Sequence comparisons of the internal transcribed spacer region of ribosomal genes support close relationships between parasitic ants and their respective host species (Hymenoptera:Formicidae)

A fragment of the internal transcribed spacer (ITS-I) adjacent to the 5.8S rRNA gene of 20 myrmicine ant species was sequenced. Sequence comparisons were carried out between 11 species of the tribe Leptothoracini, five species of the tribe Tetramoriini, three species of the tribe Solenopsidini and one species of the tribe Myrmicini. Additionally, the formicine ant Camponotus ligniperda (tribe Camponotini) was analyzed as an outgroup species. Among all investigated species, the fragment had a variable length of approximate to 230-380 bp with only a few conserved sequence elements. The sequences of this fragment were perfectly identical within four palearctic populations of Leptothorax acervorum indicating that intraspecific variation is rather low. Within the species of Tetramoriini (including Anergates atratulus) 94.1% of sequence positions were identical, 95.6% within the species of the Leptothorax s.str.-group and 64.6% within the species of the Myrafant-group. Phylogenetic analysis reveals that the social parasites Harpagoxenus sublaevis, Doronomyrmex goesswaldi, D. kutteri and D. pacis, Chalepoxenus muellerianus as well as Strongylognathus alpinus and Teleutomyrmex schneideri are most closely related to the groups of their respective host species, which generally confirms the taxonomical classifications of the subfamily Myrmicinae based on morphological criteria. The taxonomical positions of the species A. atratulus has as yet been uncertain, however, sequence comparison of the ITS-1 fragment leads to the conclusion that A, atratulus rather belongs to the tribe Tetramoriini than to the Solenopsidini.