Date of Award
Master of Science (MS)
Committee Member 1
Committee Member 2
Odorous house ants (Tapinoma sessile) are a widespread North American ant species and common nuisance pest. In addition to their pest status, odorous house ants are of interest as a model system for understanding the factors that lead to variable queen number and nesting strategy across ants, as well as possible insight into common traits of exotic invasive (or “tramp”) ant species. While T. sessile is native to North America, in urban environments it forms large supercolonies with many queens and nest sites connected by trails, similar to a variety of exotic invasive ants, most of which are of tropical or subtropical origin.
To determine the extent to which odorous house ants follow patterns of reduced conspecific aggression commonly found in other ant species with similar polygynous colony structures, a variety of behavioral assays were used to assess aggressive behavior between members of colonies from natural and urban environments. For all three assays, urban polygynous colonies were in fact the most aggressive, in contrast to my predictions. While the reasons for higher aggression in urban colonies are not clear, it is possible that the natural colonies of odorous house ants are simply too small to risk losses due to conflict. The extremely large worker populations of urban supercolonies may allow different competitive strategies that were previously impossible for T. sessile to utilize successfully.
While a large proportion of the research on ant behavior and chemical ecology is performed within a laboratory setting, relatively few studies have directly examined the effects of laboratory maintenance on ants. Using a combination of methods from behavioral and chemical ecology, I compared workers that had been maintained in a lab over time to workers freshly collected from the field at a variety of time points. In contrast with previous research on the topic, this study had the added strength of taking several observations in a series over time, rather than simply comparing an initial and final time point. Contrary with those studies, I found no effect of lab maintenance on ant behavior. Cuticular hydrocarbon profiles were significantly altered by laboratory maintenance, however, this effect was small when compared to the differences in cuticular hydrocarbon profiles between colonies. However, given the likelihood of different responses for different species as well as the possibility of stronger effects with longer durations of laboratory maintenance, I encourage others to replicate my method with a broad variety of ant species and conditions.
Taken together, these findings demonstrate that even for well-established patterns in ecology, any given species may deviate from the expectation for a variety of reasons. Continuing to test established theory with a wider range of organisms and conditions will ultimately strengthen our ability to create predictive theory for systems which are not currently as well understood.
Luttermoser, Timothy J., "Nestmate recognition in odorous house ants (Tapinoma sessile): Effects of social plasticity, urbanization, and laboratory maintenance" (2016). Open Access Theses. 791.