Local and regional drivers of ant communities in forest-grassland ecotones in South Brazil: A taxonomic and phylogenetic approach

Understanding biological community distribution patterns and their drivers across different scales is one of the major goals of community ecologyin a rapidly changing world. Considering natural forest-grassland ecotonesdistributed over the south Brazilian region we investigated how antcommunities are assembled locally, i.e. considering different habitats, and regionally, i.e. considering different physiographic regions. We used taxonomic and phylogenetic approaches to investigate diversity patterns and search for environmental/spatial drivers at each scale. We sampled antsusing honey and tuna baits in forest and grassland habitats, in ecotonesdistributed at nine sites in Rio Grande do Sul state, Brazil. Overall, we found 85 antspecies belonging to 23 genera and six subfamilies. At the local scale, we found forests and grasslands as equivalent in antspecies and evolutionary history diversities, but considerably different in terms of species composition. In forests, the soil surface air temperature predicts foraging antdiversity. In grasslands, while the height of herbaceous vegetation reduces antdiversity, treelet density from forest expansion processes clearly increases it. At a regional scale, we did not find models that sufficiently explained anttaxonomic and phylogenetic diversitybased on regional environmental variables. The variance in species composition, but not in evolutionary histories, across physiographic regions is driven by space and historical processes. Our findings unveil important aspects of ant community ecologyin natural transition systems, indicating environmental filtering as an important process structuring the communities at the local scale, but mostly spatial processes acting at the regional scale.