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A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 3 May 2018. / The movement ecology of a species can dictate their survival and success. Animals are motivated to move depending on resource priorities and in turn their movements are influenced by the surrounding environment. Natural habitats are being increasingly disturbed by anthropogenic changes which often creates several implications for the existing wildlife. One of these changes include extensive road networks that may fragment landscapes and increase mortality risks for local fauna. This current and global issue is often researched with the aid of road kill statistics which can create a biased view. My study highlights a more realistic method for understanding how organisms interpret and react to road infrastructure by using the movement patterns of 109 telemetered Puff Adders (Bitis arietans). To assess the effect of roads on these snakes within Dinokeng Game Reserve (Gauteng, South Africa) over eight years, Puff Adder lie-up locations (to the nearest road) and movement paths were analysed. Sex, season, years, and the types of roads within the reserve were included to evaluate the motivation for movement and if roads were inhibiting or aiding movement patterns. Compared to random, Puff Adders were closer too, and crossed roads more often. Males crossed roads more frequently than females and during non-mating season, both sexes were closer to roads. Narrow roads with low levels of traffic were also crossed more often. Overall, the roads in Dinokeng Game Reserve do not inhibit movement and patterns suggest that roads may be advantageous for Puff Adders. Roads appear to be foraging hotspots because of micro habitats created along the verges. However, these positive attributes could result in a potential risk when road usage is intensified by traffic. Understanding how species interact with changes to their environment is essential for appropriate management and mitigation and this study illustrates the necessity for unbiased research to properly evaluate these changes and reactions. / EM2018

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Masters of Science, Johannesburg 2018 / The morphology and functionality of surface microornamentation in southern African snakes is well-established in terms of resulting optical effects. Velvet-blackness, a type of optical effect is produced when light incident on a scale is scattered by microornamentation. I tested microornamentation from Bitis arietans dorsal exuvia for these optical effects. Scales were excised from shed skins of B. arietans and sputter coated with 15 nm Gold-Palladium to control the effect of pigment. Spectral intensity (SI) of three scale regions of known micro topography was recorded using spectrophotometry over the visible spectrum only as a measure of reflectivity of the scales. Given that surface roughness (the deviation of a membrane’s surface topography from an ideal surface) is a product of the size of surface asperities and its degree of randomness, the three scale regions in order of decreasing surface roughness were dark (dorsal) scales, pale (dorsal) scales, and ventral scales. Measures of SI on dorsal and ventral scale regions revealed lowest SI on dark dorsal scales and highest on ventral scales. In general, the level of micro-structuring was inversely proportional to SI. To test if optical effects are angle-dependent, I measured differences in SI between normal (90) and oblique (45) angles of incidence. Differences in SI between 90 and 45 were significant for all scale regions which revealed that while microornamentation produces optical effects at both normal and oblique incidence, the effect is greater at 45. Given that SI varies with surface roughness such that dark scales have a lower SI than pale scales, I conclude that scale colour in B. arietans is a product of optical effects created by microornamentation. The optical effect may improve the visual camouflage of B. arietans during ambush. While microornamentation is best known for its optical effects, it may have other functions. I examined the microornamentation in Bitis schneideri (Namaqua Dwarf Adder) using electron microscopy and found small, tooth-like protuberances distributed uniformly across the scales and across all body regions. I measured the distance between adjacent denticles which I 5 compared to the mean dimensions of sand grains from two study sites: Noup, within the distribution of B. schneideri, and Tswalu, outside of it but with significantly smaller grains. The space between denticles is smaller than sand grains from both sites. Due to its physical characteristics, microornamentation in B. schneideri has the potential to restrict sand grains from direct contact with the scale surface. These results suggest that microornamentation can function to shield the integument from sand abrasion in B. schneideri. This study demonstrates specific functions of microornamentation in the ecology of two species of Bitis. / XL2019

Population genetic structure is widespread in many organisms and can be found at small spatial scales. Fine-scale differentiation is the result of ecological and evolutionary processes working together to produce an overall pattern, but the relative importance of these factors in population differentiation is poorly understood. The goals of my research were to describe patterns of population genetic differentiation and to identify ecological and evolutionary factors important for population divergence. To this end, I investigated several aspects of genetic differentiation for three vertebrates in northern California. The focal species were the terrestrial garter snake (Thamnophis elegans) and the common garter snake (Thamnophis sirtalis) that occupy a series of ponds, lakes and flooded meadows in northern California. I found significant genetic differentiation and isolation by distance, as well as correlated patterns of pairwise divergence in both species. Independent estimates of effective population size and bi-directional migration rates also uncovered source-sink dynamics in both species that suggest frequent extinction-recolonization events within a metapopulation context. The generality of source-sink dynamics for an ecologically similar species within the same ecosystem was explored using a third species, B. boreas. I also identified ecological correlates of several population genetic parameters for all three species. Although F[subscript ST] were similar, B. boreas had larger effective population sizes, lower migration rates, lacked source-sink dynamics, and appeared to be in migration-drift equilibrium, indicative of a temporally stable population structure. A clustering analysis identified a series of block faults as a common barrier to dispersal for both garter snakes, and ecological correlates were found to be more similar among response variables than within species. I then compared degree of genetic differentiation at quantitative traits with that at neutral markers to infer strength of selection and adaptive divergence between two ecotypes of T. elegans. Selection on most traits was relatively weak, but strong diversifying selection was found for background coloration, total number of ventral scales and number of infralabials. Overall, my research documented ecological and evolutionary processes associated with population differentiation in a metacommunity and respresents an important contribution toward the unification of ecology and evolutionary biology. / Graduation date: 2005