Forest fragmentation changes macroinvertebrate community composition in neotropical treeholes

Abstract

Habitat loss and fragmentation are the main drivers of biodiversity loss in terrestrial ecosystems, particularly in the tropics. Fragmented habitats can interfere with organism dispersion, population persistence and ecosystem functions but empirical studies report wide variation in the sensitivity of organisms and functions to fragmentation and the mechanisms operating behind observed responses remain poorly understood. In this study we examined the effects of forest fragmentation on the colonization of artificial treeholes in northwestern Costa Rica by measuring the responses at the community level. We explored four potential mechanisms driving differences in macroinvertebrate communities between continuous and fragmented forests: dispersal limitation, microclimate changes and bottom up or top down effects. Macroinvertebrate community composition differed significantly between continuous forests and forest remnants but not in the predicted direction. Our results suggest that treeholes in fragmented forest contain higher abundance of detritivores and experience changes in predator species identity consistent with increased nutrient input and a potential relaxation of predation pressure in small forest remnants. An overall resilience of treehole communities to forest fragmentation is interpreted with care as time-delayed responses to fragmentation continue to be a possibility. These findings advance our understanding of the response of biological communities to forest fragmentation and emphasize the value of preserving even small forest remnants for biodiversity conservation.