Karyofund of holarctic midge Glyptotendipes barbipes (Staeger)

Set and frequencies of inversion banding sequences were recorded in the Palearctic and Nearctic natural populations of a Holarctic chironomid Glyptotendipes barbipes. This species has a hing level of inversion polymorphism in all populations studied (from 74 to 100 % of larvae were inversion heterozygotes in different populations). It is shown that the karyofund of G. barbipes includes inversion sequences found only in the Palearctic (Palearctic sequences, 43 %) or only in the Nearctic (Nearctic sequences, 34 %) and sequences common for both the Palearctic and Nearctic (Holarctic sequences, 23 %). Cytogenetic distances between populations (Dcg) were determined in the Palearctic (Dcg = 0.119 ± 0.011) and the Nearctic (Dcg = 0.022 ± 0.008). The greater cytogenetic differentiation among the Palearctic population is based on the presence in Yakutian populations, which formed a separate cluster on dendrogram (Fig. 6), of several holarctic sequences considered earlier as the Nearctic sequences only. The cytogenic distance become significantly greater between the Palearctic and Nearctic populations (Dcg = 0.520 ± 0.005). Cytogenetic distances between the Palearctic and Nearctic populations are based on the presence of endemic banding sequences, and mainly on inversion variants fixed as homozygotes.