[Molecular criteria in insects systematics: bar-coding gene COI range of variability as a taxonomic criterion for genus, tribe, and subfamily, with Chironominae and Orthocladiinae midges (Chironomidae, Diptera) as a case study].

Contemporary systematics of insects is based mainly on morphological traits. However, their usage is limited both by high variability and complications in comparisons of remote taxa due to low number of common traits. In whole, this leads to a somewhat subjective view when elaborating the system. Unlike morphological ones, molecular traits of taxa, revealed by use of marker genes such as gene cytochrome-c-oxidase I (COI), are less variable and more uniform, which allows them to be used as a criterion of genus, tribe, and subfamily for a wide range of organisms. Application of molecular criteria appears to be all the more important when constructing the system for groups of organisms with high morphological and specific diversity, such as midges (Chironomidae, Diptera). Last years, the DNA-sequence of gene COI is becoming widely used for species identification as a bar-coding one. Its use as a criterion for taxa of super-species level is hampered by its high nucleotide variability. We established the bounds of COI nucleotide and aminoacid divergence between midge species of Chironominae subfamily belonging to the same genus, same tribe, different tribes, as well as between species of Chironominae and Orthocladiinae subfamilies. It is shown that the level of aminoacid divergence reflects molecular boundaries of genus and tribe better than nucleotide one. It can be stated that if the level of aminoacid divergence falls within the limits from 0 to 1.7% then a pair of species compared belongs to the same genus; if it falls within the limits from 1.7 to 4.0% then they belong to the same tribe; within the limits from 4.6 to 6.3%--to different tribes; if it exceeds 7.9%--to different subfamilies. The accuracy of identification when using these ranges turns out to be not less than 75%. In this regard, bounds of COI sequence aminoacid divergence may be used as taxonomic criteria for midge genus, tribe or subfamily.

[Molecular phylogeny and the time of divergence of minges (Chironomidae, Nematocera, Diptera) inferred from a partial nucleotide sequence of the cytochrome oxidase I gene (COI)].

This is the first study to infer the phylogenetic structure of minges of the subfamily Chironominae from the amino acid sequence of cytochrome oxidase I (COI). The subdivision of Chironominae into two tribes, Chironomini and Tanytarsini, has been confirmed. The segregation of the genera Pseudochironomus and Riethia into a separate tribe has not been confirmed. Stenochironomus gibbus forms a branch considerably deviating from the subfamily Chironominae. The genus Micropsectra is formed by a large polyphyletic cluster that also includes the genera Virgotanytharsus, Reotanytharsus, Kenopsectra, and Parapsectra. Tanytarsus is the basal genus of the tribe Tanytarsini. The times of divergence of the main taxa of Chironominae have been estimated. The calculated time of divergence of the genus Chironomus disproves the assumption that it is phylogenetically old.

[Comparison of Chironomus usenicus and Chironomus curabilis with species of the group plumosus (Diptera) inferred from the mitochondrial DNA gene COI and by the polytene chromosomes banding pattern].

The sequence of a 595-bp fragment of the mitochondrial COI gene was determined for the species Chironomus usenicus and Chironomus curabilis of the genus Chironomus. Phylogenetic reconstructions based on the analysis of the COI gene sequence coincide on the whole with cytogenetic data, permitting Ch. usenicus and Ch. curabilis to be regarded as members of the group plumosus. Chironomus usenicus and Ch. plumosus have identical COI gene sequences. Two hypotheses explaining this identity are considered: inheritance of mtDNA from one of the parental species during hybridogenesis and horizontal transfer of mitochondrial genes.