SMALL-SUBUNIT RIBOSOMAL-RNA GENES OF TABANIDS AND HIPPOBOSCIDS (DIPTERA, BRACHYCERA) - EVOLUTIONARY RELATIONSHIPS AND COMPARISON WITH OTHERDIPTERA

The small subunit ribosomal RNA (SSU rRNA) genes of hippoboscid (Ornit hoica vicina Walker) and tabanid (Chrysops niger Macquart) Diptera wer e sequenced to determine their phylogenetic position within the order and to determine whether or not extensive hypervariable regions in thi s gene are widespread in the Diptera A parsimony analysis of an alignm ent containing 8 dipteran sequences produced a single most parsimoniou s tree that placed O. vicina as sister group to Drosophila melanogaste r-Meigen. The tabanid Chrysops nige, was sister group to the asilomorp han taxa, and the sister group to the Brachycera was a Tipula sp. alth ough this relationship was not supported by bootstrap analysis. The hi ppoboscid and tabanid sequences contain extensive hypervariable region s in the V2, V4, V6, and V7 regions as do other Diptera. When these re gions of the alignment were excluded from the phylogenetic analysis, a single most parsimonious tree was found. This tree had an identical o verall topology to the tree obtained from the total data set. The hype rvariable regions in parts of the dipteran SSU rRNA genes were more ex tensive in the nematocerous dipteran sequences used in this study than in the other dipteran representatives; these hypervariable regions ma y be of more utility in inferring relationship among species and subsp ecies than at the suprageneric level.