Browsing by Author "Daniels, Ryan Joseph"

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    Dispersal and gene flow in the Southern African endemic Lacertid, Pedioplanis lineoocellata, based on microsatellite and capture-mark-recapture data
    (Stellenbosch : Stellenbosch University, 2014-12) Daniels, Ryan Joseph; Tolley, Krystal; Clusella-Trullas, Susana; Altwegg, Res; Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology.
    ENGLISH ABSTRACT: Dispersal determines connectivity between populations within a species and is a regulator of genetic differentiation through gene flow. Although the necessity of dispersal for gene flow is clear, for many taxa the relationship between the two is not well understood. Gene flow, or a restriction thereof, may be inferred from population-level genetic divergence estimates. These measures are averages of contemporary and historic gene flow and as such they are not necessarily easily compared to measures of real-time dispersal. Changes in dispersal have been inferred from present day spatial genetic structure for many southern African taxa and further associated with environmental change events. Pedioplanis lineoocellata is a southern African endemic lacertid with a mitochondrial DNA structure that may have been the result of Plio-Pleistocene glacial climatic oscillations. As a wide-spread, open habitat species, P. lineoocellata is an excellent study species for examining the relationship between dispersal and gene flow. In the first data chapter, Chapter 2, nine new microsatellite markers are described for several populations for the purpose of examining gene flow and genetic structure in the species. The possibility of null alleles, population bottlenecks and high inbreeding are investigated as possible explanations for the detected deviation from Hardy-Weinberg equilibrium (HWE). The presence of null alleles and, at one population, relatively high inbreeding best explains the HWE deviations. While null allele frequencies were not excessively high, this caveat should be borne in mind when interpreting results. In Chapter 3 the microsatellite markers were used to assess the geographic genetic patterns for P. lineoocellata across the distribution of the two most wide-spread mitochondrial lineages and to test for evidence of hybridization at a point of clade contact in the Loeriesfontein area. Microsatellite genetic clusters did not match the mtDNA lineages, a possible result of gene flow between clades. However, measures of genetic differentiation and recent migration indicate only weak contemporary long distance gene flow. There was no evidence of genetic admixture at the Loeriesfontein area despite sympatric mtDNA lineages. The complexity of the geographic arrangement of the microsatellite clusters may be attributed to historic range contraction and expansion events for the species. In the last data chapter, evidence for an isolation-by-distance (IBD) pattern was examined within the most widespread mtDNA clade. Sampling over hundreds of kilometres produced an IBD pattern when using spatial autocorrelation while failure to detect IBD using the Mantel test was likely a result of the complex arrangement of microsatellite clusters. A combination of genetic data and demographic data was used to estimate the annual dispersal distances based on the neighbourhood size concept. Results indicated high levels of dispersal that covered distances of a few hundred metres, greater than is expected for a lacertid lizard. Strong dispersal propensity would have influenced gene flow and genetic structure found in this thesis and will further influence future responses to environmental changes for the species.