Colonization of temperate grassland by ants

Abstract

Land-use change creates mosaics of habitats of different successional stages in landscapes. Knowledge about successional changes in species richness and community composition is essential for understanding biodiversity change in landscapes. Here we report about the community dynamics associated with the colonization of temperate grassland by ants. The study was carried out in low-intensity farming systems in Central Hesse, Germany, where the area covered by managed grasslands has continuously increased over the last decades. The simultaneous availability of grassland sites of different age allowed us to apply the ‘space-for-time substitution’ approach as a surrogate for a long-term study on ant succession. Our study on the community dynamics associated with the colonization of temperate grassland by ants did not reveal any drastic changes in species richness or composition in time. We nevertheless found clear differences between different phases of ant succession. Our data indicate a community driven by factors such as resistance to anthropogenic disturbance and opportunistic colonization during the initial period of ant succession. Ant composition was highly variable during early successional phases due to the strong site-specific differences in the distribution and abundance of pioneering species. Later successional phases, in contrast, showed much less variation in species composition, providing strong evidence for a rather predictable ant community in mature grasslands in this region. We found a change from ground nesting species that predominantly forage above-ground to the increasing abundance of the hypogaeic Lasius flavus foraging mainly below-ground. This change marks an alteration of the functional structure of the ant community.