Cytogenetic differentiation of natural populations of Chironomus obtusidens (Diptera, Chironomidae)

The cytogenetic structure of Siberian and European populations of Chironomus obtusidens Goetgh. was studied. The clear differentiation of these populations was revealed using quantitative analysis of sets and frequencies of inversion banding sequences. The Siberian populations were found to have six new inversion sequences, and the alternative obtG2 sequence dominated instead of the main obtG1 sequence typical of European populations. In general, chromosomal polymorphism was 3--4 times higher in the Siberian populations. Therefore, the cytogenetic distances (Dcg) between the Siberian and European populations were higher (Dcg 0.059--0.097) than Dcg between the populations in each of the geographic zones investigated (Dcg 0--0.015). The NJ phylogenetic tree constructed for the chromosomal evolution of the genus Chironomus demonstrates that Chironomus obtusidens is the most divergent member among Palaearctic species of the obtusidens group. In addition, it is closer related to the Nearctic Ch. decorus group.