VERBOOM, G. ANTHONY* and H. PETER LINDER. Department of Botany, University of Cape Town, Private Bag, 7700 Rondebosch, South Africa. - Phylogenetics of the Cape grass genus Ehrharta (Ehrharteae): evidence for diversification in a summer-arid system.
Despite the richness of the Cape Flora, there are relatively few
published phylogenetic studies that investigate the origins of this
diversity. To address this, we estimated the phylogeny of a Cape grass
genus, Ehrharta, and used this to investigate its past
diversification. With 24 species, Ehrharta is much larger than
any other genus in its tribe, and shows a remarkable diversity of form
and ecological function that suggests adaptive radiation. Our
phylogenetic analyses included representatives of all four ehrharteoid
genera, and used three data sources: two molecular (ITS1 and trnL-F)
and one morphological. The results confirm the monophyly of Cape
Ehrharta species and provide a framework for reconstructing
historical shifts in the edaphic and climatic niches occupied by the
genus in the western Cape. Habitat reconstruction suggests that the
major diversification of the genus followed movement into habitats
experiencing more intense and prolonged summer aridity than those
inferred to be ancestral. At least some speciation within the Cape
arid zone may be linked to greater edaphic diversity here.
Key words: Cape Flora, Ehrharta, Poaceae, radiation