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The seven species of rock lobster in the genus Jasus have a fragmented circumpolar distribution, inhabiting continental or island waters of the Southern Ocean. Gene flow between nominal species is possible as the planktonic larval stages of Jasus are widely dispersed in major oceanic gyres. Restriction endonuclease analysis of mitochondrial DNA (mtDNA) from five species (J. verreauxi, J. novaehollandiae, J. edwardsii, J. lalandii and J. tristani) was used to assess taxa previously defined only by morphological criteria. Intraspecific mtDNA nucleotide sequence diversity was generally high (0˙33–0˙99%). An absence of episodic population bottlenecks and extinctions, attributable to a teleplanic (far wandering) and prolonged pelagic stage, may be a significant factor contributing to this variation. New Zealand (J. edwardsii) and Australian (J. novaehollandiae) populations appear to be conspecific and should be referred to as J. edwardsii; however, a significant difference in the magnitude of mean sequence diversities between these populations may indicate restrictions to gene flow across the Tasman Sea. The genome of J. verreauxi is highly distinct from the genomes of the other species (nucleotide sequence diversity: 14˙92–16˙67%), supporting the existence of ‘verreauxi’ and ‘lalandii’ groups within Jasus. High sequence diversities separating J. edwardsii, J. lalandii and J. tristani (4˙41–7˙36%) indicates longterm reproductive isolation. Hypotheses for the evolution of ‘lalandii’ group Jasus, which suggest a relatively recent divergence of J. lalandii and J. tristani, are not supported by phylogenetic reconstruction. Instead, it gives systematic validity to the grouping of J. lalandii with J. edwardsii as proposed by the existing taxonomy.

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