The Question of Coexistence in Hermit Crabs: Population Ecology of a Tropical Intertidal Assemblage

Abstract

The hermit crab assemblage of Calcinus laevimanus, Ca. latens, and Clibanarius humilis was studied on the intertidal rocky shores of the Maldivian atolls. The species were segregated across the intertidal area, Ca. laevimanus and Cl. humilis occurring in the midlittoral zone and supralittoral fringe, and Ca. latens in the infralittoral fringe and shallow subtidal. Habitat partitioning may be responsible for the coexistence of the two dimensionally closest species, Ca. laevimanus and Ca. latens. Resource partitioning probably plays the greater role in allowing Cl. humilis to share the same macro- and microhabitats with the larger and possibly dominant Ca. laevimanus, since the two species occupy gastropod shells with opposite architecture. However, patterns of growth and morphology, reproductive traits, as well as the different ecological role of shell types, can negate the impact of resource overlap between these two coexisting species, since these differences may possibly have evolved under pressures other than interspecific competition for resources.