Isolation drives species gains and losses of insect metacommunities over time in a mountaintop forest archipelago

Aim: We evaluated the effects of forest island size, isolation, and area in the landscape driving temporal changes of insect biodiversity in a mountaintop forest archipelago. We tested the following hypotheses: (i) changes in insect species composition is higher and dominated by species gains through time in smaller but less isolated forest islands; (ii) larger amounts of forest in the landscape result in higher gains of more vagile species over time, regardless of their size and isolation; (iii) heterogenization processes will prevail in less vagile groups, while homogenization processes will dominate in highly vagile groups due to differences in dispersal capability.

Location: Espinhaço Range Biosphere Reserve, Brazil.

Taxon: Insects.

Methods: We used ants, dung beetles, bees, wasps, and butterflies as study models to represent a gradient of low-to-high dispersal capability. We evaluated the colonization- and extirpation-resultant components of temporal β-diversity using area- and isolation-related variables as predictors.

Results: We found distinct colonization- and extirpation-resultant homogenization and heterogenization processes acting according to each insect group, likely due to different dispersal capabilities. Ants were dominated by species losses, with widespread and rare species being lost. Butterflies gained species, represented mainly by widespread species, leading to an increased colonization-resultant homogenization. Distance to neighboring forest islands was the underlying predictor affecting the temporal β-diversity of insect groups and on species gains and losses but differed according to the survey period. Effects of the forest amount in the landscape increased the temporal β-diversity of bees and butterflies but decreased that of ants, dung beetles, and wasps.

Main Conclusions: We recommend conserving the forest amount in the landscape and keeping forest connectivity among forest islands since the temporal dynamics of local colonization and extirpation can depend on the organisms' dispersal capability. Fragmentation and habitat loss-related hypotheses will benefit from incorporating colonization-extirpation processes into their predictions.