The characterisation and taxonomic utility of ITS2 in Tenthredopsis Costa, 1859 (Tenthredinidae: Hymenoptera) with some new records from Turkey

• The predicted secondary structure of ITS2 is characterised in Tenthredopsis.
• The predicted secondary structure of ITS2 is extremely branched in Tenthredopsis.
• The secondary structure of ITS2 are used as a molecular identifier in Tenthredopsis.

The taxonomic value of ITS2 has not been well established in insects and the data on its secondary structural properties is limited to a few studies. Here, we present the first data on the secondary structural properties of ITS2 in sawflies and test its utility as a molecular identifier in Tenthredopsis (Tenthredinidae: Symphyta). The ITS2 regions were sequenced from 67 specimens representing 14 species and six morphotypes of Tenthredopsis and their secondary structure were predicted and characterised. A sequence-structural alignment dataset of ITS2 was analysed by application of maximum likelihood method to see relationship among the specimens. Here, a relaxed approach has been adapted to identify and to elucidate species boundaries by considering the presence of CBCs, hemi-CBCs and unique length size of ITS2 in combination with morphology. The predicted secondary structure of ITS2 was extremely branched in contrast to common core structure found in many eukaryotes. A likely protein binding side was detected in Helix III and suggested to be a synapomorphy for Tenthredinidae. Eighteen species were identified under the relaxed approach applied here, of which Tenthredopsis lactiflua (Klug, 1817), Tenthredopsis ornata (Serville, 1823), Tenthredopsis stigma (Fabricius, 1798) and Tenthredopsis coquebertii (Klug, 1817) are new records for Turkey. The structural properties and length size of ITS2 prove useful in determination of species boundaries of closely related species. However, the full account on its taxonomic utility requires more empirical evidence in Hymenoptera.