Comparative analyses of COI and ITS2 in the molecular identification of Chrysolina Motschulsky, 1860 (Coleoptera: Chrysomelidae) in Türkiye

This study investigated the effectiveness of two molecular markers—the cytochrome c oxidase subunit I (COI) gene and the internal transcribed spacer II (ITS2) region—in delineating species boundaries in insects. While COI is widely used in insect taxonomy to define species boundaries, ITS2 has been less frequently tested. A total of 25 individuals from the genus Chrysolina (Coleoptera: Chrysomelidae), distributed across Türkiye, were analysed. Molecular analyses were conducted in 2017 at the Molecular Systematics Laboratory of the Department of Zoology, Faculty of Science, Ege University, and data analyses were completed in 2025. Using a Bayesian approach, they examined phylogenetic tree topology and species monophyly based on each marker and combined datasets. This marks the first comparative study of COI and ITS2 within Chrysolina species in Türkiye. Results showed that both markers supported morphological distinctions at the molecular level. All species formed monophyletic groups in trees constructed from COI, ITS2, and combined datasets. These findings suggest that the ITS2 may be as effective as the COI in evaluating genetic diversity and identifying species. The study highlights the potential of ITS2 as a reliable molecular marker in insect taxonomy and enhances understanding of species boundaries within the genus Chrysolina.