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

The anuran larval guild is characterised by the co-occurrence of distinct species in the same pond at high densities during development with a high niche overlap. For these reasons anuran larvae have been studied widely 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 escape from the risk of death due to desiccation of the habitat, these species are considered superior competitors. We will test whether body size or activity level determines competition ability among six species from a Mediterranean anuran community. With this objective we designed several laboratory experiments to examine the intraand interspecific effects on growth rate, mass at metamorphosis and survival to metamorphosis of the six species. An asymmetric and hierarchical relationship was found among the six species. Larger tadpole species were more successful in competitive interactions than the smaller ones. However, no relationship between activity level and competition effects was found. Species typically found in temporary ponds (Pelodytes punctatus and Bufo calamita) were considered poor competitors in comparison with others communities studied. Species with low competitive ability can persist by using refuges in which competition is reduced (e.g. drying ponds).