epitomized by the Cape ﬂoral clades that have diversiﬁed andare largely endemic to the region. Here we employ a new dated phylogenetic hypothesis for the sedgegenus Tetraria, one of the smaller Cape ﬂoral clades, to develop an understanding of timing and ratesof diversiﬁcation in the group. Speciﬁcally, we test whether diversiﬁcation in Tetraria slowed as the num-ber of extant lineages increased, suggesting that available ecological niche space has become increasinglysaturated through time. The radiation of Tetraria began approximately 18 million years ago, concordantwith that of many other Cape clades. Diversiﬁcation rates in the genus showed no drastic shifts inresponse to major environmental changes, but declined as lineage diversity accumulated, indicative ofecological limitation on speciation rates. This allows the development of heuristic predictions aboutthe composition of Tetraria assemblages at various spatial scales, and suggests that closely related speciesshould either be ecologically differentiated or have non-overlapping geographic distributions. The ques-tion of whether ecological limitation of diversity is a common phenomenon in other Cape lineages hasimportant implications for our understanding of the evolution and ecology of the contemporary Capeﬂora as a whole. 2013 Elsevier Inc. All rights reserved.