The first record of Chironomusnuditarsis Keyl, 1961 from Sevan Lake (Armenia) confirmed by morphology, karyotype and COI gene sequence

Chironomusnuditarsis Keyl, 1961 is recorded from Sevan Lake for the first time. This species is widespread in Europe, the Caucasus, and Siberia. For species identification, we used a comprehensive approach that included morphological, cytogenetic and molecular genetic analyses. Morphological analysis showed a high similarity with the description. Nine chromosome banding sequences ndtA1, ndtA2, ndtB2, ndtC1, ndtD1, ndtE1, ndtF1, ndtG1, and ndtG2 were found. The banding sequences ndtA1, ndtA2, ndtG1, and ndtG2 are species-specific for C.nuditarsis and allow us to accurately distinguish it from the sibling species Ch.curabilis Belyanina, Sigareva et Loginova, 1990. Molecular-genetic analysis of the COI gene sequences has shown low genetic distances of 0.38-0.95% in the sibling species Ch.nuditarsis and Ch.curabilis complex and the insufficiency of using a single COI as a molecular marker for their separation.

Karyotype characteristics and gene COI sequences of Chironomusbonus Shilova et Dzhvarsheishvili, 1974 (Diptera, Chironomidae) from the South Caucasus (Republic of Georgia, Paravani river)

The study presents data on the karyotype characteristics and the mitochondrial gene COI sequences of the non-biting midge Chironomus bonus Shilova et sDzhvarsheishvili 1974 (DipteraChironomidae) from the South Caucasus. The species belongs to the Ch. plumosus group of sibling species one of the most widespread and successful groups in the genus Chironomus Meigen 1803. The karyotype of the studied population is monomorphic. The morphological and chromosomal characteristics of Ch. bonus from the Caucasus are similar to those previously described for this species (Kiknadze et al. 1991a). In the phylogenetic tree based on the COI gene sequences one can observe several clear clusters. We named them Palearctic Ch. plumosus Far Eastern Ch. borokensis-Ch. suwai and Nearctic Ch. entis-Ch. plumosus clusters. The calculated K2P genetic distances within each cluster have not exceeded the 3% threshold for the genus Chironomus. Contrary to this the distances between the clusters exceed this range and correspond to separate species. The Ch. bonus sequences belong to the cluster consisting of Ch. plumosus (Linnaeus 1758) sequences from European populations and do not form a separate clade of the phylogenetic tree. One can suppose that the origin of the Ch. plumosus group of sibling species dates back to 5.75–3.43 million years ago (Mya) the epochs of Late Miocene (7,3–5,3 Mya) and early Pliocene (5,3–2,58 Mya). On the other hand Palearctic Ch. plumosus Far Eastern Ch. borokensis-Ch. suwai and Nearctic Ch. entis-Ch. plumosus clusters appeared relatively recently in the Middle Pleistocene 1.288–0.307 Mya. The possible relationship between the climate changes in the Pliocene and the origin of the Ch. plumosus group are discussed. Chironomidae

Karyotype and COI gene sequence of Chironomusheteropilicornis Wülker, 1996 (Diptera, Chironomidae) from the Gydan Peninsula, Russia

The karyotype features and gene COI sequence of Chironomusheteropilicornis Wülker, 1996 from the Gydan Peninsula are presented for the first time. Nine banding sequences were determined, eight of them hpiA2, hpiB1, hpiC1, hpiC2, hpiD1, hpiE1, hpiF3 and hpiG1 were previously known from European, Georgian (South Caucasus) and Siberian populations. One new banding sequence for Ch.heteropilicornis, hpiB2, was found. The hpiA2 banding sequence was found in all individuals, and this is its second finding after the Georgian population (Karmokov 2019). The hpiF3 banding sequence was found only in the homozygous state. Additional B-chromosomes are absent. The genetic distances (K2P) between Ch.heteropilicornis COI gene sequence from Gydan Peninsula and Norway are 1.1--1.3%, and Georgia - 1.8%, much lower than the commonly accepted threshold of 3% for species of genus Chironomus Meigen, 1803. The phylogenetic tree for COI gene sequences estimated by Bayesian inference showed geographically determined clusters of Norway and Gydan and a separate lineage of the Georgian population of Ch.heteropilicornis. The analysis of karyotype and COI gene sequences shows that the population of Ch.heteropilicornis from the Gydan Peninsula has an intermediate position within the Ch.pilicornis group between Georgian, Yakutian and Norwegian populations. The position of Ch.pilicornis Fabricius, 1787 from Canada and Greenland on the phylogenetic tree is discussed.

Karyotype and COI sequences of Chironomus sokolovae Istomina, Kiknadze et Siirin, 1999 (Diptera,Chironomidae) from the bay of Orkhon River, Mongolia

Chironomus sokolovae Istomina, Kiknadze et Siirin, 1999 (Diptera, Chironomidae) is recorded from Mongolia for the first time. Eleven banding sequences determined in the Mongolian population were previously known from Altai and Yenisei populations: sokA1, sokB1, sokB2, sokC1, sokC2, sokD1, sokD2, sokE1, sokF1, sokF2 and sokG1. The additional B-chromosomes are absent. DNA-barcoding of COI gene was carried out for this species for the first time. The phylogenetic tree estimated by Bayesian inference showed a high similarity of the studied species with Ch. acutiventris Wülker, Ryser et Scholl, 1983 from the Chironomus obtusidens-group. The estimated genetic distance K2P between Ch. sokolovae and Ch. acutiventris is much lower (0.38%) than the commonly accepted threshold of 3% for species of genus Chironomus Meigen, 1803. Our results show that the accepted cytogenetic criteria of species level in the genus Chironomus are more in accordance with morphological ones of the same level, than with molecular-genetic criteria accepted for species COI genetic distance.

Karyotype characteristics, chromosomal polymorphism and gene COI sequences of Chironomus heteropilicornis Wülker, 1996 (Diptera, Chironomidae) from the South Caucasus

The study presents data on the karyotype characteristics, features of chromosomal polymorphism and the gene COI sequences of Chironomus heteropilicornis Wülker, 1996 (Diptera, Chironomidae) from the South Caucasus. We found 8 banding sequences in the Caucasian population. Overall, The Caucasian population of the species can be characterized as having a low level of polymorphism. We found one new banding sequence hpiA2 in the banding sequence pool of Ch. heteropilicornis. We observed inversion polymorphism only in the arm F. The dendrogram of genetic distances by Nei criteria (1972) shows a clear separation of the Caucasian population from populations of Siberia. At the same time, the distance between populations of Siberia and the population of South Caucasus (0.379-0.445) almost reach the mean distance (0.474 ± 0.314) between subspecies (Gunderina 2001). Due to this, we can assume that the population of South Caucasus separated from Siberian populations at the level of subspecies. Constructed on data for COI gene sequences the phylogenetic tree estimated by the Bayesian inference shows that the sequences of Ch. heteropilicornis from the South Caucasus form a separate line in the general branch of Ch. heteropilicornis sequences. At the same time, calculated K2P genetic distances between Ch. heteropilicornis sequences from Norway and Caucasus (2.0-2.2%) do not exceed the 3% threshold for the genus Chironomus.