Taxonomic assessment of Anopheles crawfordi and An. dangi of the Hyrcanus Group of subgenus Anopheles in Vietnam

Anopheles dangi, introduced as a new species of the Hyrcanus Group of subgenus Anopheles in an illustrated dichotomous key for the identification of the Anopheles mosquitoes of Vietnam published in 1987, was distinguished from Anopheles crawfordi based on the presence of a humeral pale spot on the base of the costal vein of the wing. However, this character has been known to occur occasionally in An. crawfordi. To determine whether An. dangi is distinct from An. crawfordi, we analyzed nucleotide sequences of the COI, COII and Cyt-b genes of mtDNA and the D3 gene of rDNA obtained from specimens collected in south-central Vietnam that were identified as An. dangi and An. crawfordi based on the presence or absence, respectively, of a humeral pale spot. Maximum Likelihood and Bayesian analyses of the sequences showed a low mean genetic distance of 0.004 for specimens identified as An. crawfordi and 0.008 for those identified as An. dangi. The mean genetic distance between the two nominal species was 0.006, compared with 0.077 for any group versus the outgroup taxa Anopheles dirus and Anopheles minimus, and the specimens of the two forms clustered in a single strongly supported clade. Consequently, An. dangi is merely a morphological variant of An. crawfordi and is deemed to be a synonym of that nominal species.