Long current to nowhere? — Genetic connectivity of Jasus tristani populations n the southern Atlantic Ocean

Abstract

The commercially exploited spiny lobster Jasus tristani has a disjunct distribution in the southern Atlantic Ocean, with populations occurring at the Tristan da Cunha Archipelago, Gough Island and on Vema Seamount. A distance of 2 000km separates Vema and the Tristan Archipelago. In order to determine genetic connectivity of lobster between these locations, a region of the cytochrome oxidase II (COII) gene was sequenced for 193 individuals of J. tristani from five sampling sites (Tristan da Cunha, Nightingale, Inaccessible, Gough islands and Vema Seamount). Our results show that J. tristani in the southern Atlantic share a most recent common ancestry that dates back at least one million years. Analyses of molecular variance and pairwise Φ_st analyses reveal shallow but significant genetic partitioning between Vema Seamount and all other locations. No population differentiation was detected among any of the remaining sampling sites. Coalescent analyses show limited gene flow between Vema and the archipelago (including Gough Island), possibly mediated by larval dispersal in the South Atlantic gyre system. Population divergence between Vema and the other populations, using MDIV, was estimated to be approx. 270 000 years ago. Mismatch distributions, a haplotype network, and Fu's F_s test, all suggest that the J. tristani population underwent population expansion between 12 000 and 99 000 years ago.

Keywords: Jasus tristani, larval dispersal, MDIV, mitochondrial DNA, population genetic structure, seamount, southern Atlantic Ocean

African Journal of Marine Science 2007, 29(3): 491–497