Biogeography of Exormotheca pustulosa

The Rand flora is a biogeographical disjunction which refers to plant lineages occurring at the margins of the African continent and neighbouring oceanic archipelagos. Here, we tested whether the phylogeographic pattern of Exormotheca pustulosa Mitt. was the result of vicariance induced by the past climatic changes or the outcome of a series of recent long-distance dispersal events. Two DNA chloroplast and one nuclear marker were analysed. Phylogenetic and phylogeographical relationships were inferred as well as divergence time estimates and ancestral areas. Exormotheca originated in Eastern Africa during the Late Oligocene/Early Miocene while Exormotheca putulosa diversified during the Late Miocene. Three main E. pustulosa groups were found: the northern Macaronesia/Western-Mediterranean; the South Africa/Saint Helena and the Cape Verde. The major split events among these groups occurred during the Late Miocene/Pliocene; diversification is recent, dating back to the Pleistocene. Climate-driven vicariance and subsequent long-distance dispersal events may have shaped the current disjunct distribution of E. pustulosa that corresponds to the Rand Flora pattern. Colonisation of Macaronesia seems to have occurred twice by two independent lineages. The evolutionary history of E. pustulosa populations of Cape Verde warrants further study.