Biology subjects

Darwin Tree of Life Consortium,

Publications and source records attributed to Darwin Tree of Life Consortium,.

4 recordsLinked to original sources

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↗

bioRxiv2026

340 dipteran genomes reveal the origin of Muller elements and sex chromosomes in Diptera

Diptera genome evolution is traditionally viewed through the lens of Drosophila melanogaster. To provide an unbiased picture of chromosome evolution in Diptera, we reconstructed six ancestral linkage groups (ALGs) and their rearrangements using 340 chromosome-level genome assemblies from 59 dipteran Families and two outgroups. Notably, Diptera ALGs are conserved in many Nematoceran lineages, while emergence of Brachycera coincided with four chromosomal fissions, which subsequently fused in various combinations. In Schizophora and relatives, a stable karyotype of five metacentric chromosomes and a chromosome homologous to the dot emerged that is remarkably stable with the notable exception of Drosophila, where the metacentric chromosomes became acrocentric Muller elements. Furthermore, our reconstruction reveals an ancient sex chromosome system associated with a small and gene-poor ALG that frequently fused to other chromosomes.

genomics↗

bioRxiv2026

Rapid chromosomal evolution and oligocentromeric drive in sedges and rushes

The chromosomes of most eukaryotes have a single centromere, a specialised region involved in chromosome partitioning to daughter cells. Inter-chromosomal rearrangement risks generating chromosomes with two centromeres or none, disrupting segregation. Holocentric chromosomes, with centromere function distributed along the chromosome, are hypothesised to better tolerate inter-chromosomal rearrangement. However, evidence linking centromere organisation to rearrangement rate has been lacking. Sedges and rushes (Cyperaceae and Juncaceae) are specifically polycentric: they have several satellite-based centromeres per chromosome, whereas centromere location in "asatellitic" holocentrics is solely defined epigenetically. Using 36 chromosome-level genomes, we quantify extraordinary rearrangement rates and annotate candidate polycentromeres. Under our polycentromeric drive model, we expected satellite sequence, polycentromere architecture, and karyotype to evolve to exploit biased segregation during asymmetric meiosis. We find satellite turnover but also deep sequence conservation. Polycentromeric organisation seems constrained by chromosome size, and rearrangements are more stable when chromosomes have fewer polycentromeres, despite breakpoint regions being enriched for polycentromeres. Notably, we find putative monocentromeres in Carex myosuroides, which would be the first evidence for reversion to monocentricity in eukaryotes, and no identifiable polycentromeres in Cyperus rotundus, possibly a transition to asatellitic holocentricity. Overall, we demonstrate that this clade is powerful for linking centromere organisation to genome evolution.

genomics↗

bioRxiv2022

MitoHiFi: a python pipeline for mitochondrial genome assembly from PacBio High Fidelity reads

BackgroundPacBio high fidelity (HiFi) sequencing reads are both long (15-20 kb) and highly accurate (>Q20). Because of these properties, they have revolutionised genome assembly leading to more accurate and contiguous genomes. In eukaryotes the mitochondrial genome is sequenced alongside the nuclear genome often at very high coverage. A dedicated tool for mitochondrial genome assembly using HiFi reads is still missing. ResultsMitoHiFi was developed within the Darwin Tree of Life Project to assemble mitochondrial genomes from the HiFi reads generated for target species. The input for MitoHiFi is either the raw reads or the assembled contigs, and the tool outputs a mitochondrial genome sequence fasta file along with annotation of protein and RNA genes. Variants arising from heteroplasmy are assembled independently, and nuclear insertions of mitochondrial sequences are identified and not used in organellar genome assembly. MitoHiFi has been used to assemble 374 mitochondrial genomes (369 from 12 phyla and 39 orders of Metazoa and from 6 species of Fungi) for the Darwin Tree of Life Project, the Vertebrate Genomes Project and the Aquatic Symbiosis Genome Project. Inspection of 60 mitochondrial genomes assembled with MitoHiFi for species that already have reference sequences in public databases showed the widespread presence of previously unreported repeats. ConclusionsMitoHiFi is able to assemble mitochondrial genomes from a wide phylogenetic range of taxa from Pacbio HiFi data. MitoHiFi is written in python and is freely available on github (https://github.com/marcelauliano/MitoHiFi). MitoHiFi is available with its dependencies as a singularity image on github (ghcr.io/marcelauliano/mitohifi:master).

bioinformatics↗