An integrative approach in the assessment of species delimitation and structure of the Merodon nanus species group (Diptera: Syrphidae)

Unveiling the Mainland vs. Insular Variability of the Eumerus barbarus Species Group (Diptera: Syrphidae) in the Western Mediterranean Basin

Comprising nearly 300 described species, Eumerus Meigen, 1822, is one of the most speciose syrphid genera worldwide, and its taxonomic diversity is remarkable in the Mediterranean basin. The Eumerus barbarus (Coquebert, 1804) group consists of four species in the western Mediterranean. Although the phenotypic variability of this species group has been commented on in previous studies, it has never been contrasted with molecular data. In the present work, the morphological variation found in 300+ specimens of this species group from the western Mediterranean is explored and tested against the COI mitochondrial DNA (mtDNA). The highest phenotypic disparity was found in E. barbarus and Eumerus sulcitibius Rondani 1868. The integrative approach has not revealed cryptic diversity within the species E. barbarus but in E. sulcitibius. As a result, a new species close to E. sulcitibius was discovered, Eumerus sardus Aguado-Aranda, Ricarte & Hauser sp. n., from Sardinia, Italy. The new insular species is here described, illustrated, and discussed. A total of twenty-three haplotypes of COI mtDNA were identified amongst the analyzed Mediterranean specimens of E. barbarus, whereas two and five haplotypes were distinguished in the Iberian specimens of E. sulcitibius and Eumerus gibbosus van Steenis, Hauser & van Zuijen, 2017, respectively. Moreover, the first known barcodes of E. gibbosus and Eumerus schmideggeri van Steenis, Hauser & van Zuijen, 2017 were obtained, and the distribution ranges of all species are mapped. An updated dichotomous key to the males of the E. barbarus group from the western Mediterranean is provided.

The Extraordinary Diversity of Merodon avidus Complex (Diptera: Syrphidae)-Adding New Areas, New Species and a New Molecular Marker

In this paper, the Merodon avidus (Diptera, Syrphidae) species complex was revised, whereupon we discovered and described four new species for science: Merodon atroavidus Vujić, Radenković et Likov sp. nov., M. magnus Vujić, Kočiš Tubić et Ačanski sp. nov., M. nigroscutum Vujić, Radenković et Likov sp. nov. and M. pseudomoenium Vujić, Kočiš Tubić et Ačanski sp. nov. An integrative taxonomy approach was used to delimit species boundaries. Two molecular markers (the mitochondrial COI gene and nuclear 28S rRNA gene-newly analysed marker for the complex) and geometric morphometry of the wing shape, together with morphological data and distribution, successfully separated all species from the complex. The morphological variability of the analysed species is described and discussed and an illustrated diagnostic key for typical morpho-forms of species from the M. avidus complex is presented. A distribution map of all investigated species from the complex is provided. The level of endemicity of the M. avidus complex was discussed.

Integrative taxonomy of the Merodon aberrans (Diptera, Syrphidae) species group: distribution patterns and description of three new species

In this paper, we revise the Merodon aberrans species group of the genus Merodon Meigen, 1803 (Diptera: Syrphidae), providing morphological diagnoses and descriptions, molecular data for three species, as well as an illustrated key and a discussion of the different taxonomic characters used. We also discuss distribution patterns for this species group. The results revealed that the M. aberrans group is composed of five described species (M. aberrans Egger, 1860, M. brevis Paramonov, 1926, M. flavitibius Paramonov, 1926, M. hamifer Sack, 1913, and M. warnckei Hurkmans, 1993) and three new ones, namely M. hermonensis Vujić, Radenković et Likov sp. nov., M. petiolatus Vujić, Radenković et Rojo sp. nov., and M. retectus Vujić, Radenković et Likov sp. nov. Following a detailed study of the type material in different entomological collections, the status of several species is revised, one new synonym is proposed (subspecies M. aberrans isperensis Hurkmans, 1993 as junior synonym of M. flavitibius), lectotypes are designated for M. kneri Mik, 1867 and M. flavitibius, and paralectotypes are designated for M. hamifer and M. flavitibius. Seven out of eight species from the M. aberrans group are distributed in the Asian continent, namely all Caucasian countries, Turkey and Iran, confirming the notion about high diversity of Merodon species in these regions, but also highlighting the need for a systematic faunistic research.

Taxonomic complexity in the genus Merodon Meigen, 1803 (Diptera, Syrphidae)

The genus Merodon Meigen, 1803 is distributed across the Palaearctic and Afrotropical Regions. The present work summarizes the knowledge from recent taxonomic and systematic revisions and includes an identification key for the five monophyletic lineages (namely albifrons, aureus, avidus-nigritarsis, desuturinus and natans), 24 species groups, two species subgroups and 10 unplaced species, along with diagnosis and illustrations. A list of 234 taxa, including 194 described and 40 undescribed species, is appended. Most of the species are distributed in the Palaearctic (209 taxa, 181 described), while 27 species (14 described) are known from the Afrotropical Region. Three lineages (aureus, desuturinus and natans) are present in the Afrotropical Region, as well as in the Palaearctic. The Afrotropical melanocerus species group of the desuturinus lineage and the bombiformis species group of the aureus lineage are endemic to the Afrotropical Region, and all other species groups belong to the Palaearctic fauna. The albifrons lineage contains six species groups (albifrons, constans, equestris, geniculatus, ruficornis and rufus) and two unplaced taxa. The aureus lineage includes five species groups (aureus, bombiformis, funestus, nanus and spinitarsis). The avidus-nigritarsis lineage is divided into 10 species groups (aberrans, aurifer, avidus, clavipes, fulcratus, italicus, nigritarsis, pruni, serrulatus and tarsatus) and eight unplaced taxa. The desuturinus lineage contains two species groups: the Afrotropical melanocerus group, with the melanocerus and planifacies subgroups plus the species M. cuthbertsoni Curran, 1939, and the Palaearctic murorum species group. The natans lineage consists of the natans species group plus the species M. segetum Fabricius, 1794.

Hide-and-seek with hoverflies: Merodon aureus – a species, a complex or a subgroup?

In order to disentangle the currently confused interpretations and nomenclature of Merodon aureus and M. aeneus, we have reviewed all existing type material and species names known to us as assigned synonyms of these taxa. We resolve M. aeneus as being a junior synonym of M. aureus. We designate a lectotype for M. aureus and a neotype for M. aeneus. Additionally, we provide evidence that M. aureus, together with two newly discovered taxa (M. calidus sp. nov. and M. ortus sp. nov.), represent a complex of cryptic species named the M. aureus species complex. This complex, together with the M. unicolor species complex and the species M. pumilus, is part of the M. aureus subgroup. The M. unicolor species complex comprises two cryptic species: M. unicolor and M. albidus sp. nov. The new species are described by applying an integrative taxonomic approach using several data types (COI and 28S rRNA genes, geometric morphometry of the wings, ecological and distributional data). Based on the COI gene sequence analysis and distributional data, the pupa previously described as an immature stage of the species M. aureus is redefined as an immature stage of the new species M. calidus. Speciation within the M. aureus subgroup is discussed in the context of the phylogeographic history in the studied region.

Checklist of hover flies (Diptera, Syrphidae) of the Republic of Georgia

A checklist of the Syrphidae species of the Republic of Georgia is presented. New hover fly (Diptera: Syrphidae) records from Georgia are provided as a result of field work conducted in 2018. At the same time, published syrphid records for the country are here reviewed and updated. A total of 357 species of hoverflies are now documented from Georgia, 40 of which are reported for the first time. Moreover, DNA barcodes were sequenced for 238 specimens, representing 74 species from this country.

Revision of the Merodon serrulatus group (Diptera, Syrphidae)

The phytophagous hoverfly genus Merodon 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 serrulatus species group of Merodon 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 M. serrulatus group, along with the available distributional data. Moreover, descriptions are provided for seven new species, namely M. defectus Vujić, Likov & Radenković sp. nov., M. disjunctus Vujić, Likov & Radenković sp. nov., M. medium Vujić, Likov & Radenković sp. nov., M. nigrocapillatus Vujić, Likov & Radenković sp. nov., M. nigropunctum Vujić, Likov & Radenković sp. nov., M. opacus Vujić, Likov & Radenković sp. nov., and M. trianguloculus Vujić, Likov & Radenković sp. nov. In addition, the taxa M. serrulatus (Wiedemann in Meigen, 1822), M. bequaerti Hurkmans, 1993, M. hirsutus Sack, 1913, M. kawamurae Matsumura, 1916, M. sacki (Paramonov, 1936) and M. sophron 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 M. serrulatus is revised and a new synonymy is proposed: M. tener Sack, 1913 syn. nov. (junior synonym of M. serrulatus). The identity of M. trizonus (Szilády, 1940) could not be assessed as the type specimens are lost. Thus, the name M. trizonus is considered as nomen dubium. 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.

Conflict and congruence between morphological and molecular data: revision of the Merodon constans group (Diptera : Syrphidae)

We revise the Merodon constans species group of the genus Merodon Meigen, 1803 (Diptera: Syrphidae), provide morphological diagnosesand descriptions, as well as an illustrated key and a discussion on the different taxonomic characters used. In total, 15 species were studied, their geographic distributions are presented on maps, and nine new species are described. Two species are redefined and neotypes are designated, lectotypes are designated for five species, and onespeciesis reinstated as valid. Following a detailed study of type material in different entomological collections, the status of several species is revised and three new synonymies are proposed. The M. constans species group was resolved as being monophyletic within the M. albifrons lineage based on molecular analyses using COI and 28S rRNA gene sequences. Three species morphologically similar to M. constans (Rossi, 1794) but occurring outside its distributional rangewere supported as being valid and distinct species on the basis of molecular data, but they were not distinguishable based on morphological characters. By contrast, continental populations of M. analis Meigen, 1822 could not be separated from Mediterranean M. constans based on differences in COI or 28S rRNA genes. The same molecular markers could not discriminate between two other species pairs. We conclude that these molecular markers only partially resolve species within the M. constans group. Geometric morphometry of wing shape successfully separated M. analis and M. constans, as well as M. spineus Vujić, Šašić Zorić & Likov, sp. nov. in both species and population analyses.