Competition conditional on recruitment and temporary escape from predators on a tropical rocky shore

Abstract

On a rocky headland on the Pacific Coast of Costa Rica we document a period of heavy recruitment of the barnacle, Chthamalus fissus Darwin, in an area infrequently visited by its major predator, the muricid gastropod, Acanthina brevidentata (Wood). For much of 1984, Chthamalus fissus occupied most available free space in the area, appearing to surround and imprison pulmonate limpets, Siphonaria gigas (Sowerby), on their home scars. Limpets lost weight when imprisoned, a situation which persisted until barnacles were removed by Acanthina brevidentata predation. Limpets had little effect on barnacles. Heavy barnacle recruitment in predator-free areas occupied by the limpet is unpredictable in space and time. As a result the negative effect of barnacles on limpets probably has little evolutionary consequence for the limpet.