COI mtDNA barcodes of freshwater leeches (Hirudinea) from Azerbaijan reveal lineage structure within taxa

Abstract

We present a COI-based assessment of freshwater leeches in Azerbaijan's Lankaran-Astara region. Between 2019 and 2021, we sampled 136 individuals from 33 wetlands across six districts and generated 15 new COI sequences, which were combined with curated GenBank records. Four species were confirmed in three families: Dina lineata (Erpobdellidae), Helobdella stagnalis (Glossiphoniidae), Hirudo orientalis (Hirudinidae), and Trocheta sp. (Erpobdellidae). Azerbaijani D. lineata populations occur as two distinct clades, one that includes an individual from Iraq (Lineage A) and one that includes an individual from Iran (Lineage B). These Asian lineages are separated from European D. lineata. An Azerbaijani Trocheta sp. specimen (FSM20) clusters with one from Iran on a distinct branch that is > 8% divergent from its closest congeners. We suggest this is likely a new species. Our results validate COI barcoding for resolving species boundaries in Caucasian leeches, and highlight the South Caucasus as a promising region for Trocheta diversity and discovery.