Chromosomal polymorphism has been investigated in 7 natural populations from West Europe, West Siberia and Sakha Republic (Yakutia). The pool of polytene chromosome banding sequences of this species includes 15 banding sequences. The chromosomal polymorphism has been revealed in 5 of chromosomal arms. The most polymorphic is the arm B, there are 4 banding sequences in it. There are 3 banding sequences in the arm A. The arms D, E and G have 2 banding sequences. No chromosome rearrangements have been found in the arms C and F. The populations of Chironomus cingulatus differ clearly in the number and frequencies of banding sequences. This is evidence of that different gene sequences are adaptive in different populations.
Using RAPD markers, polymorphism and differentiation of genomic DNA was examined in seven natural populations of Chironomus plumosus from Europe, Siberia, and North America. All these populations showed high polymorphism of genomic DNA. The Palearctic and Nearctic populations of this species were not statistically significantly different in the genomic DNA polymorphism level. The genetic distance (GD), which characterizes the extent of intraspecific differentiation of population genetic structure, was determined among the natural populations of C. plumosus. The genetic distance was on average 0.0245. It was demonstrated that genetic structures of the Palearctic and Nearctic populations of C. plumosus was differentiated to a higher extent than in Palearctic. However, the genetic distances between the populations from different zoogeographical zones (0.313) did not exceed the level characteristic of the among-population differences, which do not disturb the species genetic integrity.
The karyotype structure and chromosomal polymorphisms were investigated in 6 natural and 2 laboratory populations of Chironomus nuditarsis from Europe and Asia. The pool of rearranged polytene chromosome banding sequences of this species was determined that includes 16 inversion banding sequences and sequences with giant DNA-knobs (ndtG1k, ndtG2k). Obvious differences were demonstrated in the level of chromosomal polymorphism between European and Asian (Siberian) populations: the former were highly polymorphic, while the latter were practically monomorphic. It was suggested to consider the Siberian populations as marginal one. Cytogenetic distances between populations of C. nuditarsis as well between C. nuditarsis and the related species C. plumosus were estimated. The data obtained show that chromosomal rearrangements play a very important role in cytogenetic divergence of populations.
The karyotypes and chromosomal polymorphism of Chironomus pseudothummi were investigated in different parts of its range. It was established that chromosomal variability in the natural populations of this species was represented mainly by the inversion polymorphism of arm G. Only rare and unique inversions were found as heterozygous in arms C, D, and E. In total, the 14 banding sequences of polytene chromosomes form the banding sequences pool of Ch. pseudothummi. Geographic differences in distribution of chromosomal banding sequences throughout the range were established. The presence of banding sequences pstG1 and pstG2 is characteristic of European populations. Banding sequence pstG1 was completely vanished with simultaneous increase in frequency of pstG2 and appearance of new inversion banding sequence pstG3 in Siberian populations. The differences in the set of the rare and unique inversions in arms C, D, and E between west-European and west-Siberian populations were revealed.