Location, Location, Location: Geographic source of blacklegged tick (Ixodes scapularis) nymphs determines behavioral outcomes in laboratory studies

Ixodes scapularis is considered a significant medical and veterinary arthropod pest, capable of transmitting several pathogens that cause disease in humans and animals. Previous work has identified two distinct populations of I. scapularis in the United States (northern and southern), characterized by differences in their genetics and behavior. This study aimed to characterize and compare the lateral movement and feeding behaviors of nymphal I. scapularis between the northern and southern populations in the United States. Using laboratory-reared ticks from BEI (northern), Oklahoma State University (southern), and field-collected ticks from central Pennsylvania (Mid-Atlantic), behavioral bioassays were conducted to quantify distances traveled and velocities in a one-hour time frame. Ticks from the northern lineage walked longer distances and at faster speeds compared to ticks from the southern lineage. Field-collected ticks from central Pennsylvania, located between what is considered the northern and southern populations, exhibited similar movement behaviors as ticks from the southern population, even though ticks from the Mid-Atlantic are geographically categorized as the northern population. To compare feeding behaviors, colony-reared white-footed mice ( Peromyscus leucopus ) were artificially infested with northern and southern ticks, and the percentages of infestation and feeding successes were compared. Northern ticks had higher success in infestations and feeding to repletion compared to southern ticks. These behavioral differences in movement and feeding patterns provide additional evidence for the hypothesis that geographically distinct populations of I. scapularis exist across the United States. Researchers should consider these population differences when selecting tick lineages for behavioral studies and other blacklegged tick research.