MOLECULAR-IDENTIFICATION OF SYMPATRIC CHROMOSOMAL FORMS OF ANOPHELES-GAMBIAE AND FURTHER EVIDENCE OF THEIR REPRODUCTIVE ISOLATION

Three chromosomal forms of Anopheles gambiae s.s., designated as Bamak o, Mopti and Savanna, were studied for diagnostic PCR assays based on the analysis of the X-linked ribosomal DNA (rDNA). The study was perfo rmed on a 1.3 kb fragment containing part of the 28S coding region and part of the intergenic spacer region, The amplified material was cut with fourteen restriction enzymes to detect Restriction Fragment Lengt h Polymorphisms (RFLPs). The enzymes Tru9I and HhaI produced patterns of DNA bands which differentiated Mopti from Savanna and Bamako; moreo ver, a distinct 'hybrid' pattern was recognized in the Fi female proge ny from the cross of Mopti with either one of the other two chromosoma l forms, The diagnostic significance of the PCR-RFLP assay was verifie d on 203 karyotyped females from field samples collected in two villag es in Mall and one village in Burkina Faso. Agreement was observed bet ween the chromosomal and the molecular identifications. No 'hybrid' mo lecular patterns were detected even among carriers of rare heterokaryo types hypothetically produced by crosses between Mopti and Savanna, Th e results confirm previous observations indicating barriers to gene fl ow within An. gambiae s.s. and supporting the specific status of the t axonomic units proposed on cytogenetic ground.