Female reproductive philopatry and male-mediated gene flow in NSW Port Jackson sharks

Understanding genetic population structure and the reproductive ecology of marine species is becoming increasingly important when developing conservation plans, due to the anthropogenic threats now facing marine ecosystems and species. Population structure in Port Jackson Sharks, Heterodontus portusjacksoni, was investigated using ten polymorphic microsatellites and the mitochondrial DNA (mtDNA) control region (adults: n = 89; embryos: n = 75) from two locations in New South Wales (NSW) – Sydney (SYD) and Jervis Bay (JB). MtDNA diversity was moderately low and nuclear DNA diversity was intermediate for all NSW adults. Significant structure was detected between SYD and JB using mtDNA but not microsatellites. Mean AIc values were significantly higher for females compared to males in JB but not SYD. These results reveal population genetic substructure in NSW. Females and males migrate inshore during the austral winter for breeding, however only females exhibit reproductive philopatry. Therefore, it appears the males are facilitating gene flow between populations. This study did not detect fine-scale structure within JB, however further research focusing on localized structure is needed to accurately assess this. Philopatric behaviour in H. portusjacksoni means the breeding sites and mating behaviours of this species should be considered when developing conservation management strategies.