Causes and consequences of male–male courtship in fruit flies

Abstract

The mechanisms maintaining homosexual behaviour in animals are not well understood. In fruit flies, where male–male courtship is prevalent, it has been suggested that young males gain from being courted by mature males, perhaps through learning. I conducted two series of experiments to critically examine why mature males court immature males and what immature males may gain from such courtship. The results indicate that mature males do not identify the sex of the sexually ambiguous immature males and find them attractive even after substantial experience. These findings agree with recent research indicating that males initially court a broad range of potential mating targets and then narrow their courtship focus based on their experience of being rejected by classes of flies such as recently mated females or heterospecific females, which are clearly identified by their distinct pheromonal profiles. Compared to inexperienced males, males that either had received courtship when immature or had been housed with mature males when young did not have either higher mating frequencies or shorter mating latencies but spent more time courting females. Such higher courtship intensities may translate into a mating advantage in some settings. It appears that young males that interact with mature males develop into a sexually aggressive phenotype, which could better prepare them to compete for females.