DNA Taxonomy Confirms the Identity of the Widely-Disjunct Mediterranean and Atlantic Populations of the Tufted Ghost Crab Ocypode cursor (Crustacea: Decapoda: Ocypodidae)

The distribution area of the tufted ghost crab Ocypode cursor includes two widely separatesub-areas, i.e. the tropical and subtropical Atlantic coasts of Africa and Macaronesia, and thecentral-eastern Mediterranean basin. The current disjunct distribution of the species is possiblythe remnant of a previous wider and continuous distribution area that was fragmented during thePleistocene, with the disappearance of the species from the temperate Atlantic Ocean and thewestern Mediterranean basin, and its survival in the warmer areas of the eastern Atlantic and theMediterranean Sea. Such disjunction is thus compatible with an ancient isolation between theMediterranean and Atlantic populations of the species, which could in fact constitute two wellcharacterizedindependent evolutionary lineages, or even two cryptic species. Unexpectedly, thesequencing of a fragment of the mtDNA COI gene from Mediterranean and Atlantic Ocypode cursorallopatric populations showed the cohesion of the species throughout its distribution range, andthe nesting of Mediterranean populations within the single Atlantic population studied. This patternis hereby tentatively ascribed to an incomplete lineage sorting due to the large populationsizes of both the Atlantic and Mediterranean subpopulations of the species. The current westwardexpansion of the species in the Mediterranean Sea originating from the Levantine basin, due toongoing regional sea warming, follows a typical phalanx dispersal mode.