Subset partitioning of the ribosomal DNA small subunit and its effects on the phylogeny of the Anopheles punctulatus group

A phylogenetic study, based on maximum parsimony, of ten species in the Ano pheles punctulatus group of malaria vectors from the south-west Pacific was performed using structural and similarity-based DNA sequence alignments of the nuclear small ribosomal subunit (SSU = 18S). The structural alignment proved to be more informative than a computer generated similarity-based al ignment. Analyses involving the full structural sequence alignment (2169 bp ) and the helical regions (1547 bp) resolved a single tree of the same topo logy, while analyses using the similarity based alignment could not resolve the group. Studies on the three structural domains of the nuclear rDNA SSU identified domain 2 (769 bp) as the only region informative at the sibling -species level and resulted in the same tree as the full structural sequenc e and helical regions. The main conclusions of these studies were that the An. punctulatus group formed two clades: a Farauti clade containing members displaying an all black scaled proboscis (An. farauti 1-3 and 5-7) and a P unctulatus clade containing members that display some degree of white scali ng on the proboscis (An. farauti 4, An. punctulatus and An. species near pu nctulatus). Anopheles koliensis can display either proboscis morphology and was positioned basal to the Farauti Clade. These results do not fully conc ord with those derived from the mitochondrial COII gene.