Systematics and taxonomy of the ruficornis group of genus Merodon Meigen (Diptera: Syrphidae)

We revise the ruficornis group of species of Merodon Meigen (Diptera, Syrphidae) providing an illustrated key, a discussion of taxonomic characters and a morphological diagnosis. A total of 18 species from the ruficornis group are treated including distributional data. Descriptions are provided for seven new species: M. gallicus Vujić & Radenkovićsp.n., M. hoplitis Hurkmans sp.n., M. lamellatus Vujić & Radenkovićsp.n., M. nigripodus Vujić & Hayat sp.n., M. ovaloides Vujić & Radenkovićsp.n., M. ponticus Vujić & Radenkovićsp.n., and M. turcicus Vujić & Hayat sp.n. The taxon M. auripes Sack, is redefined and a neotype designated. Lectotypes are designated for M. graecus Loew; M. planiceps Loew and M. crymensis Paramonov. The monophyly and systematic position of this species group was assessed based on parsimony and maximum likelihood analyses of mitochondrial COI and nuclear 28S rDNA sequences. A very high level of endemism was observed in the ruficornis species group. Among 18 taxa, 12 are limited‐range endemics, present in few mountain areas or in a small part of the total range of the group. These endemics clearly show the importance of geographic isolation in the process of speciation.