Shell resource partitioning among three intertidal hermit crab species

Abstract

Resource partitioning is an important mechanism that facilitates the coexistence of diverse organisms. Hermit crabs depend on the empty shells of gastropods for protection against predation; however, a short supply of this resource results in intense fighting over shells and competition among hermit crab species. To examine whether hermit crab species mitigate shell competition through resource partitioning, we studied the distribution pattern, shell utilization pattern, and frequency of ovigerous Pagurus filholi, Pagurus nigrivittatus, and Clibanarius virescens females, all of which are abundant hermit crab species in the intertidal shore in the Shikoku region of Japan. We found that P. filholi and C. virescens essentially live in sympatry, while P. nigrivittatus prefers a lower intertidal habitat compared to that by the other two species. Additionally, we found a significant difference among the patterns of shell species utilization between P. filholi and C. virescens. Further, while the proportion of ovigerous females reached approximately 30% in C. virescens and P. nigrivittatus, only a few P. filholi females reproduced in our study, suggesting that they breed in distinct temporal windows. Our results demonstrate that these three common hermit crabs spatially and temporally partition their resources, which potentially mitigates interspecific competition.