Cotesia flavipes Cameron and Cotesia sesamiae (Cameron) (Hymenoptera : Braconidae) do not exhibit complementary sex determination : Evidence from field populations

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Diploid males are expected to occur in populations of some Hymenoptera because of the single-locus complementary sex determination (sl-CSD) mechanism. If sl-CSD is found in a species that produces gregarious broods and sib mates at a high frequency, a fraction of these sib-matings (matched mating) produces diploid male offspring. We developed models to predict the matched mating frequency in populations with different frequencies of sib mating and egg fertilization. The predictions of these models are used to determine if we can use the distributions of brood sex ratio and brood size to determine if a species has sl-CSD. The models show that sl-CSD can be detected from these brood sex ratios if the diploid male offspring survives. We applied our models to Cotesia sesamiae and its exotic congener Cotesiaflavipes (Hymenoptera : Braconidae), to determine if sl-CSD occurs in these species. Parasitoids were reared from stemborer larvae sampled from maize fields in Kenya between 1992 and 1999. We found no evidence for the presence of sl-CSD with survival of diploid males in both braconid species, but we cannot exclude the possibility that sl-CSD with diploid male mortality takes place in these species.
2004-11-25