Doctoral Degrees (Conservation Ecology and Entomology)

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Browsing Doctoral Degrees (Conservation Ecology and Entomology) by Subject "Agricultural pests -- Biological invasions"

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    Population genetic structure and abundance of two Ceratitis species (Tephritidae) of agricultural importance in South Africa
    (Stellenbosch : Stellenbosch University, 2014-12) Karsten, Minette; Addison, Pia; Terblanche, J. S.; Jansen van Vuuren, Bettine; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: Research in the field of biological invasions has increased dramatically in the last two decades, especially due to the impact of human activity such as, transport, travel and international trade. Different stages of invasion have been proposed, each stage posing different barriers that must be overcome by the organism for it to become established. For the prevention of new invasions and the formulation of a successful integrated pest management program (IPM), knowledge of natural species community assemblage, as well as movement patterns, temporal distribution and invasion pathways are critical. In this dissertation I make use of two agricultural important fruit fly species, Ceratitis capitata amd C. rosa, in the Tephritidae family in different stages of the invasion process using different research methods to (i) investigate seasonal variation in fruit fly abundance in orchards and natural vegetation in the Western Cape to determine whether natural vegetation is used as possible refugia; (ii) to investigate maccrogeographic population structure of C. capitata with a focus on southern Africa to reconstruct and test C. capitata’s invasion pathway using a Bayesian framework; (iii) to investigate the population genetic structure, using molecular and morphological markers, to estimate gene flow and dispersal ability of C. rosa in South Africa. Results showed that C. capitata was the most abundant species captured and Biolure® the most effective lure. The largest number of individuals of either species (C. rosa and C. capitata) were captured in austral autumn (March-May) in both orchards and natural habitat with low capture rates throughout the rest of the year. Orchards and natural habitats were significantly different with higher trap catches always found in orchards. Based on microsatellite markers, C. capitata showed a decrease in genetic diversity moving away from the native range (Africa) into the introduced range (Australia, Greece, Guatemala, Madeira). Moreover, there was a clear pattern of differentiation between the African continent and the rest of the world indicating low levels of genetic connectivity. High connectivity throughout the African continent is problematic as this suggests that new invasions will move and colonize new areas unimpeded after first introduction. Lastly, my results indicate that there is no population structure in C. rosa within South Africa. This indicates that there are high levels of connectivity between different pest-occupied sites within the country and suggests that area-wide pest management should be undertaken on a much larger, preferably country-wide, scale. My results are discussed in the framework of invasion biology as well as integrated pest management. In conclusion, when investigating biological invasions, information from organismal biology and ecology as well as molecular biology can be valuable to inform decision-making regarding prevention and mitigation of pest species.