On species boundaries in chigger mites: an integrative approach to Hirsutiella spp. (Trombiculidae) in Poland.

The morphological identification of chiggers has traditionally been the primary method used in taxonomic research on these mites. However, this approach is often inadequate and can lead to incorrect conclusions. The difficulties in identifying these mites primarily arise from the limited resolution of morphological traits used for diagnosis at both the genus and species levels. As a result, there is an increasing need to rely on additional criteria, particularly molecular analyses, to confirm the status of various genera and species. This study aimed to clarify the taxonomic status of species within Hirsutiella, particularly focusing on Hirsutiella willmanni, which has been considered a synonym of H. zachvatkini by some researchers. The larvae were collected from Clethrionomys glareolus, at various locations across Poland, following previous literature reports of the presence of both Hirsutiella species in the country. Based on an integrative approach that includes morphological as well as molecular data, specifically from the mitochondrial cytochrome c oxidase subunit I (COI) and large ribosomal subunit (28S rRNA) markers, we confirm the separate species identity of H. zachvatkini and H. willmanni. The results confirm the higher effectiveness of the 28S gene in distinguishing between chigger species. The larvae of H. willmanni are redescribed, accompanied by a revised diagnosis of larvae of H. zachvatkini. Genetic differentiation between populations of H. zachvatkini from the Carpathians, Sudetes, and the lowland and upland areas north of the mountain ranges has been revealed.