Biology subjects

Lukhtanov, V. A.

Publications and source records attributed to Lukhtanov, V. A..

3 recordsLinked to original sources

bioRxiv2022

Chromosomal conservatism vs chromosomal megaevolution: enigma of karyotypic evolution in Lepidoptera

In the evolution of many organisms, periods of very slow genome reorganization (=chromosomal conservatism) are interrupted by bursts of numerous chromosomal changes (=chromosomal megaevolution). However, the patterns, mechanisms, and consequences of conservative and rapid chromosomal evolution are still poorly understood and widely discussed. Here we show that in blue butterflies (Lepidoptera: Lycaenidae), the periods of chromosome number conservatism are characterized by the real stability of most autosomes and the highly dynamic evolution of the sex chromosome Z, which, due to autosome-sex chromosome fusions and fissions, is carried out according to the cycle Z=>NeoZ1=>Z=>NeoZ2=>Z=>NeoZ3. These fusions and fissions result in a fluctuation of chromosomal number ({+/-}1) around the ancestral value, a phenomenon previously observed (but not explained) in numerous groups of Lepidoptera. In the phase of chromosomal megaevolution, the explosive increase in the chromosome number occurs mainly due to simple chromosomal fissions, in some cases complicated by autosomal translocations. Interestingly, these translocations are not random and found to occur only between fragmented chromosomes originated from the same primary linkage group. We also found that the Z chromosomes of two closely related Lysandra species are differentiated by a large inversion. We argue that the special role of sex chromosomes in speciation can be reinforced via sex chromosome - autosome fusion. The cycles of fusions and fissions of sex chromosomes with autosomes, such as those found in the blue butterflies, indicate that the species divergence driven by neo-Z chromosome formation is widely distributed in Lepidoptera.

evolutionary biology↗

bioRxiv2022

Diversity and evolution of telomere and subtelomere DNA sequences in insects

In insects, two types of telomere length maintenance are known: telomerase-dependent, resulting in chromosome ends consisting of short nucleotide repeats (typically TTAGG), and telomerase-independent, resulting in chromosome ends consisting of long nucleotide repeats or transposon-like elements. However, only a few species have been previously studied with regard to their telomere DNA sequences. Here, based on analysis of chromosome-level genome assemblies, I present the data on telomere and subtelomere organization for 180 species from 148 genera, 53 families and 8 orders of insects. Analysis of these taxa reveals that in fact chromosome ends of most insect species have an intermediate structure and consist of numerous arrays of short telomeric repeats interspersed with telomere-specific non-LTR retrotransposons. An unexpectedly high level of diversity of short telomeric motifs (22 variants ranging in length from 1 to 17 nucleotides) is documented. Telomeres consisting of long repeats (from 173 to 374 bp) are confirmed for flies (the order Diptera) and also found in the orders Odonata and Hymenoptera. The most unusual telomere structure is found in the bee Lasioglossum lativentre, in which the chromosomes possess the short telomeric repeat TTAGGTCTGGG at only one end, whereas opposing ends terminate with medium and long repeats. I conclude that different types of telomere organization and numerous variants of long and short T-containing motifs, including the (T)n mononucleotide sequence, are compatible with the performance of telomere functions. I argue that both telomerase-dependent and telomerase-independent mechanisms for maintaining telomere length operate simultaneously in many insects. The balance between them and the exchange of sequences between telomeres and subtelomeres are most likely the key factors that determine the structure and evolution of telomeres. SignificanceMultilayer telomeres, resulted from numerous, site-specific insertions of retrotransposons into the region of short telomeric repeats, are not an aberrant type of organization, as previously thought. They are widely distributed among insects and can represent up to 30-40 % of eukaryotic species diversity. Accordingly, the telomere maintenance mechanism based on the joint work of telomerase-dependent and telomerase-independent mechanisms can also be extremely widespread in nature.

evolutionary biology↗

bioRxiv2020

Phylogenetic position and taxonomic rearrangement of Davidina (Lepidoptera, Nymphalidae), an enigmatic butterfly genus new for Europe and America

Davidina, an enigmatic butterfly genus described from China in the 19th century, has been long time considered a member of the family Pieridae due to its pierid-like wing pattern. In the 20th century, it was transferred to the family Satyridae (now subfamily Satyrinae of Nymphalidae) based on analysis of genitalia structure and placed next to the species-rich genus Oeneis (subtribe Satyrina), being separated from the latter by supposed differences in wing venation. Here we conducted phylogenetic and taxonomic study of the subtribe Satyrina using analysis of molecular and morphological characters. We show that the genus Oeneis is not monophyletic, and consists of two non-sister, genetically diverged and morphologically differentiated groups (Oeneis s.s. and Protoeneis). We also demonstrate that Davidina is closely related to Protoeneis, not to Oeneis s.s. To avoid the discovered non-monophyly and morphological heterogeneity, several species should be extracted from Oeneis and transferred to the genus Davidina. As a consequence, we conclude that the name Protoeneis Gorbunov, 2001 is congeneric with Davidina Oberthur, 1879. We also conclude that Davidina is not a monotypic Chinese endemic genus as it has been previously supposed, but is composed of nine species and has a broad distribution area in the Holarctic region including Europe and America.

zoology↗