Something is lost and something is gained: loss and replacement of species and functional groups in ant communities at fragmented forests

Context Small fragments of natural habitats with an increased proportion of edges are common landscape traits following agricultural expansion. Consequences of habitat fragmentation are widely documented. However, functional and mechanistic approaches are still needed in order to understand these changes. Objectives We studied habitat loss and edge effects on ant communities, addressing changes in species and functional group diversity, and the relative importance of β-diversity components. Methods In an endangered Neotropical forest, we sampled ants in edge and interior habitats using pitfall traps, during three summers (28 sites). We calculated taxonomic, phylogenetic and functional diversity and partitioned taxonomic and functional β-diversity into replacement and loss/gain components. Results We found more species and functional groups at edge than interior habitats, and four species were edge indicators. Habitat loss negatively affected total abundance and that of particular functional groups (fungus-growers and cryptic species) but had a positive effect on taxonomic, phylogenetic and functional diversity as well as abundance of opportunists and predators. Species and functional group replacement drove β-diversity, being linked to habitat loss. However, interactions between habitat loss and edges explained the loss/gain of taxonomic and functional composition. Conclusions Fragmentation led to enriched ant communities at edges, possibly resulting from a higher influx of matrix species as edges become pervasive. This highlights the need to assess the spillover between habitats to understand its influence. Moreover, species replacement and the decrease of functional groups due to habitat loss could have an impact on ecosystem processes in which ants play an important role.