Ant species assembly in constructed grasslands is structured at patch and landscape levels

Agri-environmental incentive programmes encourage conversion of marginal agricultural land to grasslands to reduce soil erosion and support biodiversity of native flora and fauna. Most grassland animals colonise these constructed habitats as propagules from the surrounding landscape. Ants are slow to colonise and rely on resources within the patch, making them valuable as indicators of disturbance and recovery. We studied how ant species diversity and composition are structured by patch and landscape variation of grasslands in Ohio, USA. Ant communities were collected from 23 constructed grasslands differing in area, age, vegetation, soils, management and surrounding land cover. We analysed trap frequency for 14 species that varied in habitat specialisation to identify species responses to patch- and landscape-level predictors. Grassland age and soil texture determined ant species richness and community composition. Trap frequency analysis showed contrasting species responses to patch and landscape characteristics: habitat specialists were more abundant in older, larger patches with more surrounding grassland, while disturbance-tolerant species were more frequent in younger patches surrounded by intensive agriculture. Habitat generalists and open habitat species included a variety of patch- and landscape-level factors in best models. Ant community assembly in constructed grasslands is shaped by time and physical characteristics at the patch-level, but the surrounding landscape acts as a filter for the colonising community. Our findings support the use of ants as ecosystem recovery indicators following disturbance in agricultural landscapes, but show that shifts in species composition are better indicators of grassland habitat variation than ant richness.