Background

In the ribosomal genome, the first and second internal transcribed spacers (ITS1 and ITS2) are located between the genes coding for 18S, 5.8S and 28S in the ribosomal DNA cluster. Although spacer sequences are not present in the mature ribosomal RNA molecules, they mediate the cleavage of the great RNA precursor [1] and form stable secondary structures [2]. There is evidence that the deletion of ITS2 affects the maturation of both the small and large subunit rRNA [3]. Whilst many muta-tions become fixed in a population through natural se-lection and genetic drift, the non-coding spacer regions in ITS2 evolve through a pattern of concerted evolution [4]. Typically, ITS2 exhibits a low level of sequence vari-ation within species and a high level of divergence be- * Correspondence: htownson@liverpool.ac.uk1Department of Vector Biology, Liverpool School of Tropical Medicine,Claudia Caterina Paredes-Esquivel1,2 and Harold Townson1