Abstract: The ecologically sensitive, but relatively simple sub-Antarctic mouse-colonised Marion and mouse-free Prince Edward Islands represent ideal ecosystems for addressing questions relating to the partitioning of potential influences of anthropogenic changes, such as climate change and alien species on ecosystem functioning. Consequently, weevil species were used in the present investigation to address questions of morphological change over time with reference to climate change and mous...
Abstract: Xylose is an unusual nectar sugar found in the nectar of Protea and Faurea (Proteaceae). Since nectar composition is an important floral characteristic in plant strategies for ensuring reproductive success, the unexplained presence of xylose in Protea nectar prompted this study of the interaction between pollinators and Protea species. Among pollinators that visit Proteaflowers in the south-western Cape Floral Kingdom, South Africa, insects and birds show an aversion to, and are po...
Abstract: Please read the abstract in the section 00front of this document
Abstract: Group size affects individual and collective vigilance levels of prey species. As individual vigilance decreases with increasing group size, the indirect risk of predation to each individual and the group as a whole will also decrease (dilution and many-eyes effect) which may have a decreasing effect on stress responses on group level as well. Where predation risk is low, other factors like group size might influence stress-related glucocorticoid output in prey species. I test the ...
Abstract: Water balance in insects is under neuroendocrine control, and both diuretic and antidiuretic factors are thought to be involved. Despite being the largest and most diverse order of insects, the Coleoptera have been largely neglected in studies of hormonal control of excretion. However, the only insect from which both diuretic and antidiuretic peptides, acting on Malpighian tubules, have been isolated, is a beetle: the mealworm Tenebrio molitor. This study reports the effects of dif...
Abstract: Genetic variation, structure and dispersal among Cape buffalo populations from the Hluhluwe-Imfolozi and Kruger National Parks of South Africa Barend Jacobus (Ben) Greyling Doctor of Philosophy (Zoology) Department of Zoology and Entomology Supervisor: Prof. Armanda Slager-Bastos Co-supervisor: Dr. Pim van Hooft 2007 The research reported on in this thesis is aimed at quantifying and qualifying, using a molecular genetics approach, some of the factors that influence the population ...
Abstract: Please read the abstract in the section 00front of this document.
Abstract: Sweetpotato, Ipomoea batatas (L.) Lamarck was introduced into Lesotho in 1992 in the hope that it would help alleviate poverty levels. Efforts are being made to learn the potential constraints to optimal production of this crop. Insect pests especially the sweetpotato weevils, Cylas species are a major production constraint worldwide. Hence the main objective of the study was to predict if these pests have potential to establish themselves in Lesotho. Two Cylas species, C. formicar...
Abstract: Please read the abstract in the section 00front of this document
Abstract: Sexual selection is a frame of reference that attempts to explain exaggerated signaling traits, including acoustic signals between male and female animals. Contemporary studies in the field of sexual selection are focused on the evolution of female mating preferences, with particular emphasis being placed on the good genes models of sexual selection. Here I investigate whether sexual selection is in operation in the acoustic communication system of the field cricket, Gryllus bimacu...
Abstract: African mole-rats (Bathyergidae) exhibit a wide range of social structures ranging from solitary to eusocial. This allows for studies looking at links between sociality and measurable characteristics such as spatial learning and kin-recognition. Furthermore, the existence of species with differing level of sociality allows for comparison between the highly social species and the solitary species. The existence of differences in spatial learning ability and memory between the sexes ...
Abstract: Instability characterizes the taxonomy of the African rodent subfamily Otomyinae. Two genera, Otomys and Parotomys, and 14 species are currently recognized, but the generic subdivision is equivocal. Between two and five cytotypes are delimited within O. irroratus, which illustrate a rapid rate of karyotypic evolution, and may reflect incipient speciation. In an attempt to resolve the group's phylogeny, the mitochondrial cyt b (complete) and 12S rRNA (802 bp) genes were analyzed usi...
Abstract: Please read the abstract in the section 00front of this document
Abstract: Please read the abstract in the section 00front of this document
Abstract: The demography of two elephant seal populations was examined and compared. This was done to investigate the reasons for the observed decreases in populations at Marion and Macquarie islands. While a well-established demographic programme had been in place at Marion Island since the 1980's (see Pistorius et al. (l999a) for a review) one had to be established at Macquarie Island. A long-term demographic programme was initiated at Macquarie Island in 1993 and hot brands were used to m...