Revision of the Merodon serrulatus group (Diptera, Syrphidae)

Abstract

The phytophagous hoverfly genus <i>Merodon</i> Meigen, 1803 (Diptera, Syrphidae), which comprises more than 160 species distributed in Palaearctic and Afrotropical regions, can be differentiated into multiple groups of species that harbor high levels of hidden diversity. In this work, the <i>serrulatus</i> species group of <i>Merodon</i> is revised, providing an illustrated key to species, a detailed discussion on the taxonomic characters and a morphological diagnosis, including also the first data about the preimaginal morphology of this species group. The study includes characteristics of the 13 species of the <i>M. serrulatus</i> group, along with the available distributional data. Moreover, descriptions are provided for seven new species, namely <i>M. defectus</i> Vujić, Likov & Radenković <b>sp. nov.</b>, <i>M. disjunctus</i> Vujić, Likov & Radenković <b>sp. nov.</b>, <i>M. medium</i> Vujić, Likov & Radenković <b>sp. nov.</b>, <i>M. nigrocapillatus</i> Vujić, Likov & Radenković <b>sp. nov.</b>, <i>M. nigropunctum</i> Vujić, Likov & Radenković <b>sp. nov.</b>, <i>M. opacus</i> Vujić, Likov & Radenković <b>sp. nov.</b>, and <i>M. trianguloculus</i> Vujić, Likov & Radenković <b>sp. nov.</b> In addition, the taxa <i>M. serrulatus</i> (Wiedemann in Meigen, 1822), <i>M. bequaerti</i> Hurkmans, 1993, <i>M. hirsutus</i> Sack, 1913, <i>M. kawamurae</i> Matsumura, 1916, <i>M. sacki</i> (Paramonov, 1936) and <i>M. sophron</i> Hurkmans, 1993 are redefined and redescribed. Following a detailed study of the type material sourced from different entomological collections, the status of all available taxa related to <i>M. serrulatus</i> is revised and a new synonymy is proposed: <i>M. tener</i> Sack, 1913 <b>syn. nov.</b> (junior synonym of <i>M. serrulatus</i>). The identity of <i>M. trizonus</i> (Szilády, 1940) could not be assessed as the type specimens are lost. Thus, the name <i>M. trizonus</i> is considered as <i>nomen dubium</i>. The monophyly and composition of this species group are assessed through Maximum Parsimony and Maximum Likelihood analyses of the mitochondrial COI and nuclear 28S rRNA gene sequences.