Rapid female multiple mating in red flour beetles (Tribolium castaneum)

Abstract

Many female insects mate with multiple males within a single fertile period despite costs such as expenditure of energy and time and contraction of sexually transmitted diseases. In the red flour beetle, Tribolium castaneum, females remate with different males within minutes of the first copulation. If rapid multiple mating is adaptive then multiply mated females should have higher fitness than singly mated females. In this study, we determined the remating frequency of female beetles, characterized female mating behavior, and examined the fitness consequences of female multiple mating. We found that female T. castaneum mated, on average, with 4–6 nonvirgin males within a 1-h observation period. The number of males present in a mating arena did not significantly affect copulation frequency or the intermating interval. However, number of males present significantly affected the length of a single copula as a result of disturbance by rival males when more males were present. Female mating with multiple males in 24 h did not significantly improve egg production, F1-adult production, egg-to-adult viability, fertility retention, and female survivorship. Thus, multiple mating did not enhance long-term female fitness. Polyandrous mating behavior may have evolved through other mechanisms such as fertility assurance and increased offspring genetic diversity or fitness.