Comparison of mitochondrial DNA sequences of seven morphospecies of black flies (Diptera: Simuliidae)

Abstract

Universal primers constructed from the 16S ribosomal RNA gene in the Drosophila yakuba mitochondrial genome were successfully used to amplify, via the polymerase chain reaction, the homologous region of mitochondrial DNA from seven black fly morphospecies. Amplification was achieved from single larval salivary glands and from single adults preserved in Carnoy's fixative (ethanol - acetic acid, 3:1), allowing DNA sequences and polytene chromosome banding pattern data to be gathered from the same individuals. Nucleotide sequences of the amplified DNA segment (347 base pairs) were obtained from all the species examined. As in Drosophila, the nucleotide base composition of the sequenced segment from black flies had a high adenine (A) and thymine (T) content (A + T on average comprised 77% of all nucleotides.). Nucleotide differences among the seven species were observed at 59 positions (55 nucleotide substitutions and 4 deletions). There were more transversion differences than transition differences both among and within genera; the proportion of transversions was higher between genera than within genera. Most transversion differences were A----T type, comprising 79% of all transversion differences and 50% of all sequence differences. Phylogenetic inference based strictly on transversion differences confirmed traditional generic and tribal groupings, i.e., Prosimulium fuscum (Syme & Davies) is close to Prosimulium magnum (Dyar & Shannon); Simulium decorum (Walker), Simulium venustum s.l. (Say), and Simulium vittatum s.l. (Zetterstedt) are close to each other; Stegopterna mutata (Malloch) and Cnephia dacotensis (Dyar & Shannon), which belong to the tribe Cnephiini, are grouped together.