The Evolution of Cooperative Breeding Among Ant Queens
The ant Messor pergandei of the desert southwest provides a unique system to study the evolution of cooperation, conflict, and cooperative breeding. In one region of the species' range, queens are intolerant of others and always start new colonies alone, while in another, new colonies are initiated by groups of unrelated queens. Within the cooperative region, there is geographic variation in the duration and degree of cooperation. We exploit this variation and use a variety of field and laboratory studies to test hypotheses predicting the evolution of cooperative breeding from a non-cooperative state. This research is a group effort with my collaborator Sara Helms Cahan and graduate student Nate Newman. It is currently supported by the National Science Foundation.
Our research on invasive species focuses on an important invader of the southeastern United States, the red imported fire ant, Solenopsis invicta. Honeydew produced by a species of invasive mealybug can be exceptionally important to the nutrition of this ant, and our research suggests that the success of the fire ant may be facilitated by the mealybug, and thus indirectly by the availability of the mealybug's host plants (grasses). The most important of these grasses are themselves introduced species which are encouraged by agriculture and widespread throughout the southeastern United States. Our research aims to determine the specific nature of interactions among the ants, mealybugs, an grasses, and to determine how those interactions influence the size of fire ant populations. This research has been supported by the National Research Initiative of the USDA. A story on this research was aired on National Public Radio's Morning Edition. Click here to listen.
Evolution of Sex Allocation
One of the most striking observations on sex allocation in ants is the common occurrence of colony sex ratio specialization, where the reproductive broods of some colonies consist of primarily or exclusively males, while the reproductive broods of others consist of primarily or exclusively females. My research on sex allocation is mostly concerned with understanding why such specialization occurs, particularly in cases where it is not predicted by existing theory. Empirical research has ranged from studies on ants in the genus Pheidole in the southwestern United States, to studies on ants in the genus Formica in Switzerland, the latter in collaboration with Laurent Keller and Rolf Kümmerli (University of Lausanne). In collaboration with Max Reuter (University College London) and Laurent Keller, we have developed mathematical models of queen-worker conflict that may provide new insight into the causes of sex ratio specialization in the social Hymenoptera.