Predator associated morphology in Galaxias platei in Patagonian lakes

Abstract

Among 158 Galaxias platei individuals, collected from nine deep Andean lakes and from one shallow lake on the Patagonian steppe, morphological characters associated with caudal fin length were negatively correlated with predation intensity as measured by the incidence of piscivory. Fish from lakes with high rates of piscivory had relatively short caudal fins and those from lakes with low piscivory had long caudal fins. It is hypothesized that in this species caudal fin length affects swimming ability and thus, ability to escape from predators. The population of G. platei from Lake Espejo with an intermediate level of piscivory contained individuals with both long and short caudal fins. Morphological variation within this lake was related to the exploitation of food resources and habitat; individuals with shorter tails ate more amphipods and inhabited shallower habitats. The results indicated that while the among‐lakes morphological variation in G. platei was influenced largely by differences in predation intensity, within‐lake morphological variation, where predation was intermediate, appeared to be affected by both predation and differences in the exploitation of food resources.