Effects of Interspecific Competition on Fitness of the Hermit Crab Clibanarius Tricolor

Abstract

Clibanarius tricolor overlaps strongly in shell utilization with the other common species of intertidal hermit crabs found in the Florida Keys. Laboratory observations indicated C. tricolor can dominate Clibanarius antillensis in shell fights, while Calcinus tibicen dominates C. tricolor. In micro—areas of sympatry with C. antillensis, C. tricolor's shell fit is better and egg production parameters not affected when compared to adjacent areas where only C. tricolor occurs. Sympatry with Calcinus tibicien in a poorer shell fit, a smaller shell size for a given size crab, a smaller mean size of crab, and a disruption of the relationship between clutch size and crab size:shell weight ratio. A strong effect of shell species on the probability of ♀ ♀ being ovigerous was noted. It is suggested that the ecological separation which characterizes these species over most of their ranges was an evolutionary response, in part, to the effects of interspecific shell competition.