Spatial Heterogeneity of Tick-Borne Pathogens Outpaces Genetic Structuring in Anatolian Dermacentor reticulatus...

Understanding how vector population structure influences pathogen circulation remains a major challenge in tick-borne disease ecology, particularly in biogeographically transitional regions. Dermacentor reticulatus, a widespread Palearctic tick species and vector of multiple pathogens, provides a useful system to investigate this relationship in a biogeographically complex landscape. Here, we combined mitochondrial (cox1) and nuclear (ITS2) population genetic analyses with broad-spectrum pathogen screening in host-seeking D. reticulatus from Anatolia, a major ecogeographical transition zone of the eastern Palearctic. Population genetic analyses revealed moderate haplotype diversity, low nucleotide divergence, and limited regional structuring, with Anatolian populations clustering within widespread eastern Palearctic lineages. Global haplotype networks indicated extensive haplotype sharing with Eurasian populations, consistent with historical connectivity and possible host-mediated dispersal. In contrast to the relatively limited genetic structuring observed in tick populations, pathogen detections showed marked spatial heterogeneity. Rickettsia raoultii was detected predominantly in northeastern populations, whereas Coxiella burnetii detections were concentrated within a single locality. Other detected agents, including piroplasmids and Anaplasma phagocytophilum, occurred sporadically and showed no clear spatial pattern. Together, these findings suggest a mismatch between vector genetic structure and pathogen spatial distribution. Comparisons with sympatric Dermacentor marginatus populations further suggested species-specific differences in population structure and pathogen assemblages. The observed spatial heterogeneity in pathogen detections may reflect differences in local ecological conditions, host communities, and transmission dynamics. These findings provide new insight into the eco-epidemiological dynamics of D. reticulatus-associated pathogens in Anatolia and contribute to improved understanding of tick-borne pathogen (TBP) circulation at the southeastern margin of the Palearctic region.