Phylogenetic analysis of the subgenus Himalayum within the genus Simulium s.l. (Diptera: Simuliidae) using mitochondrial 16S rRNA gene sequences

The subgenus Himalayum Lewis within the genus Simulium Latreille s.l. is a small group, including only two species, i.e., S. indicum Becher and S. nigrogilvum Summers, both of which are severe pests on humans at the southern foot of the Himalayas. In this study, the mitochondrial 16S rRNA gene of S. nigrogilvum from Thailand was sequenced and compared with those of other species of related subgenera within the same genus. The molecular phylogenetic analysis showed that this species had a much closer relation with species of Simulium s. str. than with other subgenera such as Cnetha Enderlein, Gomphostilbia Enderlein, Nevermannia Enderlein and Wallacellum Takaoka in the Oriental Region, and was not separated from, but was nested in, species of Simulium s. str. Morphologically, the two Himalayum species are very similar to those of the subgenus Simulium, in particular, to those of the griseifrons species-group within it. It is suggested that the subgenus Himalayum should be treated as a junior synonym of Simulium s. str.