Thesis (DPhil)--University of Stellenbosch, 2008. / ENGLISH ABSTRACT: Sub-Antarctic islands represent the only mid to high latitude terrestrial biomes in the Southern Hemisphere. These
islands have various geological origins and histories, well-preserved terrestrial ecosystems and high levels of
species endemism. In an attempt to understand the evolution and biogeography of terrestrial taxa in the South
Polar Region, the first broad-scale molecular phylogeny was constructed for the unique terrestrial group, the
ameronothroid mites (genus Halozetes (Oribatida)), collected from sub-Antarctic and Maritime Antarctic localities.
Phylogenetic analyses based on a combined mitochondrial (cytochrome oxidase subunit I (COI)) and nuclear
(histone-3 (H3)) sequence dataset indicated that the evolution of these mites were habitat specific (i.e. intertidal,
supralittoral and terrestrial). Notwithstanding criticisms levelled against a molecular clock, the mites were
evolutionary young (<10myo), contrary to their status as an ancient group predating Gondwana fragmentation.
Biogeographic analyses indicated a complex pattern mainly sculpted by multiple independent dispersal events
across the Antarctic Polar Frontal Zone similar to previous findings for other marine and terrestrial taxa. Also, the
molecular phylogeny displayed considerable discourse with contemporary taxonomy suggesting the need for
taxonomic revisions and reassessment of morphological characters. Sub-Antarctic Marion Island, the larger of the
two islands comprising the Prince Edward Island archipelago (PEI), has experienced extensive glaciation and
volcanism. To assess the impact of historical events (volcanism (including recent eruptions) and glaciation) and
contemporary mechanisms (gene flow) on the genetic spatial distribution of species from Marion Island, two mite
species namely Eupodes minutus (Prostigmata) and Halozetes fulvus (Oribatida) as well as a single plant species,
Azorella selago (Apiaceae), were selected as model organisms. For independent phylogeographic analyses,
mitochondrial sequence data (COI) were obtained for both mite species, while chloroplast sequence (trnH-psbA)
and amplified fragment length polymorphism (AFLP) data were generated for the cushion plant, A. selago. Since
A. selago is typified by two growth forms namely discrete cushions and continuous mats, it was essential to
examine the growth dynamics prior to phylogeographic analyses. The sequence and fragment data indicated that
both mite and plant species were significantly substructured across Marion Island. Manual comparisons indicated
unique populations on the western (Kaalkoppie for H. fulvus, La Grange Kop for E. minutus and Mixed Pickle for
A. selago), eastern (Bullard Beach for H. fulvus and Kildalkey Bay for E. minutus), northern (Middelman and Long
Ridge for H. fulvus) and southern side (Grey Headed for H. fulvus and Watertunnel for A. selago) of the island.
Importantly, the western side had unique localities for all species. Interestingly, based on the H. fulvus data, the
western populations were relatively young, characterized by high migration rates, small effective (female)
population sizes with no isolation-by-distance. The opposite scenario was found for the eastern populations. This
spatial genetic structure described for species on Marion Island can be ascribed to both historical events and
environmental conditions. These areas with their unique genetic composition are of special conservational
concern; consequently this research will contribute to an active management plan for PEI, South Africa’s only
Special Nature Reserve. / AFRIKAANSE OPSOMMING: Sub-Antarktiese eilande verteenwoordig die enigste terrestriële bioom in die middel tot hoër breedtegrades van
die Suidelike Halfrond. Hierdie eilande besit ‘n verskeidenheid van geologiese oorspronge en geskiedenisse,
goed-bewaarde terrestriële ekosisteme en hoë vlakke van endemisme. In ‘n poging om die evolusie en
biogeografie van terrestriële taksa in die Suid Pool Area te verstaan, is die eerste grootskaalse molekulêre
filogenie saamgestel vir ‘n unieke terrestriële groep, die ameronothoïed miete (genus Halozetes (Oribatida:
Ameronothroidea)), vanaf menigte sub-Antarktiese en Maritime Antarktiese lokaliteite. Filogenetiese analises
gebaseer op die saamgestelde mitochondriale (sitokroom oksidase subeenheid I (COI)) en nukluêre (histoon-3
(H3)) basispaarvolgordes het aangedui dat die evolusie van hierdie miete habitat spesifiek is (m.a.w inter-gety,
supralitoraal en terrestrieël). Ongeag die kritiek teenoor ‘n molekulêre klok, is hierdie miete evolusionêr jonk
(<10mjo), wat teenstrydig is met hulle status as ‘n antieke groep wat terugdateer voor Gondwana fragmentasie.
Biogeografiese analises het ‘n komplekse patroon aangedui wat grotendeels gekarakteriseer word deur menigte
onafhanklike verspreidingsgebeurtenisse bo-oor die Antarktiese Polêre Frontale Zone, wat ooreenstemmend is
met vorige bevindinge vir ander mariene en terrestriële taksa. Die molekulêre filogenie het ook aansienlik verskil
van die tradisionele taksonomie, dus is taksonomiese aanpassings en herklassifisering van morfologiese
karakters noodsaaklik. Sub-Antarktiese Marion Eiland, die groter eiland van die Prins Edward eilandgroep (PEI),
het uitermate glasiasie en vulkanisme ondervind. Om die impak van historiese gebeurtenisse (vulkanisme
(insluitend onlangse uitbarstings) en glasiasie) en kontemporêre meganismes (geenvloei) op die genetiesgespasieërde
verspreiding van spesies vanaf Marion Eiland te bepaal, was twee mietspesies naamlik Eupodes
minutus (Prostigmata) en Halozetes fulvus (Oribatida) asook ‘n enkele plantspesie, Azorella selago (Apiaceae),
gekies as model organismes. Vir onafhanklike filogeografiese analises, was die mitochondriale basispaarvolgorde
(COI) vir beide mietspesies bepaal, terwyl chloroplast basispaarvolgorde (trnH-psbA) asook geamplifiseerde
fragmentlengte polimorfisme (AFLP) data gegenereer was vir die kussingplant, A. selago. Aangesien A. selago
gekenmerk word deur twee groeivorme, naamlik diskrete kussings en aaneenlopende matte, was dit noodsaaklik
om eers die groeidinamika van die plant te ondersoek alvorens ‘n filogeografiese studie kon geskied. Die
basispaarvolgordebepalings en fragmentdata het aangedui dat beide mietspesies sowel as die plantspesie
betekenisvolle substruktuur vertoon regoor Marion Eiland. Informele vergelykings het unieke populasies aangedui
op die westelike (Kaalkoppie vir H. fulvus, La Grange Kop vir E. minutus en Mixed Pickle vir A. selago), oostelike
(Bullardstrand vir H. fulvus en Kildalkeybaai vir E. minutus), noordelike (Middelman en Long Ridge vir H. fulvus) en
suidelike kant (Grey Headed vir H. fulvus en Watertunnel vir A. selago) van die eiland. Die westelike kant besit
dus unieke lokaliteite vir al die spesies. Interressantheidhalwe het die H. fulvus data getoon dat die westelike
populasies relatief jonk is en gekarakteriseer word deur hoë migrasiesyfers en klein effektiewe (vroulike)
populasiegroottes met geen isolasie-oor-afstand nie. Die resultate vir die populasies aan die oostelike kant van die
Marion Eiland was presies teenoorgesteld. Dié beskryfde substruktuur vir die spesies op Marion Eiland is
afkomstig van beide historiese gebeurtenisse asook omgewingstoestande. Hierdie areas met hul unieke genetiese samestelling, is belangrik vir natuurbewaring. Hierdie navorsing sal bydra tot die bestuursriglyne van PEI, Suid
Afrika se enigste Spesiale Natuurreservaat.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/21744 |
| Date | 03 1900 |
| Creators | Mortimer, Elizabeth |
| Contributors | Jansen Van Vuuren, Bettine, Daniels, Savel R., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | xiv, 107 leaves : ill., maps |
| Rights | Stellenbosch University |
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