Suburban ant community structure with emphasis on Tapinoma sessile and T. sessile colony movement in the laboratory

Urbanization causes profound changes in the organization of arthropod communities. Ants, in particular, are good study subjects for community ecology and modification of habitat by humans has been shown to impact their community richness and composition. Of particular interest is how human-modified habitat affects the populations of pest ants such as the odorous house ant, Tapinoma sessile (Say). To better understand the relationship between urban habitat and ant community structure, ant communities in urban and suburban yards in the Knoxville, TN area were sampled via pitfall trapping and baiting, and several habitat characteristics were measured. Forty-six ant species were collected from twenty-five yards. Close proximity to human structures had the strongest relationship with both species richness and T. sessile abundance, with the former decreasing near structures while the latter increased.Of habitat characteristics quantified, percentage canopy cover was the most strongly related to ant species richness. These two variables had a polynomial relationship with highest richness at intermediate levels of canopy cover. Additionally, species richness had a significant, but negative, relationship with leaf litter presence. Leaf litter and the presence of logs, boards, or landscaping timbers positively related to T. sessile abundance. As T. sessile colonies are known to move frequently, possible triggers of colony movement were examined in the laboratory including: shade, moisture, and proximity of food. Tapinoma sessile colonies initially moved to shaded nest tubes regardless of moisture content, but eventually moved brood and workers to moist nest tubes over a several week period. Colonies moved workers and brood to near-food nest tubes regardless of foraging distance to food.Queens moved to near-food nest tubes over 1 m distances, but not 6 m distances, during the 49 day study. Increases in moisture or food near houses may account for the dramatic rises in T. sessile abundance near these structures.