MICROSATELLITES REVEAL HIGH POPULATION VISCOSITY AND LIMITED DISPERSAL IN THE ANT FORMICA-PARALUGUBRIS

We used microsatellites to study the fine-scale genetic structure of a highly polygynous and largely uni-colonial population of the ant Form ica paralugubris. Genetic data indicate that long-distance gene flow b etween established nests is limited and new queens are primarily recru ited from within their natal nest. Most matings occur between nestmate s and are random at this level. In the center of the study area, buddi ng and permanent connections between nests result in strong population viscosity, with close nests being more similar generically than dista nt nests. In contrast, nests located outside of this supercolony show no isolation by distance, suggesting that they have been initiated by queens that participated in mating flights rather than by budding from nearby nests in our sample population. Recruitment of nestmates as ne w reproductive individuals and population viscosity in the supercolony increase genetic differentiation between nests. This in turn inflates relatedness estimates among worker nestmates (r = 0.17) above what is due to close pedigree links. Local spatial genetic differentiation ma y favor the maintenance of altruism when workers raise queens that wil l disperse on foot and compete with less related queens from neighbori ng nests or disperse on the wing and compete with unrelated queens.