The expression of testosterone-dependent sexual traits might signal the ability of their bearers to cope with parasite infections. According to the immunocompetence handicap hypothesis (IHH), such signals would be honest because physiological costs of testosterone, such as a reduced ability to...

Traits related to fitness are often pleiotropically linked or otherwise constrained in their expression. Organisms therefore trade between fitness components such as number and viability of their offspring. The physiological mechanisms mediating such trade-offs, however, have been poorly...

The size of the group of social species might influence basic aspects of productivity and social interactions. In many primitively social insects, foundress queens are basically in control of the number of workers in their first brood. We examined factors that might influence the optimal number...