Biology subjects

Gerbault-Seureau, M.

Publications and source records attributed to Gerbault-Seureau, M..

3 recordsLinked to original sources

bioRxiv2026

Karyotypic evolution in a diverse primate clade and the role of chromosomal fissions as barriers to gene flow

The classical model of chromosomal speciation is based on the observation that divergent species often differ in chromosome numbers and that heterokaryotypic hybrids show reduced fitness. Furthermore, positive correlations between the rates of karyotype evolution and speciation have been established in several groups of organisms. Yet, the mechanisms that make some lineages more prone to chromosomal fissions and fusions than others, and the causal role of such karyotype changes in speciation, are poorly understood. Here, we focus on the taxonomically and karyotypically diverse group of African monkeys, the guenons (tribe Cercopithecini), consisting of ~35 species with diploid chromosome numbers ranging from 48 to 72. We generated de novo genome assemblies for eight species with different karyotypes, and incorporated publicly available genomes from additionally three guenon species. Using the rhesus macaque as an outgroup, we identified 28 independent chromosomal fissions and 4 fusions in guenons. In line with previous cytogenetic studies, repeat composition around chromosomal breakpoints suggested that most fissions were non-centromeric, requiring the evolution of a new centromere in at least one of the fission products. In contrast to the expectation under strong underdominance, we found a paraphyletic distribution of several chromosomal fissions. Some of these phylogenetically discordant events could have resulted from interspecific hybridization, whereas others are more likely caused by incomplete lineage sorting, suggesting that fissioned and non-fissioned homologs segregated in ancestral guenon lineages for millions of years. Nevertheless, we find evidence for reduced introgression on rearranged chromosomes in an ancient cross-karyotypic gene flow event between Cercopithecus cephus and C. pogonias. Although this suggests that chromosomal fissions may have constituted barriers to gene flow in the guenon evolution, the signal was inconclusive or absent in two other investigated gene flow events. This study provides important first insights into the remarkable karyotypic diversification of guenons, and its role in generating reproductive barriers.

evolutionary biology↗

bioRxiv2026

Evolutionary history of alpha satellite DNA in Cercopithecini: comparative cytogenomics highlights the diversification pattern of primate centromere repeats

BackgroundAlpha satellites, a superfamily of AT-rich tandem repeats, are the primary DNA component of centromeres in Platyrrhini and Catarrhini. Analyses of the human genome suggest that centromeres behave like biological ridges, with new alpha satellite families expanding at the centromere core, splitting and displacing older ones towards the pericentromeres. The Cercopithecini tribe, which displays an unusual chromosomal evolution involving multiple chromosomal fissions and centromere formations, represents a promising model to enhance our understanding of alpha satellite DNA evolutionary history. We previously applied targeted sequencing to centromere DNA from two distant species drawn from the Cercopithecini terrestrial and arboreal lineages, and characterized six alpha satellite families exhibiting varying mean sequence identities. MethodsCombining classical and molecular cytogenetics, we mapped the chromosomal distribution of these alpha satellite families across 13 Cercopithecini, one Papionini, and one Colobinae species. A nuclear marker-based phylogeny provided an evolutionary framework for interpretation. ResultsOur phylogeny identifies the terrestrial and arboreal lineages, and a newly designated swamp clade. We observed significant interspecies variations in alpha satellite patterns, including differences in presence/absence and distinct chromosomal distribution patterns (centromeric, pericentromeric, or subtelomeric). Families previously described as heterogeneous (83-87% mean sequence identity) exhibit a centromeric position in the swamp lineage, which is characterized by conserved karyotypes. In contrast, these families show a pericentromeric distribution in the terrestrial and arboreal lineages, replaced at the centromere core by more homogeneous families (95-98% mean sequence identity). In the arboreal clade, which is characterized by highly fissioned karyotypes, putative evolutionary new centromeres show a unique co-occurrence of highly homogeneous and heterogeneous families. Conclusion & ImplicationsWe propose a comprehensive evolutionary scenario for alpha satellite DNA in Cercopithecini, where younger families arise at the centromere core, shift toward the pericentromeres as they age, and eventually face extinction. Our study suggests that alpha satellite DNA and chromosomes evolve in an interdependent manner, with satellite diversification and displacement occurring in parallel with chromosome fissions and centromere repositioning. This comparative cytogenomic approach provides both support for the human-based evolutionary model for alpha satellite DNA and novel temporal insights into its diversification dynamics. Beyond evolutionary genomics, our findings highlight the potential of alpha satellite DNA to complement systematic studies in deciphering complex primate evolutionary histories.

evolutionary biology↗

bioRxiv2022

Draft genome of the lowland anoa (Bubalus depressicornis) and comparison with buffalo genome assemblies (Bovidae, Bubalina)

Genomic data for wild species of the genus Bubalus (Asian buffaloes) are still lacking while several whole genomes are currently available for domestic water buffaloes. To address this, we sequenced the genome of a wild endangered dwarf buffalo, the lowland anoa (Bubalus depressicornis), produced a draft genome assembly, and made comparison to published buffalo genomes. The lowland anoa genome assembly was 2.56 Gbp long and contained 103,135 contigs, the longest contig being 337.39 kbp long. N50 and L50 values were 38.73 kbp and 19.83 kbp, respectively, mean coverage was 44x and GC content was 41.74%. Two strategies were adopted to evaluate genome completeness: (i) determination of genomic features with de novo and homology-based predictions using annotations of chromosome-level genome assembly of the river buffalo, and (ii) employment of benchmarking against universal single-copy orthologs (BUSCO). Homology-based predictions identified 94.51% complete and 3.65% partial genomic features. De novo gene predictions identified 32,393 genes, representing 97.14% of the references annotated genes, whilst BUSCO search against the mammalian orthologues database identified 71.1% complete, 11.7% fragmented and 17.2% missing orthologues, indicating a good level of completeness for downstream analyses. Repeat analyses indicated that the lowland anoa genome contains 42.12% of repetitive regions. The genome assembly of the lowland anoa is expected to contribute to comparative genome analyses among bovid species.

genomics↗