Comparative phylogeographic patterns among selected indigenous and introduced Collembola on Marion Island

Myburgh, Marike (2006-04)

Thesis (MSc)--University of Stellenbosch, 2006.

Thesis

ENGLISH ABSTRACT: Marion Island is situated approximately 2600 km southeast of Cape Town and is the larger of the two islands that comprise the Prince Edward Island group. During past glaciation events, Marion was partially covered by ice with fauna and flora confined to isolated refugia across the island. As a result of these long-term isolation events, it is postulated that species predating these glaciation events might show geographic partitioning of genetic variation. Subsequently, the majority of Southern Oceanic islands have a history of sealing activities with vessels frequenting various islands in their hunt for seals. These combined visits to several islands could have facilitated the introduction of alien species, or the reintroduction of species already present on islands. These incidents, combined with more recent scientific voyages, have led to the establishment of several exotic species on Marion Island. Two indigenous Collembola species (Cryptopygus antarcticus (Willem, 1901) and Tullbergia bisetosa (Börner, 1903)) were chosen as model species to investigate the possible effects of glaciation on the spatial distribution of genetic variation on indigenous species. Given the negative impact that alien taxa have on indigenous species and ecosystems, the phylogeographic population structure of the recently introduced Isotomurus cf. palustris (Müller, 1876) was determined and compared to those described for the two indigenous species. To address these questions, two mitochondrial DNA genes were targeted: cytochrome oxidase subunit I (COI) and cytochrome oxidase subunit II (COII). These genes were sequenced (GENBANK accession numbers DQ147289-DQ147558) and analysed using, amongst others, AMOVA (Analysis of Molecular Variance), SAMOVA (Spatial Analysis of Molecular Variance) and NCA (Nested Clade Analysis). As expected, the two indigenous species showed distinct signs of population expansion, whilst the recently introduced species exhibits little genetic variance across its range. The life histories of species have an influence on their resultant genetic signature; therefore life history parameters were incorporated to explain differences in the phylogeographic patterns observed for these three species.

AFRIKAANSE OPSOMMING: Marion Eiland is die groter van twee eilande wat die Prins Edward eilandgroep vorm, ongeveer 2600 km suid-oos vanaf Kaapstad. Gedurende glasiasie episodes in die verlede, was Marion gedeeltelik met ys bedek en fauna en flora was geisoleer in klein gedeeltes van die eiland wat beskut was. As gevolg van hierdie langtermyn isolasie word daar voorgestel dat spesies wat op die eiland was voor hierdie gebeurtenisse plaasgevind het, ‘n geografiese verdeling van genetiese variasie sal toon. Sedertdien het die meerderheid van die eilande in die Suidelike Oseaan ook ‘n geskiedenis van skepe wat op een of meer van die eilande aangedoen het in die jag op robbe. Hierdie besoeke deur die robjagters aan die eilande het meegebring dat daar eksotiese spesies op die eiland aangekom het of dat spesies wat reeds op die eiland voorgekom het, opnuut daar geland het. Hierdie, tesame met die onlangse wetenskaplike reise na Marion Eiland, het daartoe gelei dat baie eksotiese spesies ingevoer is na die eiland. Twee inheemse spesies, naamlik Cryptopygus antarcticus (Willem, 1901) en Tullbergia bisetosa (Börner, 1903) is gekies om as model spesies te dien om die moontlike gevolge van glasiasie op die geografiese verspreiding van genetiese variasie te toets. In ag geneem die moontlike negatiewe impak wat eksotiese spesies op die inheemse spesies mag hê, is die filogeografie van ‘n uitheemse spesie, Isotomurus cf. palustris (Müller, 1876) ook bepaal en vergelyk met díe van die bogenoemde inheemse spesies. Dit is gedoen deur twee gene, sitokroom oksidase I (COI) en sitokroom oksidase II (COII) te analiseer. Hierdie gene se basispaarvolgordes is bepaal (GENBANK toetreenommers DQ147289-DQ147558), en hulle is ge-analiseer deur gebruik te maak van AMOVA (Analise van Molekulêre Variasie), SAMOVA (Ruimtelike Analises van Molekulêre Variasie) en NCA (geseteldegroepsanalises). Net soos verwag, het die twee inheemse spesies albei duidelike tekens getoon van ‘n bevolkingstoename terwyl die uitheemse spesie amper geen variasie oor sy verspreidingsgebied getoon het nie. Die lewensstyle van spesies het ‘n beduidende invloed op hulle genetiese bevolkingstruktuur. As sulks is díe in ag geneem om die verskille tussen hulle genetiese strukture te verduidelik.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/21686
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