Palaeoceanography and Speciation in the Spiny Lobster Genus Jasus

The wide geographic range of spiny lobsters of the genus Jasus around the southern hemisphere is accounted for by long-distance dispersal of teleplanic phyllosoma larvae. Larvae from a South Pacific ancestral Jasus species presumably entered the South Atlantic when circumantarctic circulation developed between 29 and 20 million years ago. Subsequent colonization of islands, seamounts and continental regions in the Atlantic and Indian Oceans is thought to have taken place during late Tertiary and Quaternary glacial periods. Most present-day populations maintain separate species identity, with little evidence of genetic interchange, despite the fact that larvae tend to share the same or similar dispersal and return routes in the large-scale eddies and sub-gyres within the overall anticlockwise circulation systems of each of the three ocean basins. Species integrity appears to be maintained by behavioral barriers to larval recruitment, caused by larval responses to chemical and physical cues specific to “home” environments, which induce the final stage phyllosoma larvae to metamorphose into the competent settling stage, the puerulus larva. It is suggested that changes in palaeocirculation systems may have been associated with changes in sea level and emergence and subsidence of seabed ridges, rises and seamount chains, and that such changes in current systems may have accelerated the processes of speciation and extinction in some spiny lobster species.