Increased calling rate drives increased pheromone emission in domesticated Queensland fruit fly males.

Domestication can change many aspects of insect life history and reproductive biology. In Queensland fruit fly (Q-fly), males of colonies maintained longer under laboratory conditions release more pheromone. Still, it is unknown if this change arises from increased pheromone production or increased calling effort. Q-fly males disperse pheromone by transferring it from rectal glands to wings and body, followed by rapid wing fanning that produces audible 'calling songs'. We compared a young and an old colony from the same region (8 and 28 generations, respectively) for the amount of pheromone released, the amount produced in rectal glands, and the characteristics of calling songs. Our results agree with previous studies, reporting that males from the old colony released more pheromone than males from the young colony. No significant difference between the colonies was found in the amount of pheromone in the rectal glands. While calling probability, total daily call duration, pulse train duration, pulse train interval, and pulse train period did not differ between the colonies, male Q-flies from the old colony had higher calling rate (pulses per minute) than those from the young colony. Increased pheromone release of domesticated male Q-flies is best explained by increased investment in calling songs that disperse the pheromone.