Population genetic analyses reveal female reproductive philopatry in the oviparous Port Jackson shark

Abstract

Restricted gene flow and reproductive philopatry are increasingly being described in marine predators such as sharks. However, observing shark reproductive behaviour in situ is problematic because of issues associated with sampling in the marine environment. As such, molecular tools have become fundamental to unravelling complex mating behaviours. In this study, we examined patterns of genetic structure in the oviparous Port Jackson shark (Heterodontus portusjacksoni) using 10 microsatellite loci and the mitochondrial (mt)DNA control region. Patterns of genetic structure were investigated between breeding aggregations in Sydney and Jervis Bay, as well as between two sites within Jervis Bay. Significant genetic differentiation was detected between Sydney and Jervis Bay using mtDNA, but no structure was observed within Jervis Bay. No significant genetic differentiation was found with microsatellites within or between aggregations. Mean assignment index values were significantly higher for females than males in Jervis Bay, but not in Sydney. Both females and males migrate inshore during the Austral winter for breeding, but it appears females may exhibit higher levels of reproductive philopatry than males. This is the first study to document reproductive philopatry in an oviparous shark, highlighting the importance of conserving and appropriately managing breeding sites for H. portusjacksoni and potentially other oviparous shark species.