Ecomorphological relationships of fish assemblages in a trans-Andean drainage, Upper Magdalena River Basin, Colombia

ABSTRACT Ecomorphological patterns of the fish community were evaluated in the trans-Andean Alvarado River drainage, Colombia. A total of 29 species using 25 ecomorphological indices were analyzed to test how well the ecomorphological patterns are related to the fish assemblage. Although a significant correlation was found (Mantel test) between morphological attributes and trophic guilds, habitat use and distribution across the altitudinal gradient, only the last two were significantly independent of the phylogenetic relationships (partial Mantel test). Regarding the ecomorphological space, two main trends were defined. First, benthic periphytivores and invertivores were characterized by having dorsal or dorsolateral eyes, labial appendages, depressed bodies and well-developed pectoral, ventral and caudal fins, which provide them the ability to stabilize over the substrate and make rapid movements. Second, nektonic detritivore-invertivores and insectivores were found to have laterally compressed bodies, lateral eyes and larger eyes and anal fins. These species use vision during predation, are good continuous swimmers and possess higher maneuverability and stability. These results show that the fish assemblages in the Alvarado River drainage are structured ecomorphologically mainly by habitat and the altitudinal gradient. Therefore, this is evidence of the importance of habitat structure to maintain the functionality of the ecosystem.