Relationships among habitat, ecomorphology and diets of cichlids in the Bladen River, Belize

Abstract

The Neotropical Cichlidae is among the most species-rich and ecologically diverse groups of freshwater fishes. This study investigated interspecific morphological and ecological relationships within an assemblage of six cichlids in the Upper Bladen River, Belize. This portion of the river drains a nearly pristine watershed within a nature reserve, and thus should provide a natural ecological context for interpretation of ecological patterns. Species distributions within morphological, habitat and dietary space yielded patterns consistent with a hypothesis of niche partitioning. Statistical analyses of the species assemblage revealed relationships between two principal morphological gradients from multivariate analysis with several diet and habitat variables, and these patterns were consistent with prior functional morphological interpretations. Given that this local cichlid assemblage contains no congeneric species, it is apparent that morphological divergence resulting in niche segregation reflects selective establishment of species from a more species-rich regional species pool rather than in situ adaptive evolution.