Browsing by Author "Bester-van der Merwe A.E."

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    A population genetic analysis of abalone domestication events in South Africa: Implications for the management of the abalone resource
    (2012) Rhode, Clint; Hepple J.-A.; Jansen S.; Davis T.; Vervalle J.; Bester-van der Merwe A.E.; Roodt-Wilding R.
    Abalone culture is South Africa's largest aquaculture sector in terms of revenue. Nonetheless, the industry is in its formative years and much scope remains for refinement and regulation of production practices. It is important to manage genetic diversity in terms of the particular breeding objectives pursued by respective facilities: selective breeding vs. ranching; whilst conserving the genetic integrity of wild populations remains a national imperative. The present study found no significant decrease in genetic diversity between wild and cultured populations as based on heterozygosity and allelic content of genomic- and EST-microsatellite loci. However, estimates for pairwise genotypic differentiation, F st, AMOVA and Factorial correspondence analysis suggest the genetic heterogeneity of cultured populations and their significant differentiation from the wild progenitor populations. As expected, the cultured population showed reduced effective population sizes, but relatedness remained low. It is postulated that both neutral and selective evolutionary forces are responsible for the observed patterns of genetic variability within and amongst populations. The implications of the results are discussed in terms of broad managerial objectives for the South African abalone and continued monitoring is advised. © 2012 Elsevier B.V.
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    Molecular phylogeny of South African abalone, its origin and evolution as revealed by two genes
    (2012) Bester-van der Merwe A.E.; D'Amato M.E.; Swart B.L.; Roodt-Wilding R.
    The marine family Haliotidae (Mollusca: Gastropoda) includes approximately 56 extant abalone species found worldwide. None of these species are globally distributed while four areas of endemism (temperate Australia, South Africa, New Zealand and North Pacific) have been recognized. Phylogenetic relationships of 18 abalone species including five South African species were reconstructed using a combined data set containing sequence data of the mitochondrial NADH-dehydrogenase subunit 1 (ND1) gene and the nuclear hemocyanin gene. The molecular topologies confirmed former findings of two major abalone lineages with Northern and Southern Pacific distribution within the Haliotidae family. The phylogeny revealed all five South African species as a monophyletic group with a sister relationship to the Australian endemics clade. It further suggested a relatively recent radiation of the South African species and places it within the same evolutionary context as the Mediterranean/Atlantic and Australasian clades. Molecular phylogeny also revealed a split within the South African group as well as further speciation within one of the two subclades. Possible place of origin for South African abalone are discussed and ecological specialization, e.g. differential adaptation to environmental conditions, is proposed as the most likely scenario describing divergence within the South African clade. © 2012 Copyright Taylor and Francis Group, LLC.