Browsing by Author "Gildenhuys, Enelge"

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    The ecology, biogeography, history and future of two globally important weeds : Cardiospermum halicacabum Linn. and C. grandiflorum Sw.
    (Pensoft, 2013-10-11) Gildenhuys, Enelge; Ellis, Allan G.; Carroll, Scott P.; Le Roux, Johannes J.
    Members of the balloon vine genus, Cardiospermum, have been extensively moved around the globe as medicinal and horticultural species, two of which are now widespread invasive species; Cardiospermum grandiflorum and Cardiospermum halicacabum. A third species, Cardiospermum corindum, may also have significant invasion potential. However, in some regions the native status of these species is not clear, hampering management. For example, in South Africa it is unknown whether Cardiospermum halicacabum and Cardiospermum corindum are native, and this is a major constraint to on-going biological control programmes against invasive Cardiospermum grandiflorum. We review the geography, biology and ecology of selected members of the genus with an emphasis on the two most widespread invaders, Cardiospermum halicacabum and Cardiospermum grandiflorum. Specifically, we use molecular data to reconstruct a phylogeny of the group in order to shed light on the native ranges of Cardiospermum halicacabum and Cardiospermum corindum in southern Africa. Phylogenetic analyses indicate that southern African accessions of these species are closely related to South American taxa indicating human-mediated introduction and/or natural long distance dispersal. Then, on a global scale we use species distribution modelling to predict potential suitable climate regions where these species are currently absent. Native range data were used to test the accuracy with which bioclimatic modelling can identify the known invasive ranges of these species. Results show that Cardiospermum species have potential to spread further in already invaded or introduced regions in Australia, Africa and Asia, underlining the importance of resolving taxonomic uncertainties for future management efforts. Bioclimatic modelling predicts Australia to have highly favourable environmental conditions for Cardiospermum corindum and therefore vigilance against this species should be high. Species distribution modelling showed that native range data over fit predicted suitable ranges, and that factors other than climate influence establishment potential. This review opens the door to better understand the global biogeography of the genus Cardiospermum, with direct implications for management, while also highlighting gaps in current research.
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    Fine-scale biogeography : tidal elevation strongly affects population genetic structure and demographic history in intertidal fishes
    (University of California, eScholarship, 2013) Von der Heyden, Sophie; Gildenhuys, Enelge; Bernardi, Giacomo; Bowie, Rauri C. K.
    Numerous studies have demonstrated population genetic structuring in marine species, yet few have investigated the effect of vertical zonation on gene flow and population structure. Here we use three sympatric, closely related clinid species, Clinus cottoides, C. superciliosus and Muraenoclinus dor‐ salis, to test whether zonation on South African intertidal rocky shores affects phylogeographic patterns. We show that the high‐shore restricted species has reduced gene flow and considerably higher FST val‐ ues (FST = 0.9) than the mid‐ and low‐shore species (FST < 0.14). Additionally, we provide evidence for remarkably different demographic and evolutionary histories, ranging from extreme population bottle‐ necks to population persistence, which are probably linked to effective population size and habitat spe‐ cialisation. This study further highlights the need for a multispecies approach to unravel the biological and evolutionary processes that drive extant population genetic patterns in marine species, as even closely related species with similar life histories show highly variable results.
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    Unravelling 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.