Ongoing Phenotypic and Genotypic Diversification in Adaptively Radiated Freshwater Crabs from Jamaica

Abstract The Caribbean island of Jamaica is home to a lineage of crabs (Crustacea: Decapoda: Brachyura: Sesarmidae) which have colonized the most unusual terres-trial habitats. Today, they can be found nesting in bromeliad leaf axils or empty snail shells, scurrying on the forest floor or among dry rock rubble, climbing on walls of deep cave systems, or digging burrows in the banks of mountain streams. In order to facilitate survival of their offspring in these remarkable and new habitats, complex behavioral adaptations have evolved, including feeding and protecting the offspring, and transport of empty snail shells into the nursery to buffer the pH and provide the necessary calcium carbonate [summarized in Diesel (Proc Roy Soc Lond B 264:1403–1406, 1997), Diesel and Schubart (Evolutionary ecology of social and sexual systems: crustaceans as model organisms. Oxford University Press, New York, pp 365–386, 2007)]. No other American sesarmid crab species shows this degree of terrestriality and elaborate brood care behavior. Instead, the most related species typically are inhabitants of marshes and mangroves and reproduce by releasing their larvae into the ocean, without any additional paterna