Physiological innovation and the evolutionary elaboration of courtship behaviour

Biologists have long been fascinated by the elaborate courtship displays performed by diverse organisms throughout the animal kingdom. The evolution of courtship behaviour often requires specializations of neural, sensory and motor systems. In addition, physically impressive displays may also require optimized metabolic, respiratory and cardiovascular systems to sustain the neuromuscular demands. Hormonal signalling can reach all of these tissues simultaneously to prepare them for use in courtship. Studies of male golden-collared manakins, Manacus vitellinus, a small bird of the Neotropics with a physically intense and noisy courtship display, have uncovered numerous androgen-dependent neuromuscular and metabolic specializations that enable not only the performance of elaborate courtship routines, but also their evolutionary exaggeration. However, physiological specializations for one function can create limits on their use for other purposes. Such trade-offs may influence the way courtship develops but may also provide information used by females for mate choice. We review this body of work with an eye towards expanding our appreciation of the evolution of widespread tissue hormone sensitivity and hormone action as the system through which elaborate courtship behaviours evolve.