Abstract
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.
Highlights
Known as flower flies or hoverflies, syrphids (Diptera: Syrphidae) are distributed worldwide, absent only in remote oceanic islands and Antarctica (Thompson & Rotheray, 1998)
The same groupings and the same inferred relationships were found in the present analysis with a minor nomenclatural change: Platycheirus concinnus (Snow, 1895) appears as Platycheirus pictipes (Bigot, 1884) following the synonymy proposed by Young et al (2016b)
The novelty in the present study is the placement of the new species without metasternal excavation, Melanostoma janeceki sp. nov., as sister-group of Afrostoma quadripunctatum [= Melanostoma quadripunctatum comb. nov. in fig. 1] with the highest Bayesian posterior probability
Summary
Known as flower flies or hoverflies, syrphids (Diptera: Syrphidae) are distributed worldwide, absent only in remote oceanic islands and Antarctica (Thompson & Rotheray, 1998). Vockeroth (1969) divided the subfamily Syrphinae into six tribes, namely Bacchini, Melanostomini, Paragini, Toxomerini, Chrysotoxini and Syrphini. Vockeroth (1992) rearranged his tribal system with the currently accepted four tribes: Bacchini, Paragini, Toxomerini, and Syrphini. This current tribal classification of Syrphinae needs a revision based on recent molecular studies, where Bacchini and Syrphini were never resolved as monophyletic (Mengual et al, 2008a, 2012, 2015; Mengual & Thompson, 2011; Mengual, 2015; Young et al, 2016a; Pauli et al, 2018)
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