Inversion polymorphism of the non-biting midge Camptochironomus pallidivittatus Edwards, 1929 (Diptera, Chironomidae) from populations of the Lower Volga region and Central Caucasus

The karyotype of Camptochironomus pallidivittatus Edwards, 1929 (Diptera, Chironomidae) from six populations of the Lower Volga region and Central Caucasus (the northern macroslope) has been studied. In populations of C. pallidivittatus from the Central Caucasus, 11 banding sequences (BS) were found; one sequence, pal B10, was new for the species. In the Saratov population, 11 BS were also found, three of which were new for the species-pal A3, pal B11, and pal B12. The banding sequences detected for the first time have not yet been found in other parts of the area of this species and may be endemic to these regions. In the studied populations of C. pallidivittatus, banding sequences were found that were non standard, but fixed in the karyotype. This is indicative of some degree of chromosomal divergence. These banding sequences include pal A2.2 in arm A and pal B10.10 in arm B in the Central Caucasus region, as well as pal B2.2 and pal G2.2 in the Lower Volga region. Arms A, B, D, and G in the Central Caucasian populations and A, B, and D in the Saratov oblast were polymorphic. The composition of heterozygous sequences between populations from different regions coincided only in arm D (pal D1.2). In arms A and B, the set of heterozygous BS was different: pal A1.2 and pal B1.10 sequences were found in the Central Caucasian populations, and pal A1.3 and B11.12 were found in Saratov oblast. The number of genotypic combinations of C. pallidivittatus was higher in the Central Caucasus region, whereas the number of zygotic combinations was higher in the Saratov population. The percentage of heterozygous larvae in the Central Caucasian populations varied from 20 to 80, whereas all individuals in the Saratov population had heterozygous inversions. Zygotic combinations of larvae in all the studied populations were different.