Zilov, D. | bioRxiv Science

bioRxiv2026

338 coleopteran genomes reveal exceptional rearrangement variation compared to other insect orders

Chromosomal rearrangements reshape genome architecture, but rate variation across the tree of life remains poorly understood. Analysing 338 beetle (Coleoptera) genomes, we inferred eight ancestral linkage groups. No species retained these linkage groups, whereas the most frequent karyotypes of 10 or 11 chromosomes evolved at least 65 times through independent rearrangements. Rearrangement rates vary widely across lineages, with exceptionally high rates associated with major species radiations. Comparisons to 340 fly and 210 butterfly and moth genomes reveal the highest rates of long-term persistent rearrangements in beetles and that the beetle X chromosome traces back to the ancestor of Holometabola. We identified frequent X chromosome changes, mostly representing recent autosomal-X fusions, but no fissions. For autosomes, key rearrangement predictors include chromosome size, repeats and centromere position.

evolutionary biology↗

bioRxiv2025

Genome structure and molecular phylogeny of the only Eurasian Boechera species, Boechera falcata (Brassicaceae)

Boechera falcata (Turcz.) Al-Shehbaz (earlier known as Arabis turczaninowii Ledeb.) is a herbaceous perennial belonging to the East Siberian, boreal-steppe ecotype. It is the only species of the diverse genus Boechera that grows on the Eurasian continent, all others being endemic to North America and Greenland. In all likelihood, Boechera falcata or its ancestral lineage migrated from North America to Eastern Siberia across the Bering Land Bridge when it was exposed during the height of Pleistocene glaciation. Boechera is interesting in that many species in this genus are allodiploid and triploid apomicts that arose through complex hybridization of sexual species and ecotypes. To date, the genomes of only two American Boechera species, B. stricta and B. retrofracta, have been sequenced, analyzed, and published. In the present study, we sequenced, assembled to the chromosome level, and analyzed the B. falcata genome, which was highly homozygous with a size of 189.36 Mb. Molecular phylogenetic analysis of the nuclear and organelle genomes revealed a high degree of relatedness of B. falcata to North American relatives. Investigation of the structure of pachytene, mitotic, and diakinesis chromosome spreads (n = 14) using cytogenetic analysis and comparative chromosome painting (CCP) allowed us to identify all 22 genomic blocks of crucifers and found that five of the seven B. falcata chromosomes were collinear with their corresponding chromosomes in the ancestral Boechereae genome, and two chromosomes had undergone pericentric and paracentric inversions. Allelic analysis of the apomixis marker APOLLO gene revealed that B. falcata contains only sex alleles of this gene. The availability of the genome of the only Asian Boechera species will facilitate studies of the evolution and phylogeny of Brassicaceae species and apomixis.

genomics↗