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

Abstract

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.

Keywords

• Chrysolina
• COI
• DNA barcoding
• ITS2

Türkiye'de dağılış gösteren Chrysolina Motschulsky, 1860 (Coleoptera: Chrysomelidae) cinsine dahil türlerin moleküler tanımlamasında COI ve ITS2 belirteçlerinin karşılaştırmalı analizleri

Öz

Bu çalışma, böceklerde tür sınırlarını belirlemede iki moleküler belirtecin—sitokrom c oksidaz alt birimi I (COI) geni ve iç transkribe edilmiş aralık II (ITS2) bölgesinin—etkinliğini araştırmıştır. COI geni, böcek taksonomisinde tür sınırlarını belirlemede yaygın olarak kullanılmasına rağmen, ITS2 bölgesi bu amaçla daha az test edilmiştir. Türkiye genelinden toplanan Chrysolina cinsine (Coleoptera: Chrysomelidae) dahil 25 birey analiz edilmiştir. Moleküler analizler 2017 yılında Ege Üniversitesi Fen Fakültesi Zooloji Bölümü Moleküler Sistematik Laboratuvarı’nda gerçekleştirilmiş, veri analizleri ise 2025 yılında tamamlanmıştır. Her bir belirteç ve birleşik veri seti temelinde filogenetik ağaçların topolojisi ve türlerin monofiletikliği Bayesian yaklaşımıyla değerlendirilmiştir. Bu çalışma, Türkiye’de Chrysolina türleri için COI ve ITS2 belirteçlerinin ilk karşılaştırmalı analizini sunmaktadır. Elde edilen sonuçlar, her iki belirtecin de morfolojik ayrımları moleküler düzeyde desteklediğini ortaya koymuştur. COI, ITS2 ve birleşik veri setleriyle oluşturulan filogenetik ağaçlarda tüm türler monofiletik gruplar oluşturmuştur. Bulgular, ITS2 bölgesinin genetik çeşitliliğin değerlendirilmesi ve tür tanımlanmasında COI kadar etkili olabileceğini göstermektedir. Bu çalışma, ITS2’nin böcek taksonomisinde güvenilir bir moleküler belirteç olarak potansiyelini vurgulamakta ve Chrysolina cinsi içindeki tür sınırlarının anlaşılmasına katkı sağlamaktadır.

Anahtar Kelimeler

• Chrysolina
• COI
• DNA barkodlama
• ITS2

Kaynakça

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