# Déjà Vu in Merodon Taxonomy (Diptera: Syrphidae): Unveiling Hidden Species Inside Merodon caudatus and M. ottomanus Taxa

## TL;DR

This paper discovers and describes five new hoverfly species within two existing species groups using a combination of morphological, genetic, and shape analysis methods.

## Contribution

The study introduces five new species within the Merodon genus using an integrative taxonomic approach.

## Key findings

- Five new species were identified within the Merodon caudatus and M. ottomanus groups.
- Genetic analysis confirmed the distinctiveness of the new species.
- Wing shape differences supported the validity of three new species.

## Abstract

The remarkable diversity and species richness of the Merodon avidus–nigritarsis lineage has been further expanded with the discovery of five new species, which were distinguished using an integrative approach including traditional adult morphological characteristics, molecular analysis, and geometric morphometrics.

Two new species groups within the avidus-nigritarsis lineage of the hoverfly genus Merodon Meigen are here defined and assessed, i.e., the Merodon caudatus and Merodon ottomanus groups. Within the M. caudatus group, two species are recognised:Merodon caudatus Sack and a new species, Merodon crispotarsus sp. nov. Within the M. ottomanus group, an extensive examination of material from different collections revealed the presence of four new species, Merodon auriolus sp. nov., Merodon paeninsula sp. nov., Merodon projectus sp. nov., and Merodon rostrum sp. nov., apart from Merodon ottomanus Hurkmans. The genetic characterisation of species from the M. ottomanus group was performed through Maximum Parsimony (MP) and Maximum Likelihood (ML) analyses of the 5′ end of mitochondrial COI gene sequences, and the existence of the five above-mentioned independent taxa was supported. In addition, we confirmed the validity of M. auriolus sp. nov., M. paeninsula sp. nov., and M. ottomanus by using an integrative taxonomic approach including wing shape differences. Diagnoses, keys for both species groups, and the species they consist of, as well as distribution maps for all studied species, are provided.