Includes bibliographical references. / The collection of gall-forming Cecidomyiidae specimens and their parasitoids from Australia and South Africa during this project produced a large and valuable assemblage of material, most of which will be or has been lodged with the National Insect Collection (Pretoria) (parasitoids) or the South Australian Museum Adelaide (cecidomyiids).

Includes bibliographical references (leaves 161-202). / How predators affect the behaviour of their prey is one of the most studied subjects in behavioural ecology, with many hypothesis and models explaining how animals should behave and even more descriptive studies detailing how they do. The unification of the empirical with the theoretical, however, remains limited. The overall aim of my thesis was to address this paucity at Seal Island, South Africa, where recently quantified patterns of predation pressure by white sharks Carcharodon carcharias on Cape fur seals Arctocephalus pusillus pusillus suggested a landscape of fear particularly apposite to this.

Includes abstract. / Includes bibliographical references (p. 149-171). / This study aims to explore the relationships between river flow and fish ecology in the context of the riverscape model of river ecosystems by examining the seasonal distribution of two endangered fish species, i.e. the Clanwilliam yellowfish and Clanwilliam sawfin, in relation to their physical (structural) and hydraulic habitat requirements at several scales, and to assess the importance temporal changes in flow and temperature in relation to the timing of key life history events and recruitment. From these findings it aims to recommend water management strategies to ensure the persistence of remaining populations, as well as to suggest a way forward for fish habitat studies in South Africa. The study was conducted on the Driehoeks River, a tributary of the Doring River system, which rises in the Cederberg mountains of the Western Cape, South Africa. A 5.9 km segment of this river was selected for the study.

Includes abstract. / Includes bibliographical references. / In 2001, Dasineura dielsi (Diptera: Cecidomyiidae), a gall midge, was introduced into South Africa as a biological control agent on the invasive alien plant species, Acacia cyclops (Mimosaceae). An investigation was launched to test the following hypotheses: 1) the midges respond to the scent of A. cyclops to locate suitable oviposition sites; 2) the floral scent of A. melanoxylon, A. longifolia and A. saligna resembles that of A. cyclops and this explains the insects’use of these plants too; and 3) the floral scents of African acacias are distinctly different from A. cyclops and therefore has no attraction for D. dielsi.

Bibliography: pages 251-277. / In three digestion trials the energy intake and assimilation of the hyrax Procavia capensis was evaluated. Energy intake was low but the efficiency of energy assimilation was within the range found for other herbivores.

Bibliography: pages 162-175. / The south-western Cape is currently responsible for 45% of the total annual trout production in South Africa and further expansion of this industry in the region is likely. A pilot study of seven trout farms situated on the upper reaches of rivers in the south-western Cape was undertaken to determine whether there was a common trend in their effect on the rivers. Results indicated that the impact of the farms on the benthic invertebrate communities of the rivers ranged from mild to severe, based on the degree of change in the structure of the communities form upstream to downstream of the effluent outlets. Those farms situated on mountain streams had the greatest impact and those on the downstream foothill had a lesser impact. The reduced impact in the foothill zone was probably because these reaches were already disturbed by other catchment activities. Of the three farms that were situated on mountain streams and source areas, two used plastic portapools and the third earth dams. There was a substantial increase in the number of oligochaetes downstream of both 'portapool' farms and yet, despite being situated in the same sensitive river zone, this did not occur downstream of the farm that used earth dams. The general impact of trout farm effluent on the mountain-stream and source zones was to eliminate or greatly reduce the number of Limnichidae, Helodidae, Plecoptera, Elmidae, Heptageniidae and Ephemerellidae, and, in the case of portapool farms, to replace these with Naididae, Lumbriculidae, Chironomidae and Planaria. Once-off chemical samples were also collected at each site and, acknowledging the limitations of the sampling strategy, results showed that the particulate fraction of the effluent was probably responsible for the recorded reaction of the biota.

No description available.

Includes abstract. / Includes bibliographical references. / In this study, the systematics of the group is thus reviewed in its entirety for the first time in 74 years. Historical distributional data were gathered from the Iziko South African Museum (SAM) records, as well as from the uncatalogued wet collection, and from previously published literature. Photographic records submitted by SCUBA divers, and specimens collected during the course of this study provided more recent data.

Includes bibliographical references (p. 143-171). / This thesis addresses the recruitment patterns of barnacles and mussels at a range of spatial and temporal scales and attempts to relate them to larval and adult abundance, as well as to local productivity and oceanographic conditions that would influence larval transport and the connectivity of adult populations.

Bibliography: leaves 164-172. / Nectarivores feed on aqueous sugar solutions, and their water balance is tightly linked to their energy balance. When nectar is dilute and energy demands are high, consumption of a large excess of preformed water is inevitable. Physiological implications of nectarivory for the lesser double-collared sunbird, Nectarinia chalybea, have been investigated here. Sunbirds consumed 2.7 times their body mass (8 g) per day when feeding on 0.4 M sucrose at an ambient temperature of 10°C, and excreted 87 % of the water. When feeding on 1.2 M sucrose at 30°C, sunbirds drank only 0.5 times their body mass of water daily. In view of the sometimes high flux of water, combined with the low electrolyte concentrations of nectar, sunbirds must be efficient at conserving ions to maintainelectrolyte balance. When 15 mM each of KCl and NaCI were included in a diet of 0.4 M sucrose, sunbirds precisely maintained electrolyte balance by increasing cation excretion from 2 to 17 mM. Considering the high preformed water content of dilute nectar, sunbirds may expend large amounts of energy warming their food to body temperature, which was measured as 42°C irrespective of diet. Modelling revealed that sunbirds feeding on dilute (0.4 M) sucrose at 18°C would use the same proportion of their daily energy intake (4 %) to warm their food as high-latitude aquatic endotherms feeding on fish or invertebrates just above freezing point. The evaporative water loss (and therefore evaporative heat loss) of N. chalybea increased as dietary sucrose concentration decreased (more than two-fold between 1.2 and 0.2 M).