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

[摘要] ENGLISH ABSTRACT: The comparative phylogeography of the host-parasite relationship of the southern Africanendemic dark shyshark, Haploblepharus pictus and its nematode parasite, Proleptusobtusus was investigated. To date, no studies have been conducted on the populationstructure of catsharks and their species specific parasites and little is known about thepopulation dynamics of these species. A total of 116 catsharks and 201 parasites wereanalysed from seven South African localities. The mitochondrial marker COI was usedand species specific primers were designed for both the host and parasite. Haplotypenetworks were constructed and no strong geographically structured groupings were foundfor either species. Pairwisest values for the parasite and host found Gansbaai to besignificantly differentiated from the other sites. Fu's Fs were significantly negative for bothhost and parasite indicating population disequilibrium. Proleptus obtusus displayed apattern of population expansion which was confirmed by the mismatch distribution.Mismatch distributions failed to indicate population expansion for the sharks. Other factorssuch as selection, migration or genetic drift are likely the cause of the populationdisequilibrium detected. Interestingly, no barrier to gene flow was found around CapePoint, a known break for other species such as the clinid, Clinus cottoides and thecaridean shrimp Palaemon peringueyi. The outcome of this study suggests that levels ofgene flow in H. pictus are high enough to suggest that the documented site fidelity is notas strong as originally proposed. The parasite, being dependent on the host, shows asimilarly high level of gene flow among sampling sites.

[发布机构] Stellenbosch University