Resource Partitioning by Predatory Gastropods of the Genus Conus on Subtidal Indo-Pacific Coral Reefs: The Significance of Prey Size

Abstract

On subtidal reefs, most Conus species that feed on errant polychaetous annelids spe- cialize on various members of the family Eunicidae, whereas on intertidal benches, members of the family Nereidae dominate the diet. There are at least 2 groups of Conus species (termed complexes) that share major prey species on reefs in Micronesia and the Indian Ocean. Members of these respective groups feed primarily on the eunicids Palola siciliensis and Eunice afra. There are also 2 such groups on reefs in Hawaii, one feeding on Palola siciliensis and the other on Eunice australis, plus a Lysidice collaris specialist and a Eunice afra specialist. Mean prey sizes of Conus species within such feeding complexes tend to differ. Mean prey sizes, mean sizes of particular prey species, and mean body sizes of Conus species within feeding complexes differ more often on subtidal reefs than on intertidal benches. Furthermore, mean prey-size overlap between Conus populations on subtidal reefs is less than (but on intertidal benches not different from) a random expectation derived by a new technique described in this paper. It is suggested that divergence in food and body size of Conus, possibly in response to competition, has occurred on subtidal reefs where food may limit its abundance, but not on intertidal benches where food is probably superabundant.