Environmental & Physical Sciences

Environmental & Physical Sciences Research Papers/Topics

The relative importance of natural and human-induced environmental conditions for species richness distribution patterns in South Africa

Abstract: I studied the spatial distribution of South African avian species richness from the viewpoint that humans are a substantial modifying force on earth, and have also modified the historical spatial distribution of species richness. The main aim of the thesis is to investigate the way in which humans have modified avian species richness patterns in South Africa at the quarter-degree square (QDS) resolution, which is a phenomenon that has been either overlooked, or not completely clari...

Implications of global change for important bird areas in South Africa

Abstract: The Important Bird Areas (IBAs) network of BirdLife International aims to identify sites that are essential for the long-term conservation of the world’s avifauna. A number of global change events have the potential to negatively affect, either directly or indirectly, most bird species, biodiversity in general and associated ecological processes in these areas identified as IBAs. To assist conservation decisions, I assessed a suite of ten landscape scale anthropogenic pressures t...

Regulation of protein and carbohydrate intake in caged honeybees Apis mellifera scutellata : assessment based on consumption and various performance measures

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...

Structure and function of a Lepidoptera assemblage in a human-influenced environment

Abstract: Please read the abstract in the front section of this document

Behavioural response of honeybees (Apis mellifera scutellata Lep.) to wild pollinators on sunflowers (Helianthus annuus L.)

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...

Homeostasis : humidity and water relations in honeybee colonies (Apis mellifera)

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...

Mechanisms and control of secretion in the Malpighian tubules of Tenebrio molitor : an immunohistochemical and electrophysiological study

Abstract: Fluid secretion by insect Malpighian tubules is controlled by haemolymph-bome factors. Two corticotropin-releasing-factor (CRF)-related diuretic peptides, Tenmo¬DH37 and Tenmo-DH47. previously isolated from Tenebrio molitor, were found to stimulate in vitro tubule preparations of Tenebrio molitor via the second messenger cyclic AMP. The stimulatory effect of Tenmo-DH37 was reversed on addition of endogenous antidiuretic peptides (Tenmo-ADFa and ADFb) and exogenous cardioaccelerato...

Digestion of maize and sunflower pollen by the spotted maize beetle Astylus atromaculatus (Melyridae)

Abstract: The relationship between beetles and flowers is often mutually beneficial. Flowers provide not only edible rewards and favourable micro-environments, but may also be sites for mating and egg-laying activities. Even though beetles consume various parts of flowers, including pollen, and can sometimes cause considerable damage, they are in fact important pollinators of many flowers. Pollen was once considered indigestible but is actually a highly nutritious food source for many animal...

Phylogeography of Scarabaeus (Pachysoma) Macleay (Scarabaeidae: Scarabaeinae)

Abstract: Scarabaeus (Pachysoma) consists of 13 flightless dung beetle species endemic to the arid west coast of southern Africa. Scarabaeus (Pachysoma) are unique in their feeding and foraging habits, in that they randomly search for dry dung/detritus which, when found, is dragged forwards, and buried in a pre-constructed holding chamber, as opposed to the convention of rolling it backwards. This action is repeated to provision the chamber after which the nest is expanded to below the moist...

Climate change and tick-host relationships in Africa

Abstract: Please read the abstract in the section 00front of this document

Tick-host interactions in Hyalomma species

Abstract: Please read the abstract in the section front of this document


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