High connectivity and lack of mtDNA differentiation among two previously recognized spiny lobster species in the southern Atlantic and Indian Oceans

Adult spiny lobsters Jasus paulensis and J. tristani inhabit non-emergent seamounts and remote islands in the southern mid-latitude (30-45 degrees S) Indian and Atlantic Oceans. Populations are often thousands of kilometres apart, and metapopulation genetic structure relies on successful exchange of long-lived drifting larvae. Genetic population structure and connectivity were investigated by sequencing the mitochondrial cytochrome oxidase I gene from lobsters collected at two Indian Ocean sites (Seamount 150 and St Paul/Amsterdam Islands) and two Atlantic sites (Vema Seamount and Gough/Inaccessible Islands) between 2006 and 2011. Jasus paulensis and J. tristani individuals share identical haplotypes across the distribution range and Bayesian phylogenetic analyses strongly support the monophyly of all individuals sampled, to the exclusion of all other recognized Jasus species. Analyses of molecular variance revealed no significant population genetic differentiation between sites, and Fu's F-s and a mismatch distribution suggested demographic expansion, which was estimated to have occurred between 14,000 and 118,000 years ago. The results show an apparent lack of barriers to dispersal and gene flow over thousands of kilometres of the southern Indian and Atlantic Oceans, and suggest that J. paulensis and J. tristani should be synonymized as J. paulensis (Heller, 1862).