Phylogenetic relationships of the bacchine flower flies (Diptera: Syrphidae) based on molecular characters, with a description of a new species of Melanostoma (Schiner, 1860)

The phylogenetic relationships among the genera of the tribe Bacchini sensu lato (i.e., Syrphinae with simple, unsegmented aedeagus) were inferred using molecular evidence. The mitochondrial protein-coding gene cytochrome c oxidase subunit I (COI) and the nuclear ribosomal 28S and 18S rRNA genes for 54 bacchine taxa were analyzed using Bayesian inference and Maximum Likelihood. Among the analyzed taxa there is a new species of Melanostoma (Schiner) from Cameroon, Melanostoma janeceki Mengual, sp. nov., which is described in full. This new species has a complete metasternum without excavation, a characteristic that is not present in other species of Melanostoma, usually with an excavated metasternum, but it is the diagnostic character of the genus Afrostoma Skevington, Thompson & Vockeroth. Based on the phylogenetic placement of Melanostoma janeceki Mengual, sp. nov. the taxonomic status of Afrostoma as a genus is discussed and a new generic classification of Bacchini stat. rev. and Melanostomini stat. rev. is presented in the light of the inferred phylogeny. Results did not recover Bacchini sensu lato monophyletic, but into two groups as follows: Melanostoma and related genera, and Baccha, Platycheirus and related genera. Pseudoplatychirus van Doesburg is considered junior synonym of Platycheirus Le Peletier & Audinet-Serville, and Afrostoma Skevington, Thompson & Vockeroth as junior synonym of Melanostoma. Pyrophaena Schiner and Eocheilosia Hull comb. nov. are ranked as valid genera, and consequently, the genus Platycheirus is divided into four subgenera: Platycheirus (Carposcalis) (Enderlein), Platycheirus (Pachysphyria) (Enderlein), Platycheirus (Platycheirus), and Platycheirus (Tuberculanostoma) (Fluke) comb. nov.