Abstract: Patterns of invertebrate species richness and body size across elevational gradients have been well-documented in a variety of studies. However, very little is known about the factors that govern these patterns along elevational gradients. A number of studies have have reported a monotonic decrease in species richness with increasing elevation; while others have observed a hump-shaped pattern, where the peak of species richness occurs at an intermediate elevation. For body size, st...
Abstract: Winged Rhopalosiphum padi in search of good quality host plants transmit the non-persistent Potato virus Y (PVY) to seed potatoes. Planting a non-virus host plant as a border around the main crop can reduce PVY incidence, because aphids tend to land in high numbers at the edge of a field and the crop border acts as a virus sink. Using a trap crop could increase the number of aphids landing in the border. During host-plant searching behaviour, alate (winged) aphids respond to short ...
Abstract: Mining activities greatly contribute to economic growth and development in South Africa. However, post-mining soils have limited land-use potential due to low fertility, deficiency in organic matter content and poor physical, chemical, and microbiological properties. Mechanical methods to improve soil conditions, such as ripping, are expensive and provide temporary improvements. Alternatively, exploring biological methods could aid in creating arable land from degraded soils, where...
Abstract: The reproductive biology of spotted hyaenas was studied from a sample of 39 females and 36 males collected in game reserves in south~rn Africa. A method for age estimation, based on the relative attrition of PM2 was developed. Female spotted hyaenas attain sexual maturity at three years of age, are polyoestrus with recurring oestrous cycles throughout the lactation period. Females were still reproducing when 16 years old. Breeding was not restricted to a particular season, as bi...
Abstract: The presence of huge quantities of nutrients in water bodies heavily promotes the growth of algae. Excess nitrogen and phosphorus in discharged wastewaters can lead to downstream eutrophication thereby damaging the ecosystem. Algae bioremediation involves the use of live algae in the removal of excess dissolved nutrients from wastewater and subsequently diminish the pollution load. It is an alternative economical and sustainable way of treating sewage wastewater compared to convent...
Abstract: Please read the abstract in the dissertation
Abstract: The flightless Cape High-mountain stag beetle genus Colophon (Coleoptera: Lucanidae) is studied. Represented by 17 species, which are restricted to the highest mountain peaks of the Cape Floristic Region in the Western Cape, South Africa, and show a strict association with the fynbos biome. The study aimed to determine the specific and phylogenetic status of the described species of Colophon and to determine the main factors driving their evolution by testing hypotheses of relation...
Abstract: There has been a widespread assessment of the capacity of grasslands to restore after several forms of disturbance. In South Africa forestry is a significant habitat disturbance within the Eastern Highveld grasslands where this study was conducted. The study compared ant communities between disturbed grasslands that have been rehabilitated after pine forestry and undisturbed grasslands. Ant sampling was conducted using pitfall traps within rehabilitated sites of age 10 years to 40 ...
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: Investigating the extent of local scale heterogeneity in assemblages is necessary to achieve a sound understanding of the processes giving rise to local assemblage patterns and the variation between them. Moreover, a clear understanding of local scale heterogeneity of assemblages is imperative in the development of effective regional conservation strategies. Previous studies examined the local scale heterogeneity in dung beetle assemblages between mixed woodland and sand forest hab...
Abstract: When provided with the opportunity to select their diet, most insect herbivores regulate their nutrient intake. However, in a nutritionally heterogeneous environment and with changing demands for growth, development and reproduction, obtaining the required amount and balance of nutrients is a challenge. This is especially true for social insects where the workers bring food into the colony to be shared by nestmates. The ability of insects to self-select their diet is an important t...
Abstract: Please read the abstract in the front section of this document
Abstract: Pollination is an essential ecosystem service, increasing reproductive success of many crops, which can be provided by managed pollinators, wild bees (including honeybees) and other insect pollinators. However, the pollination services and the economic value of wild pollinators are often underestimated. Better understanding of the factors that influence honeybee foraging behaviour and pollination efficiency can contribute to the improvement of management practices that aim to enhan...
Abstract: One of the benefits of colonial living in insect societies is the ability to build a nest which enables the maintenance of a homeostatic microenvironment. The detrimental and uncertain effects of fluctuating ambient conditions are thus avoided. An extensive amount of work has documented the regulation of respiratory gases and temperature by honeybee (Apis mellifera) colonies but relatively little is known of their water relations. Nest humidity influences the fitness of the honeybe...