Geospatial and environmental drivers of genetic divergence in the Indo-West Pacific spiny lobster Panulirus ornatus

The tropical ornate spiny lobster, Panulirus ornatus, is distributed widely across the Indo-West Pacific and is a highly valued seafood species. The fine-scale genetic structure of this species was examined using 13 microsatellite loci from 298 lobsters collected from 17 locations from Tanzania in the west to New Caledonia in the east and compared with mitochondrial DNA (mtDNA) and genomic (SNP) from previous studies. Significant overall genetic differentiation was observed in the microsatellite data (F'(ST) = 0.051, P < 0.001), but these geographic patterns differed somewhat from those seen previously in mtDNA and SNP data. For both nuclear DNA (nDNA) and mtDNA there was significant genetic divergence and reduced diversity in lobsters from Western Australia and New Caledonia, likely due to genetic bottlenecks. However, the previously identified strong divergence of lobsters from the West Indian Ocean was only minimally supported in the microsatellite data, suggesting some recent gene flow across this region had eroded past divergence in this lineage. Geographic, environmental and ocean current variables were used to detect those factors associated with genetic divergence at both mtDNA and nDNA loci. Population divergences were only partially explained by geography and were not strongly related to ocean currents. Instead, there were significant associations with ocean vorticity, convergence and sea surface temperature. These implicate strong eddy systems, characterised by high levels of convergence and/or vorticity, in constraining larval dispersal. Overall, these findings help to identify the processes driving the genetic structure of P. ornatus populations and the results have considerable implications for the management of wild fisheries for this species.