Multivariate dispersions of composition vs abundance as drivers of beta diversity in parasite assemblages of Serranus auriga (Serranidae) along host ontogeny.

BRAICOVICH, P.E.; TIMI, J.T.

Viña del Mar

Simposio; VIII International Symposium on Fish Parasites; 2011

Universidad de Antofagasta, Chile

Parasite communities are dynamic systems driven by many interacting factors, among them host ontogeny produces variations in composition and abundance of parasites within assemblages, depending on changes in age, size and trophic level. It has been shown that juvenile fish or those with low trophic level harbour more variable assemblages than their counterparts. Here we analyze the ontogenetic changes in parasite assemblages of Serranus auriga, a species with low trophic level, which reaches small sizes at adult stage and feed on similar prey items along its life span. In order to assess the relative role of composition and abundance as drivers of changes in assemblage’s structure, multivariate dispersions of infracommunities as measures of b-diversity were calculated using a set of dissimilarity measures with different degrees of emphasis on composition vs. relative abundance information. The average distance from infracommunities to their size class centroid in the multivariate space varied significantly along an ontogenetic gradient for those distance measurements emphasizing abundance, but not for those emphasizing composition. Stochasticity in events of encounter with infective stages, occurring at low densities in previous invertebrate hosts, which seem to be maintained along fish life-span, explains this pattern. On the other had, and as fish grow, assemblage´s composition becomes variable in terms of abundance, but increasing also aggregation of parasite populations, which render higher inter-host differences within samples of larger fish.