Hybridization experiments of the Anopheles dirus complex

Abstract

The Anopheles dirus is a complex of sibling species which have been discovered recently based mainly on analyses of chromosomes and cytogenetic investigation. However, hybridization experiments are of considerable importance for confirmation of species status. In this study, reciprocal cross-matings between members of the An. dirus complex, selfcrossing and backcrossing of F1 offsprings of some pairs were performed and survival rates of F1 hybrids were tabulated. In some pair-matings, abnormality of reproductive systems of F1 male hybrids and asynapsis in salivary gland polytene chromosomes of some F1 hybrids were demonstrated. Various degrees of genetic incompatibility were found in the crosses between An.balabacensis and An. dirus species A, B, C and D and the crosses between An. dirus E and species A, B, C and D. An. balabacensis seems to be more closely related to species A and C than the others whereas An. dirus E is apparently more closely related to species D than it does to species A, B and C. Both species D and E seem to have close phylogenetic relationship based on the present cytogenetic evidence. These two species could have arisen from a common ancestor.