Defining the eastern range limit of the semiterrestrial leech Haemopis elegans (Hirudinea: Haemopidae) in Ukraine: Morphology, phylogeny, and range modeling

The semiterrestrial leech Haemopis elegans Moquin-Tandon, 1846 is widely distributed across Europe, though its eastern range limit remains poorly defined. This study examines the hypothesis that environmental conditions east of the Lviv region in Ukraine are unsuitable for the establishment of H. elegans, resulting in its observed range limit. Specimens of H. elegans were collected from Pohulianka Park in Lviv, western Ukraine, and their morphological characteristics were examined. In addition, a specimen from Argentré, France, was included in the study. Molecular phylogenetic analysis was performed using mitochondrial DNA markers (cytochrome c oxidase subunit I) to confirm species identity, assess genetic diversity, and reveal phylogenetic relationships within the species. To predict the species’ potential distribution under current environmental conditions, species distribution modeling was applied using occurrence records and key environmental variables. Morphological analysis confirmed the distinguishing features of H. elegans, such as body coloration and reproductive system traits, in comparison to the related and sympatric H. sanguisuga (Linnaeus, 1758). Our findings reveal distinct genetic differences among populations within the species’ range, including the identification of new haplotypes in Ukraine and France. Both morphological and molecular data support the co-occurrence of these two Haemopis species in Ukraine. Species distribution modeling indicates low habitat suitability for H. elegans east of its known range, while field surveys and genetic data confirm its absence or discontinuity in those areas.