Multiple Mating in Harvester Ants

In most species of social insects, the queen mates once; western harvester ants (Pogonomyrmex occidentalis) are unusual, in that the single queen mates with 7 - 10 males. Therefore the workers of a colony consist of many genetically distinct offspring (patrilines). Because multiple mating is presumed to be costly to females, multiple mating must increase female fitness in order to evolve. Our field studies have shown that colonies with higher levels of genetic diversity grow faster, survive longer, and reproduce more than colonies with low levels of genetic diversity (for details, see the Harvester Ant Website at http://home.bchs.uh.edu/~bcole/pogo/. We are examining how increased genetic diversity of a colony’s workers improves colony fitness. We use a combination of field studies in western Colorado and lab studies at UH to measure the effect of genetic diversity on important colony-level behaviors such as temporal activity, foraging and responses to infected nest mates.

Sexual Selection and Genetic Conflict

In ants, because of haplodiploid sex determination, males only contribute genetically to daughters, but not to sons, which are produced solely by the queen. As a consequence, there may be conflict between males and queens over how sperm is allocated to workers versus queens, which are typically a fraction of all the females produced in the colony.

Wing Pattern Evolution in Butterflies

I am still interested in the role of sexual selection and female choice in the evolution of butterfly wing patterns. Pierid butterflies are an excellent experimental system for these questions, because their wing phenotypes can easily be manipulated, enabling field tests of mate choice.