Genome-wide SNPs in the spiny lobster Panulirus homarus reveal a hybrid origin for its subspecies.

BACKGROUND: Evolutionary divergence and speciation often occur at a slower rate in the marine realm due to the higher potential for long-distance reproductive interaction through larval dispersal. One common evolutionary pattern in the Indo-Pacific, is divergence of populations and species at the peripheries of widely-distributed organisms. However, the evolutionary and demographic histories of such divergence are yet to be well understood. Here we address these issues by coupling genome-wide SNP data with mitochondrial DNA sequences to test the patterns of genetic divergence and possible secondary contact among geographically distant populations of the highly valuable spiny lobster Panulirus homarus species complex, distributed widely through the Indo-Pacific, from South Africa to the Marquesas Islands. RESULT: After stringent filtering, 2020 SNPs were used for population genetic and demographic analyses, revealing strong regional structure (FST = 0.148, P < 0001), superficially in accordance with previous analyses. However, detailed demographic analyses supported a much more complex evolutionary history of these populations, including a hybrid origin of a North-West Indian Ocean (NWIO) population, which has previously been discriminated morphologically, but not genetically. The best-supported demographic models suggested that the current genetic relationships among populations were due to a complex series of past divergences followed by asymmetric migration in more recent times. CONCLUSION: Overall, this study suggests that alternating periods of marine divergence and gene flow have driven the current genetic patterns observed in this lobster and may help explain the observed wider patterns of marine species diversity in the Indo-Pacific.

Genetic and particle modelling approaches to assessing population connectivity in a deep sea lobster.

The emergence of high resolution population genetic techniques, such as genotyping-by-sequencing (GBS), in combination with recent advances in particle modelling of larval dispersal in marine organisms, can deliver powerful new insights to support fisheries conservation and management. In this study, we used this combination to investigate the population connectivity of a commercial deep sea lobster species, the New Zealand scampi, Metanephrops challengeri, which ranges across a vast area of seafloor around New Zealand. This species has limited dispersal capabilities, including larvae with weak swimming abilities and short pelagic duration, while the reptant juvenile/adult stages of the lifecycle are obligate burrow dwellers with limited home ranges. Ninety-one individuals, collected from five scampi fishery management areas around New Zealand, were genotyped using GBS. Using 983 haplotypic genomic loci, three genetically distinct groups were identified: eastern, southern and western. These groups showed significant genetic differentiation with clear source-sink dynamics. The direction of gene flow inferred from the genomic data largely reflected the hydrodynamic particle modelling of ocean current flow around New Zealand. The modelled dispersal during pelagic larval phase highlights the strong connectivity among eastern sampling locations and explains the low genetic differentiation detected among these sampled areas. Our results highlight the value of using a transdisciplinary approach in the inference of connectivity among populations for informing conservation and fishery management.