Phylogeography of the scalloped spiny-lobster Panulirus homarus rubellus in the southwest Indian Ocean

Abstract

The Mozambique Channel between south-east Africa and Madagascar potentially forms a barrier to larval dispersal and thus gene flow across the channel, even in species with long larval lifespans such as spiny lobsters. The DNA of 181 specimens of Panulirus homarus rubellusBerry, 1974, collected from six sites along the African coast and a site in Madagascar, was sequenced (591 base pairs) to investigate gene flow along the coast and across the channel. Bayesian methods were implemented to infer genetic structure and relatedness. A total of 112 haplotypes were recovered, of which |$78\%$| were unique. Samples from Africa and Madagascar did not share any haplotypes and differed by 78 mutations and |$3\%$| DNA divergence. These distinct lineages suggest an absence of contemporary gene flow across the Mozambique Channel. Shallow genetic structure along approximately |$1000\;{\rm{km}}$| of African coastline comprised combinations of seven distinct lineages but did not correspond to known biogeographic provinces. The African lineage appeared to be ancestral, and the source population for the Madagascan clade. Genetic isolation in refuges during glacial periods, followed by subsequent range expansions and secondary contact, may account for the high diversity in the African lineages.