Masters Degrees (Plant Sciences)
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Browsing Masters Degrees (Plant Sciences) by Subject "African flora"
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Item Open Access Phylogeny of the genus raphionacme (Apocynaceae)(University of the Free State, 2013-07) Pienaar, Magdil; Visser, B.; Venter, A. M.; Jackson, M.English: The phylogeny and biogeography of Raphionacme were investigated in this first comprehensive study which included virtually all the species. Raphionacme is the largest genus in the subfamily Periplocoideae (Apocynaceae sensu lato) and consists of 36 species and two subspecies. Sequence data from the nuclear ITS gene region and 45 morphological characters were used to determine relationships between 30 Raphionacme species. Raphionacme is an African genus and widely distributed throughout this continent with the highest concentration of species in southern Africa, the Cape Floristic Region excluded. Only one species, R. arabica, is found outside Africa on the Arabian Peninsula. The most common habitat in which members of this genus occur is grassland or savanna. The majority of species are herbaceous geophytes, with four species that have a climbing habit. Four areas of species richness were identified. These are the Tongaland-Pondoland Mosaic in northeastern South Africa, which includes the Maputaland Centre of Endemism, the Zambezian Region, the Karoo-Namib Region and Kalahari-Highveld Transitional Zone both in the west of southern Africa. Nine endemic species were identified of which seven occur south of the Equator. These are R. chimanimaniana, R. elsana, R. haeneliae, R. namibiana, R. sylvicola, R. villicorona and R. zeyheri, with only R. moyalica occurring in the north of Kenya and R. arabica in Oman. The cladistic results of this investigation indicated that the first and therefore oldest clade to diverge contain species from southern Africa, leading to the assumption that Raphionacme originated in this region. The geophytic habit of the species would probably be an indication that this coincided with the aridification of this region. Thereafter diversification and radiation may have occurred northwards following the savanna that developed east and north of the remaining Equatorial rain forest. Some taxonomic implications, based on the phylogenetic results, have been included. The outgroup Schlechterella abyssinica was found to be nested in the Raphionacme clade, in both the molecular and combined cladograms. The removal of Raphionacme abyssinica to the genus Schlechterella would seem to have been incorrect and the species S. abyssinica may have to be returned to Raphionacme. Three Raphionacme species, R. bingeri, R. excisa and R. splendens were combined under the name R. splendens. Subsequently R. splendens was subdivided into two subspecies. The cladistical results of this study support the creation of Raphionacme splendens subsp. splendens and R. splendens subsp. bingeri.