Abstract
The vast majority of species are characterised by some form of special genetic structure across their ranges. These genetic patterns arise as a result of gene flow restrictions between populations due to barriers (such as geographical barriers, climate or habitat specificity). The biology, life history as well as habitat requirement of a species determines whether a barrier will be effective or not e.g. the Knersvlakte being an effective barrier to saxicolous species. Invasive species on the other hand are recently introduced species into new habitats. These species are often adaptive in nature as well as often closely associated with humans. Within this study, we aim to determine the genetic structure of two native species (a generalist species, the pouched mouse Saccostomus campestris, and a specialist species, the Eastern rock elephant shrew Elephantulus myurus) to determine how habitat connectivity influences the genetic patterns of comparable species. By using existing data, we will then analyse the genetic structure of an invasive species (the black rat, Rattus rattus) within two countries, The Democratic Republic of the Congo (DRC) (data obtained from Kaleme et al., 2011), and South Africa (data obtained from Bastos et al., 2011). Mitochondrial DNA was used to determine the genetic structure of all 3 species (the control region was used for both native species and the dataset from the DRC while cytochrome b was used for the invasives from South Africa). Bayesian trees as well as haplotype networks were constructed for all three species and an AMOVA was used to calculate standard Φ-statistics. All species were significantly structured, but the invasive species showed higher structure than the native species. Habitat connectivity was not the major driving forces behind the genetic structure observed within the native species. Instead we identified behaviour and possibly taxon-specific mutational rate as the likely factors responsible for the genetic structures observed. The dataset for the DRC consisted of two genetic groupings while the dataset for South Africa had three genetic groupings. This was the result of multiple introductions along independent introductory pathways, which mainly correspond to trade routes. Anthropogenic aided long distance dispersal is responsible for the large distances the species covers while intraspecific aggression enhances the introductory circumstance of the invasive species. The genetic structure observed in the two native species is a result of the interaction of the species with the natural habitat as well as behaviour and the taxon-specific mutational rate. In contrast, the invasive species’ genetic patterns reflect the different trade routes and introductory circumstance.
M.Sc. (Zoology)