Sequence variation of ribosomal internal transcribed spacers (ITS) in commercially important phytoseiidae mites

Preliminary work is needed to assess the usefulness of different markers at different taxonomic scales when a new group is analyzed, such as the comme rcially important Phytoseiidae mites. We investigate here the level of sequ ence variation of the nuclear ribosomal spacers ITS 1 and 2 and the 5.8S ge ne in six species of Phytoseiidae: Neoseiulus californicus, N. fallacis, Eu seius concordis, Metaseiulus occidentalis, Typhlodromus pyri and Phytoseiul us persimilis. As expected, the 5.8S gene (148 base pairs) is markedly cons erved and displays little variation in between genera comparisons. ITS1 and ITS2 show contrasting patterns: while the ITS2 is short (80-89 bp) and sho ws little variation, the ITS1 is longer (303-404 bp) and is very variable i n sequence. This fact compromises reliable nucleotide homologies when compa ring the genera. The comparison of ITS1 sequence similarity at the species level might be useful for species identification, however, the value of ITS in taxonomic studies does not extend to the level of the family. The intra specific variations of ITS were investigated in three species: N. californi cus, N. fallacis and E. concordis. The first species has identical ITS1 seq uences and the last two display low polymorphism (2 nucleotide substitution s). The ITS2 and 5.8S sequences were identical in all three subspecies comp arisons.