Interspecific hybridization and genetic variability of Phlebotomus sandflies

The first successful hybridization is reported between Phlebotomus papatasi and P. duboscqi, two important Old World sandfly vectors of leishmaniasis and other diseases. Laboratory strains of P. papatasi and P. duboscqi were separable by six diagnostic enzyme loci: Est-3, Idh-1, Mdh-2, Mpi, Tre-1 an d Tre-3. Hybrids between the two species were verified by the recovery of h eterozygous isozyme patterns for the diagnostic loci. No F-2 or backcross p rogeny were obtained. P. papatasi was separated from P. bergeroti by three diagnostic enzyme loci: Est-3, Mpi and Pgd. The isozyme patterns of P. herg erori contain elements of both P. duboscqi and P. papatasi, although seven diagnostic loci (Est-3, Idh-1, Me, Mpi, Pgd, Tre-1 and Tre-3) separated P. bergeroti from P. duboscqi. Genetic variability profiles of the three speci es were established for 20 enzyme loci. Three geographically distant strain s of P. papatasi from Calcutta, Maharashtra and Israel had isozyme genetic distances of < 0.05. The recently established Calcutta strain showed an une xpectedly low genetic variability with only one (Idh-2) of 20 loci being po lymorphic (average heterozygosity of 1.9 %) in contrast to 5-8 polymorphic loci (10-12 % heterozygosity) in the Maharashtra and Israel strains. Mass a nd single pair crosses between the three P. papatasi strains were fertile w ith normal progeny numbers. Thus we found no signs of speciation in P. papa tasi.