Genetic structure of Ixodes scapularis (Ixodida: Ixodidae) and host association

In recent years, evidence for host-race formation in some hard tick species (Ixodida: Ixodidae) has accumulated. More specifically, genetic structure related to specific host association has been shown to occur in Ixodes uriae and Rhipicephalus (Boophilus) microplus. Ixodes scapularis, the vector of Lyme disease in the United States, exhibits higher levels of genetic diversity in the southern part of its distribution range than in the North. In order to verify whether or not genetic structure in I. scapularis may be linked to host association, I. scapularis immatures were collected from rodents and lizards on the same island along the Georgia coast during the same period. DNA was extracted from 50 ticks collected from rodents and 50 collected from lizards and 2 mitochondrial gene sequences (12SrDNA, control region) and one nuclear (ITS2) were sequenced from each specimen. The sequences were analyzed phylogenetically separately and as a concatenated matrix. Results indicate that there is no obvious relationship between I. scapularis phylogenetic clades and host groups, at least in the considered area. These findings, however, will need to be confirmed by analyzing larger samples from different geographical regions.