Hierarchical competition in pond-breeding anuran larvae in a Mediterranean area

Abstract

AbstractThe anuran larval guild is frequently characterised by the co-occurrence, with high niche overlap, of distinct species in the same pond at variables densities during development. Anuran larvae have therefore been widely studied as a model system for competition. Body size and activity level are considered the most important factors that influence the outcome of competition between tadpoles. As species from temporary ponds normally show higher activity levels in order to achieve rapid growth and thus reduce the risk of desiccation, these species are often considered superior competitors. We designed several laboratory experiments to examine the intra- and interspecific effects on growth rate, mass at metamorphosis and survival to metamorphosis of six species in a Mediterranean area. Body size and activity level were used as explanatory covariables to determine competitive ability among species. An asymmetric and hierarchical relationship was found among the six species. Larger tadpole species were more successful in competitive interactions than smaller ones, but no relationship was found between activity level and competition effects. Species typically found in temporary ponds (Pelodytes punctatus and Bufo calamita) were considered poor competitors in contrast with other communities studied. Species with low competitive ability can persist by using refuges in which competition is reduced (e.g. ephemeral ponds).