Variation in adult sex ratio alters the association between courtship, mating frequency and paternity in the lek-forming fruitfly Ceratitis capitata.

The intensity with which males deliver courtship and the frequency with which they mate are key components of male reproductive success. However, we expect the strength of the relationship between these traits and a male’s overall paternity to be strongly context dependent, e.g. to be altered significantly by the extent of post-mating competition. We tested this prediction in a lekking insect, Ceratitis capitata (medfly). We examined the effect of manipulating the sex ratio from male- to female-biased (high and low male competition, respectively) on courtship behaviour, mating frequency and paternity of focal males. Under high male competition, focal males delivered significantly more courtship but gained lower paternity than under lower competition. Paternity was positively associated with mating frequency and small residual testes size. However, the association between mating frequency and paternity was significantly stronger under low competition. We conclude that manipulation of sex...