Genetic diversity and population structure of the Dermacentor nuttalli in Northern China inferred from microsatellite...

Dermacentor nuttalli is a dominant tick species in northern China and adjacent regions, where it poses significant threats to public health and the livestock industry through the transmission of diverse zoonotic pathogens. Understanding its population genetic structure is crucial for elucidating dispersal patterns and informing control strategies. However, the lack of high-resolution molecular markers has hindered such investigations. This study aimed to develop microsatellite markers and use them to assess the genetic diversity and structure of D. nuttalli populations across northern China.

Genome-wide microsatellite mining was conducted using the D. nuttalli reference genome. A total of 192 adult ticks were collected from five geographic locations in northern China. Genotyping was performed using 15 novel, highly polymorphic markers selected through a multi-step filtering process. Genetic diversity, population structure, molecular variance, gene flow and isolation by distance were investigated in population genetic analyses.

The 15 selected markers exhibited high polymorphism, with a mean polymorphic information content of 0.66. Genetic diversity varied among populations, with the Hulunbuir population showing the highest diversity levels. Population structure analyses consistently revealed two primary genetic clusters: one comprising populations from Yan'an, Bayannur, Ulanqab and Hulunbuir, and another consisting solely of the Hohhot population. Analysis of molecular variance indicated that 36.9% of the total genetic variation occurred among populations, reflecting substantial genetic differentiation (F_ST [fixation index] = 0.37). While gene flow was evident among some populations, it was limited between the two identified clusters. Notably, no significant isolation-by-distance pattern was detected (P > 0.05).

This study provides the first set of microsatellite markers for D. nuttalli and reveals a complex population structure in northern China. Host movement and anthropogenic factors appear to shape this structure more strongly than geographic distance. Notably, the isolated Hohhot population parasitizing wild hedgehogs suggests host-associated genetic differentiation and relatively localized transmission dynamics. These findings highlight the need for differentiated control strategies, including wildlife-focused surveillance in peri-urban areas and targeted livestock management in pastoral systems.