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Genomic DNA fragments from males of Psychodopygus wellcomei were isolated and shown to be useful as sensitive diagnostic probes for positively separating individuals of this species from those of Ps. complexus. These two members of the Ps. squamiventris series are found sympatrically in foci of cutaneous leishmaniasis in the hill forests of southern Pará State. Of the two species, only Ps. wellcomei is thought to be an important vector of Leishmania braziliensis sensu stricto, but this is based on circumstantial evidence because of the difficulties of identifying female sandflies within the series. The diagnostic probes were isolated from a library of Ps. wellcomei built by ligating short fragments of Sau 3A-restricted, genomic DNA into the plasmid vector pUC 18. Differential screening of 1316.library clones with total genomic DNA of Ps. wellcomei and Ps. complexus identified 5 recombinants, with cross-hybridizing inserts of repetitive DNA, that showed strong specificity for Ps. wellcomei. As little as 0.4% of the DNA extracted from an individual sandfly (= ca. 0.5 nanograms) was specifically detected. The diagnostic probes were used to identify as Ps. wellcomei a wild-caught female sandfly found infected with L. braziliensis s.s., providing only the second positive association between these two species.

The evolutionary relationships of sand flies and Leishmania are discussed in this report, which draws distinctions between co-association, co-evolution and co-speciation (or co-cladogenesis). Examples focus on Phlebotomus vectors of Le. infantum and Le. major in the Mediterranean subregion.

Popular classes of microsatellites are not always abundant in insects or easily isolated from them. Dotblot hybridizations demonstrated much variation in the relative abundance of four repeat classes in four phlebotomine sandfly species. Only AAT-class repeats were specifically isolated from a phagemid library of Lutzomyia whitmani, even though other microsatellites had similar abundances. An enrichment step would have targeted classes but was omitted because relatively long flanking sequences were sought. All fourteen sandfly loci had a non-coding structure, and a minority of dipteran AAT-class repeats found in DNA databases and the literature were from exons. Therefore, this class should often provide neutral alleles for population studies. Perfect, not imperfect, AAT-class repeats were polymorphic in wild L. whitmani.