Small Changes in Vegetation Structure Create Great Changes in Amphibian Ensembles in the Colombian Pacific Rainforest

Abstract

This study determines the composition of amphibian ensembles along a vegetation gradient in the coastal Pacific rainforests in Colombia. Eight environmental and structural variables were measured to characterize the species' habitats and to determine which was most important in structuring amphibian patterns. After a total of 432 man-hours sampling effort, 513 individuals from 32 amphibian species were found. Although the species richness was similar among the vegetation cover types, the composition of the ensembles and total amphibian abundance were different in each case. In addition, a strong relationship was found between changes in the vegetation structure and the amphibian pattern, with the canopy cover being the key variable in the composition of the ensembles for each cover type. Habitats with over 76% canopy cover, combined with a high density of individual woody plants (> 176 individuals per 500 m2) and a high depth of leaf litter (> 16 cm), provide the necessary habitat conditions for typical rainforest composition of amphibian species. However, for amphibian ensembles to have a mature forest composition, the habitat must have a canopy cover over 89%, a density of woody plants exceeding 231 individuals per 500 m2, and a leaf litter depth above 23 cm. Therefore, future studies of amphibian succession and restoration in tropical forests must determine the changes in vegetation structure, rather than the possible direct effect of microclimatic variables.