Extreme life history plasticity and the evolution of invasive characteristics in a native ant

Disturbance resulting from urbanization is a leading cause of biotic homogenization worldwide. Native species are replaced with widespread non-native species and ants are among the world's most notorious invaders. To date, all documented cases of ant invasions involve exotic introduced species that are spread around the world by human-mediated dispersal. I investigated the effect of urbanization on the evolution of invasive characteristics in a native ant species, the odorous house ant, Tapinoma sessile (Say). Colony social structure, life history traits, and the spatial pattern of nest distribution were compared by sampling T. sessile across a gradient of three distinct habitats: natural, semi-natural, and urban. Results demonstrate a remarkable transition in colony social and spatial structure and life history traits between natural and urban environments. In natural habitats, T. sessile colonies are comprised of small, monogyne (single queen), and monodomous (single nest) colonies. In urban areas, T. sessile often exhibit extreme polygyny and polydomy, form large supercolonies, and become a dominant pest. Results also suggest that urban T. sessile colonies may have a negative impact on native ant abundance and diversity. In the natural environment T. sessile coexisted with a wide array of other ant species, while very few ant species were present in the urban environment invaded by T. sessile. Habitat degradation and urbanization can lead to extreme changes in social and spatial colony structure and life history traits in a native ant species and can promote the evolution of invasive characteristics such as polygyny, polydomy, and supercolonial colony structure.