Ontogenetic changes in habitat use and diet of the sea-starHeliaster helianthuson the coast of central Chile

Abstract

Ontogenetic shifts in habitat use and diet are ubiquitous in nature and usually have profound consequences for the ecology and evolution of the species. In the case of species with strong interactions within their communities, such as keystone predators, understanding this kind of size-related change is critical to understand variation and connectivity among spatially distinct habitats of coastal communities. Yet the ecology of early life stages of marine benthic invertebrates, particularly asteroids, is poorly understood. Here we describe the results of surveys to characterize the habitat and quantify the abundance and diet of recruits of the sun starHeliaster helianthus, a keystone predator at rocky intertidal sites in central Chile. Our results support the existence of size-related, ontogenetic changes in habitat use and diet of this species. Recruits occupy boulders and crevices in the high or mid-high intertidal zones of wave-protected habitats and as they grow they move down towards lower tidal levels. Adults are characteristically found in the low intertidal zone of wave exposed and semi-exposed habitats. These changes in habitat use are accompanied by changes in diet composition and particularly by a broadening of the prey species incorporated in the diet. Since early stages ofHeliasterappear to be most sensitive to predation and abiotic stress and since adults are such important predators in wave exposed rocky shores, knowledge of the basic ecology of early stages of this species is critical to fully understand the dynamics of intertidal communities.