Comparison of the DNA sequences and secondary structure of the mitochondrial 16S rRNA gene of Ixodes kingi, Ixodes sculptus and Ixodes angustus

The DNA sequences and predicted secondary structure of domains IV and V of the mitochondrial (mt) 16S rRNA gene were compared for three species of Ixodes: Ixodes kingi, Ixodes sculptus and Ixodes angustus. Each species had a unique set of DNA sequences for the 16S gene. Many of the differences in DNA sequence within and among species occurred in a “hypervariable” region of domain V, and either represented partial or full compensatory base pair changes that maintained the helices within the secondary structure, or nucleotide alterations at unpaired positions that had no effect on the secondary structure. The results of the phylogenetic analyses revealed that I. kingi, I. sculptus and I. angustus were placed in a clade with some other species of the subgenera Pholeoixodes and Ixodiopsis. In addition, individuals of I. sculptus from Saskatchewan (Canada) and Colorado (USA) did not form a monophyletic clade, suggesting the possible existence of cryptic species.