To investigate the genetic specificity of Ixodes granulatus ticks collected from 
Taiwan, the genetic identities and phylogenetic relationships were analyzed by 
comparing the sequences of the internal transcribed spacer 2 (ITS2) region 
obtained from 27 strains of ticks representing twelve species of Ixodes. Five 
major clades can be easily distinguished by neighbour-joining analysis and were 
congruent by maximum-parsimony method. All these I. granulatus ticks collected 
from Taiwan and Japan were genetically affiliated to a monophyletic group with 
highly homogeneous sequences (95.8-99.5% similarity), and can be discriminated 
from other species and subgenera of Ixodes ticks with a sequence divergence 
ranging from 13.6% to 62.9%. Moreover, interspecific analysis revealed that four 
distinct lineages are evident between Ixodes ticks, and all these I. granulatus 
ticks collected from Taiwan and Japan belong to the same lineage. Our results 
provide the first investigation on the genetic specificity of I. granulatus 
ticks, and demonstrate that all these I. granulatus ticks represent a unique 
lineage distinct from other species and subgenera of Ixodes ticks. The 
feasibility of ITS2-based genetic analysis for species-specific identification 
of I. granulatus ticks around East Asia was highly anticipated.