Passive and active dispersers respond similarly to environmental and spatial processes: an example from metacommunity dynamics of tree hole invertebrates

Abstract

The role of environmental and spatial processes and the strategies of organism dispersal in structuring local communities are still controversial. We used data from 41 water-filled tree holes in the Atlantic Forest biome (Brazil) to evaluate the relative role of local environmental and spatial variables as drivers of metacommunity structure. Our main focus was to investigate beta diversity patterns produced by groups of organisms characterized by active and passive dispersal. We expected that habitat conditions would explain the largest portion of variation in metacommunity structure and that, considering strategies of organism dispersal, an increased importance of spatial variables would be detected for organisms with passive dispersal when compared to those with active dispersal. No significant effect of either environment or space was observed on the overall invertebrate community structure, active dispersal group, or passive dispersal group. The monopolization of the habitat by a pioneer species may partly explain the lack of significant relationships, as some of the water-filled tree holes were characterized by the occurrence of a single taxon - a passive disperser. The passive dispersal group may be the main settler of these habitats, given that their habitat requirements are probably low, because their settlement location is determined by their host. Even discarding possible sources of uncertainty in our data, the understanding of the processes and mechanisms that are represented by the high residual variation still remains unclear in these tree hole metacommunities.