RESEARCH: Mechanisms of Success in Biological Invasions

A major challenge of invasion biology lies in the development of a predictive understanding of invasion processes.  Attempts to identify the proximate causes of invasion success or to predict rates of spread seldom emphasize behavioral characteristics. Recent work, however, illustrates that insight into the proximate causes of animal invasions often hinges upon a careful assessment of behavioral mechanisms. In addition, invasions can provide an opportunity to test the factors that influence the maintenance of specific behavioral repertoires. Our work on Argentine ant invasions has shown that behavioral attributes, specifically a loss of territorial behavior associated with reduced intraspecific aggression, may contribute to their success as invaders. Ant colonies typically have well-defined territorial boundaries, a condition referred to as multicoloniality. Multicolonial ants defend their territories aggressively, particularly against conspecifics. Such territorial behavior is thought to limit population density in ants, and for animals generally, because territorial defense can increase mortality and expends resources, time, and energy that could otherwise be allocated to growth, maintenance and reproduction. However, many invasive ant species exhibit a colony structure known as unicoloniality where levels of intraspecific aggression are reduced, colony boundaries are weak to non-existent, and supercolonies composed of networks of interconnected nests are the norm. Worker populations of unicolonial ants often attain higher densities than those of multicolonial ants, perhaps because unicolonial species are exempt from the costs of defending territories against conspecifics. My future research will examine how changes in the biology of invaders work in concert with both biotic factors (such as the absence of coevolved natural enemies and competitors) and abiotic factors (such as local conditions, specifically temperature and water availability) to determine their success.

• Impacts of biological invasions
• Patterns and mechanisms of nestmate recognition in social insects
• How different animal taxa respond to habitat fragmentation