Phylogeographical structure of the tick Ixodes persulcatus: a novel view

The tick Ixodes persulcatus Schulze, 1930, has a wide distribution from the Baltic to the Far East and is a vector of a number of human pathogens. Thus, the study of the genetic structure and evolution of this species is of great epidemiological importance. rRNA genes were used as genetic markers to identify the phylogeographical structure of the ticks. The sequences of gene fragments of 28S (expansion segment D3) and mitochondrial 12S rRNA for 25 and 76 ticks, respectively, that had been collected in various regions of Russia in 2007-2011, were obtained. The sequences of the 28S rRNA D3 segment were identical for all ticks within the studied area. Analysis of the sequences of the mitochondrial 12S rRNA fragment revealed 4 haplotypes with one occurring at a frequency of 0.96. It is shown that the 'deep' population structure of I. persulcatus (McLain et al., 2001) was erroneous because of the inclusion of contaminating fungi sequences of 28S rRNA in the phylogenetic analysis. This was, possibly, due to the use of universal PCR primers that amplify the DNA of a wide range of eukaryotes, particularly of fungi which are common in samples of ticks. The influence of PCR conditions on the preferential amplification of the DNA of different organisms is also demonstrated.