Biology subjects

Van Belleghem, S.

Publications and source records attributed to Van Belleghem, S..

4 recordsLinked to original sources

bioRxiv2025

Polygenic basis of incipient reproductive isolation in hybridizing populations is revealed by pangenomic and epigenetic divergence

Incipient reproductive isolation in the presence of gene flow has traditionally been attributed to a small number of major-effect loci under strong selection, representing only a minor fraction of the genome. Using the Heliconius erato adaptive radiation--a butterfly species with populations at varying levels of genetic differentiation--we employed a pan-genome approach to investigate genome-wide mutational divergence, epigenetic changes, and structural variation contributing to divergence. In contrast to earlier studies that identified only a few highly divergent loci, our high-resolution analysis reveals widespread divergence across the genome, suggesting polygenic barriers to gene flow. Epigenetic divergence assessed using ATAC-seq, highlights population-specific differences in chromatin accessibility, which may reflect SNPs distribution or precede genetic differentiation by reshaping regulatory landscapes. We also identified new structural variants, including polymorphic indels in open chromatin, that further associate with genomic divergence. Together, these findings show that the genomic landscape of H. erato is shaped by a dynamic interplay of mutational changes, epigenetic modifications, and structural variation. We emphasize the role of developmental, behavioral, and ecological adaptations and provide a broader perspective on the functional genetic basis of genome-wide divergence in Heliconius. This emerging polygenic framework offers a more detailed understanding of how reproductive barriers evolve under ongoing gene flow.

evolutionary biology↗

bioRxiv2024

A single giant cell at the origin of an evolutionary innovation

Key innovations play a central role in the diversification of lineages, yet our understanding of the mechanisms underlying their emergence remains fragmented. The propelling fan is a key innovation associated with the diversification of Rhagovelia water striders into fast flowing streams. Here, we show that a single giant cell is responsible for the development of the fan throughout embryogenesis. RNA interference against the fan-specific gene family gsha/mogsha depleted the fan in the embryo but did not alter the giant cell, indicating that these genes are not required for specifying the identity of this cell. gsha/mogsha instead seem to activate the expression of cuticular genes during early development, suggesting a role of these genes in regulating the accumulation of fan structural proteins. We also show that Hox genes act to block the giant cell in the fore- and rear-legs, thus restricting its fate to the mid-legs - the pair of legs that generates movement on water. In addition, Hox expression is specifically excluded from the giant cell, thus allowing the expression of the fans developmental genetic program. This study reveals that a single cell can be sufficient to generate innovative traits that have been central for a lineage to acquire new ecological opportunities and burst into diversification. One-sentence summaryA single giant cell orchestrates the developmental genetic program of a key innovation

evolutionary biology↗

bioRxiv2018

Genomic architecture and introgression shape a butterfly radiation

We here pioneer a low-cost assembly strategy for 20 Heliconiini genomes to characterize the evolutionary history of the rapidly radiating genus Heliconius. A bifurcating tree provides a poor fit to the data, and we therefore explore a reticulate phylogeny for Heliconius. We probe the genomic architecture of gene flow, and develop a new method to distinguish incomplete lineage sorting from introgression. We find that most loci with non-canonical histories arose through introgression, and are strongly underrepresented in regions of low recombination and high gene density. This is expected if introgressed alleles are more likely to be purged in such regions due to tighter linkage with incompatibility loci. Finally, we identify a hitherto unrecognized inversion, and show it is a convergent structural rearrangement that captures a known color pattern switch locus within the genus. Our multi-genome assembly approach enables an improved understanding of adaptive radiation.

evolutionary biology↗

bioRxiv2018

Evolution at two time frames: polymorphisms from an ancient singular divergence event fuel contemporary parallel evolution

When species occur in repeated ecologically distinct habitats across their range, adaptation may proceed surprisingly fast and result in parallel evolution. There is increasing evidence that such cases of rapid parallel evolution are fueled by standing genetic variation, but the origin of this genetic variation remains poorly understood. In Pogonus chalceus beetles, short- and long-winged ecotypes have diverged in response to contrasting hydrological regimes and can be repeatedly found along the Atlantic European coast. By analyzing genomic variation across the beetles distribution, we reveal that genomically widespread short-wing selected alleles evolved during a singular divergence event, estimated at ~0.19 Mya. The ancient and differentially selected alleles are currently polymorphic in all populations across the range, allowing for the fast evolution of one ecotype from a small number of random individuals, as low as 5 to 15, of the populations of the other ecotype. Our results suggest that cases of fast parallel ecological divergence might be the result of evolution at two different time frames: divergence in the past, followed by repeated selection on the divergently evolved alleles after admixture. We suggest that this mechanism may be common and potentially further driven by periods of geographic isolation imposed by large-scale environmental changes such as glacial cycles.

evolutionary biology↗