Comparative phylogeography of the catshark, Haploblepharus pictus and its nematode parasite, Proleptus obtusus

McLachlan, Ann (2011-12)

Thesis (MSc (Botany and Zoology))--Stellenbosch University, 2011.

Thesis

ENGLISH ABSTRACT: The comparative phylogeography of the host-parasite relationship of the southern African endemic dark shyshark, Haploblepharus pictus and its nematode parasite, Proleptus obtusus was investigated. To date, no studies have been conducted on the population structure of catsharks and their species specific parasites and little is known about the population dynamics of these species. A total of 116 catsharks and 201 parasites were analysed from seven South African localities. The mitochondrial marker COI was used and species specific primers were designed for both the host and parasite. Haplotype networks were constructed and no strong geographically structured groupings were found for either species. Pairwise st values for the parasite and host found Gansbaai to be significantly differentiated from the other sites. Fu’s Fs were significantly negative for both host and parasite indicating population disequilibrium. Proleptus obtusus displayed a pattern of population expansion which was confirmed by the mismatch distribution. Mismatch distributions failed to indicate population expansion for the sharks. Other factors such as selection, migration or genetic drift are likely the cause of the population disequilibrium detected. Interestingly, no barrier to gene flow was found around Cape Point, a known break for other species such as the clinid, Clinus cottoides and the caridean shrimp Palaemon peringueyi. The outcome of this study suggests that levels of gene flow in H. pictus are high enough to suggest that the documented site fidelity is not as strong as originally proposed. The parasite, being dependent on the host, shows a similarly high level of gene flow among sampling sites.

AFRIKAANSE OPSOMMING: Die vergelykende filogeografie van die gasheer-parasiet verhouding tussen die endemiese suider-Afrikaanse donker skaamhaai, Haploblepharus pictus en sy nematode parasiet, Proleptus obtusus is ondersoek. Huidiglik is daar nog geen ander studies uitgevoer met betrekking tot die populasie struktuur van skaamhaaie en hul spesies-spesefieke parasiete nie en min is bekend oor die populasie dinamiek van hierdie spesies. In hierdies studie is ‘n totaal van 116 skaamhaaie en 201 parasiete vanaf sewe lokaliteite geanaliseer. Die mitikondriale merker COI is hiervoor gebruik en spesie spesefieke inleiers is vir beide gasheer en parasiet ontwerp. Haplotipe netwerke is saamgestel vir beide spesies en het geen duidelike geografies gestruktureerde groepe aangedui nie. Paarsgewyse st waardes van beide parasiet en gasheer het daarop gedui dat Gansbaai geneties gedifferensieerd is van alle ander lokaliteite. Fu se Fs was statisties betekenisvol met ‘n negatiewe waarde vir beide spesies, wat dui op populasie disekwilibrium. Proleptus obtusus het ‘n patroon van populasie groei getoon, wat deur Fu se Fs en die misparing verspreiding bevestig is. Die misparing verspreiding het nie populasie toename vir die skaamhaaie aangedui nie. Die waargeneemde populasie disekwilibrium is waarskynlik die gevolg van seleksie, migrasie of genetiese drywing. Geen genetiese breuk is by Kaap Punt, wat ‘n genetiese breuk vir verskeie ander spesies soos Clinus cottoides en Palaemon peringueyi is, gevind nie. Die uitkomstes van hierdie studie stel voor dat vlakke van geen vloei in H. picuts hoog genoeg is om ‘n patroon van genetiese vermenging tussen lokaliteite, op die mitokondriale DNS vlak, tot gevolg te hê. Dit beteken moontlik dat die gedokumenteerde gebied gebondenheid van hierdie spesie nie so sterk, soos oorspronklik voorgestel, is nie. Die parasiet, waarskynlik aangesien hy van sy gasheer afhanklik is, toon ‘n soortgelyke hoë vlak van geen vloei tussen lokaliteite. Dus toon beide spesies ‘n algehele afwesigheid van genetiese struktuur, met die isolasie van Gansbaai van alle ander lokaliteite.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/18106
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