Tapinoma sessile, otherwise known as the "odorous house ant," is found widely within the United States. These little critters generally aren't aggressive, but because they'll eat just about any food in your house, and are able to establish a colony virtually anywhere, they can sometimes be a bit of a nuisance.
Since we see ants all the time, it's easy to not realize how surprising it is that any critter can adapt so well to life in urban areas. Although ants have evolved over many years to survive in natural environments, Tapinoma sessile can nevertheless thrive in urban environments.
Sean Menke (North Carolina State University) and coworkers have begun to ask how these ants have established themselves in urban environments. This question is relevant towards understanding and controlling the establishment of invasive species.
Multiple independent urban establishments.
The scientists collected ants from nearly fifty discontinuous locations (minimizing the complication of geographic transition zones) throughout the United States, from both urban and natural habitats. They found that Tapinoma sessile ants are comprised of at least four genetically-distinct populations.
Genetic differences within a population were low, but present. This suggests that each of the four populations represents a unique lineage of ants.
This is turn is strong evidence that Tapinoma sessile has not become established in urban habitats as a result of one introduction and dispersal event. These ants have most likely established themselves independently at least several times from natural habitats.
Is there a trait that has facilitated this outcome? The scientists note that different colonies can have very different numbers of total ants and queens, suggesting that Tapinoma sessile is able to adapt its colony structure to local conditions.
More specifically, these ants can form huge colonies in urban environments, sometimes exceeding millions of ants. The scientists speculate that this might help them to survive in the patchy environment common in urban areas.
Originating from natural habitats, Tapinoma sessile ants have most likely established themselves multiple times within United States urban areas. Even one adaptation is rare among most species.
Future research should address the behaviors and social structure that enables these ants to thrive in both urban and natural environments. Such knowledge may help scientists control the establishment of invasive species, and possibly promote the retention of native species.
for more information:
Menke, S. B., Booth, W., Dunn, R. R., Schal, C., Vargo, E. L., & Silverman, J. (2010). Is It Easy to Be Urban? Convergent Success in Urban Habitats among Lineages of a Widespread Native Ant PLoS ONE, 5 (2) DOI: 10.1371/journal.pone.0009194