Climatic and geological change may play a key role in stimulating biological radiations. Here, we use phylogenetic data to test whether the comparatively high diversity of ehrharteoid grasses in the Cape region of South Africa is the result of rapid radiation associated with the onset of a seasonally arid climate during the late Miocene. A phylogenetic hypothesis based on morphological and nucleotide sequence (nuclear ITS1 and plastid trnL-F) data confirms the monophyly of the African Ehrharta species and shows that the diversification of this lineage was centered in the Cape region. Sequence divergence data (ITS1 trnL-F) indicate a pulse of rapid speciation, which may explain poor phylogenetic resolution within the African Ehrharta clade. Alternative calibrations yield a broad range of time estimates for the start and end of this radiation, most of which indicate a radiation inside the last 11 million years. A calibration based on the age of Ehrhartoideae suggests that radiation started 9.82 ± 0.20 million years ago and ended 8.74 ± 0.21 million years ago. Under alternative calibrations, estimated speciation rates during the period of radiation range between 0.87 and 4.18 species per million years. Parsimony optimization of habitat parameters reveals that radiation was correlated with the occupation of seasonally arid succulent karoo environments, wet heathy (fynbos) environments being ancestral. These data support earlier suggestions that late Miocene climatic change stimulated floristic radiation at the Cape, and highlight the potential importance of environmental change in powering diversification in continental floras.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.