Enzyme polymorphism and genetic variability of laboratory populations of Phlebotomus papatasi, P. bergeroti, P. langeroni, and P. perniciosus

Abstract

Enzyme allomorph frequency and electrophoretic mobility were evaluated to clearly separate between morphologically similar sandfly species and to yield quantitative measures of their genetic similarity. Twelve enzyme systems were studied in laboratory colonies of Phlebotomus perniciosus, P. langeroni, P. papatasi, and P. bergeroti. Phlebotomus perniciosus and P. langeroni confirmed vectors of visceral leishmaniasis, were found to have fixed diagnostic allomorph differences at 3 enzyme loci (ICD-2, FUM, XDH). Phlebotomus papatasi, a known vector of cutaneous leishmaniasis and phleboviruses and P. bergeroti, a newly colonized suspected vector, were clearly differentiated from each other by a fixed allomorph at the MPI locus. Polymorphism at loci in these sandfly colonies ranged from 6.7% (P. perniciosus) to 43.7% (P. papatasi), with lowest levels seen in the older colonies. Expected heterozygosity was highest in P. papatasi, despite 33 generations of inbreeding, and comparable to that of P. bergeroti in its 7th generation. Against a scale of 0 for completely different, and 1.0 for identical genotypes, the enzyme data yielded indices of genetic identity (I) between P. perniciosus and P. langeroni and between P. papatasi and P. bergeroti of 0.783 and 0.737, respectively. These relatively high levels of genetic identity, paralleling similarities between species in morphology, inbreeding compatibility, and vectorial attributes, provide evidence of comparable and recent evolutionary divergence.