Comparison of feeding guild structure and ecomorphology of intertidal fish assemblages from central California and central Chile

Abstract

The hypothesis of ecological and morphological convergence of the taxonomically distinct intertidal fish assemblages from central California, USA, and central Chile was tested by comparing the feeding guild structures and the morphologies associated with food capture and processing of guild members from each region. We determined the diets of the most abundant intertidal fishes from 3 central California sites by examining gut contents. A matrix of dietary overlap among species within the Californian and Chilean assemblages (diets of Chilean fishes determined in another study) was constructed, and statistically significant guilds were determined using a bootstrapping procedure. Ten morphological features were examined for species in each region, and the relationship between diet and consumer morphology was evaluated. Three feeding guilds, omnivore, microcarnivore, and carnivore, were common to both regions, but a fourth guild, polychaete feeders, was unique to California. Feeding guild structure was not associated with phylogenetic relatedness within either assemblage. An assemblage-wide relationship between diet and morphology was found in each assemblage, but only a few associations between diet and morphology were common to both regions. In both California and Chile, omnivores tended to have longer digestive tracts and closer-set gill rakers, microcarnivores tended to have larger relative mouth heights, and all carnivorous fishes tended to have shorter guts and more widely spaced gill rakers. Overall, interregional morphological patterns were associated with phylogenetic relatedness, rather than with dietary similarities.