Browsing by Author "Gildenhuys, Enelge"
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- ItemUnravelling taxonomic uncertainties among balloon vine species within the genus Cardiospermum using a molecular approach(Stellenbosch : Stellenbosch University, 2013-12) Gildenhuys, Enelge; Le Roux, Johannes J.; Ellis, Allan G.; Carroll, Scott P.; Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology. DST-NRF Centre of Excellence for Invasion Biology.ENGLISH ABSTRACT: Alien invasive species are a global concern not only threating biodiversity, but also negatively impacting regional economies. Consequently research aimed at understanding the invasion process is crucial for management of invasive alien species to reduce these impacts. Identifying accurate natal ranges is the key first step for efficient alien plant management, especially biological control. Such knowledge may assist in selecting host-specific biological control agents and help prevent non-target impact on native species. A case in point is the genus Cardiospermum of which species have been extensively moved around the globe with two species now being possible widespread invaders (C. grandiflorum and C. halicacabum), and a third species (C. corindum) having significant invasion potential. However, in some regions the native statuses of these species are not clear, hampering management. In order to minimize potential non-target impacts it is prudent to determine the relationships between Cardiospermum taxa in unknown native ranges prior to the release of biological control agents. With this thesis I aim to review available literature on the genus Cardiospermum, determine potential spread to suitable habitats globally for selected taxa, resolve unknown native ranges in southern Africa, and investigate rapid speciation of an endemic Namib Desert species of balloon vine. Through exhaustive searches for available literature on the genus Cardiospermum I report on the biology and ecology of selected species within the genus, with special focus on the most widespread species. Specifically, using species distribution modelling I investigate the potential spread of C. halicacabum, C. corindum and C. grandiflorum globally and assess the accuracy with which this can be determined using known native ranges to predict current alien ranges. Results indicate that these species have significant potential to spread, though highlighting that species distribution modelling over-fit predicted suitable ranges when using native range data alone. To resolve uncertain native ranges of selected species within the genus I reconstructed a dated multi-gene phylogeny and chloroplast haplotype network to investigate relationships within and among Cardiospermum species. I conclude that C. halicacabum is non-native in southern Africa due to polyphyletic relationships among accessions, while C. corindum is native due to natural long distance dispersal as indicated by a single monophyletic southern African clade. The close relationship observed between C. corindum and the African species, C. pechuelii, lead to a population-level genetic investigation of these two taxa. For this, I constructed a multi-gene phylogeny, chloroplast haplotype network and conducted population genetic diversity analyses which all indicated that the African arid adapted taxa, C. pechuelii, endemic to the Namib Desert of Namibia, evolved from C. corindum following long distance dispersal from South America. This study firstly provides insights into the ecology and biology of Cardiospermum, warning against further introduction due to potential spread. Secondly I resolved the unknown native statutes of Cardiospermum species in southern Africa and, lastly, illustrated the origin of African C. pechuelii. My research findings have major implications for on-going biological research against C. grandiflorum in South Africa and cautions strongly against the release of already-identified biological control agents due to their potential non-target impacts.