The relative importance of urbanization and Tapinoma sessile presence in ant biodiversity loss and the abiotic and biotic barriers against odorous house ant invasions
Abstract
Through modifying ecosystem performance and displacing native organisms, invasive species have become a primary threat to global biodiversity. Odorous house ant, Tapinoma sessile (Say), is a “generalist” and “opportunist” species native to North America that expresses invasive ant behaviors such as budding, polydomy, extreme polygyny and atypical levels of aggression. Although T. sessile has only been reported as an invasive species in Hawaii, its potential range of distribution throughout tropical and temperate environments makes odorous house ant a serious threat. This research sought to detail T. sessile’s influence within local ant communities and investigate what abiotic and biotic conditions would facilitate spread of odorous house ant. To better predict possible consequences of T. sessile introduction to foreign ant communities, I surveyed ant community dynamics within natural, semi-natural, and urban habitats in the odorous house ant’s native range. I investigated how T. sessile presence and habitat differences impacted ant abundance and richness. Functional group response was calculated to reveal any potential cascading effects correlated to odorous house ant presence or habitat influence. Functional group assemblages revealed significant differences between habitat types. Total ant species decreased from 28 to 18 when comparing natural and urban habitats. Odorous house ant presence correlates to a further reduced urban richness of 7 total species. The average number of non-T. sessile ant nests in urban habitat correlated to a 79.8% decrease with T. sessile present. Resulting ant community dynamics associated with habitat influence and odorous house ant presence leads us to believe that T. sessile initially reaps a benefit as “passengers” of ecological change. Flexible life history traits enable odorous house ant within urban environments to transition into supercolonies whereby they become “drivers” of ecological change. Passenger and driver descriptors can be applied to odorous house ant throughout different phases of their urban invasion. Time or invasion progress be considered when assigning an ecological role to other invasive ants if resources are to be properly allocated to combat their spread. To better prevent T. sessile invasions, I examined odorous house ant response to varying abiotic and biotic conditions. Colony survival and growth was measured for 14 weeks under hot, cold, dry, and humid conditions. Mortality and growth was measured for 71 days for colonies provisioned with differing resource availability including water, food, and brood. Unfavorable biotic conditions appeared more devastating and limiting to colony growth than severe abiotic conditions. Odorous house ant colonies deprived of food, water, or brood suffered total colony death of 70%, 50%, and 25% respectfully. I remain skeptical of results indicating food is the limiting factor for T. sessile spread because water cannot be completely removed from food resources and may be the true limiting factor. Colonies experiencing lab bench conditions with moderate temperature and humidity achieved the highest survival and growth. Outside of optimal lab conditions, cold and humid colonies suffered the least mortality and experienced the least worker caste growth. Hot and humid colonies produced enough new workers to increase total colony size despite high mortality rates. Results from this abiotic and biotic survival testing will contribute to our knowledge of a native ant turned invasive as well as aid in designing protocols to prevent T. sessile dispersal.
Degree
M.S.
Advisors
Buczkowski, Purdue University.
Subject Area
Ecology|Entomology|Urban planning
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.