Biology subjects

De-Kayne, R.

Publications and source records attributed to De-Kayne, R..

6 recordsLinked to original sources

bioRxiv2024

Extensive haplotype diversity in a butterfly colour pattern supergene is fuelled by incomplete recombination suppression

Supergenes can evolve when recombination-suppressing mechanisms like inversions promote co-inheritance of alleles at two or more polymorphic loci that affect a complex trait. Theory shows that such genetic architectures can be favoured under balancing selection or local adaptation in the face of gene flow, but they can also bring costs associated with reduced opportunities for recombination. These costs may in turn be offset by rare gene flux between inverted and ancestral haplotypes, with a range of possible outcomes. We aimed to shed light on these processes by investigating the BC supergene, a large genomic region comprising multiple rearrangements associated with three distinct wing color morphs in Danaus chrysippus, a butterfly known as the African monarch, African queen and plain tiger. Using whole-genome resequencing data from 174 individuals, we first confirm the effects of BC on wing color pattern: background melanism is associated with SNPs in the promoter region of yellow, within an inverted subregion of the supergene, while forewing tip pattern is most likely associated with copy number variation in a separate subregion of the supergene. We then show that haplotype diversity within the supergene is surprisingly extensive: there are at least six divergent haplotype groups that experience suppressed recombination with respect to each other. Despite high divergence between these haplotype groups, we identify an unexpectedly large number of natural recombinant haplotypes. Several of the inferred crossovers occurred between adjacent inversion modules, while others occurred within inversions. Furthermore, we show that new haplotype groups have arisen through recombination between two pre-existing ones. Specifically, an allele for dark coloration in the promoter of yellow has recombined into distinct haplotype backgrounds on at least two separate occasions. Overall, our findings paint a picture of dynamic evolution of supergene haplotypes, fuelled by incomplete recombination suppression.

evolutionary biology↗

bioRxiv2022

Hybridization and a mixture of small and large-effect loci facilitate adaptive radiation

Adaptive radiations represent some of the most remarkable explosions of diversification across the tree of life. However, the constraints to rapid diversification and how they are sometimes overcome, particularly the relative roles of genetic architecture and hybridization, remain unclear. Here, we address these questions in the Alpine whitefish radiation, using a whole-genome dataset that includes multiple individuals of each of the 22 species belonging to six ecologically distinct ecomorph classes across several lake-systems. We reveal that repeated ecological and morphological diversification along a common environmental axis is associated with both genome-wide allele frequency shifts and a specific, larger effect, locus, associated with the gene edar. Additionally, we highlight the role of introgression between species from different lake-systems in facilitating the evolution and persistence of species with unique phenotypic combinations and ecology. These results highlight the role of both genome architecture and secondary contact with hybridization in fuelling adaptive radiation.

evolutionary biology↗

bioRxiv2021

Stepwise evolution of a butterfly supergene via duplication and inversion

Supergenes maintain adaptive clusters of alleles in the face of genetic mixing. Although usually attributed to inversions, supergenes can be complex, and reconstructing the precise processes that led to recombination suppression and their timing is challenging. We investigated the origin of the BC supergene, which controls variation in warning colouration in the African Monarch butterfly, Danaus chrysippus. By generating chromosome-scale assemblies for all three alleles, we identified multiple structural differences. Most strikingly, we find that a region of >1 million bp underwent several segmental duplications at least 7.5 million years ago. The resulting duplicated fragments appear to have triggered four inversions in surrounding parts of the chromosome, resulting in stepwise growth of the region of suppressed recombination. Phylogenies for the inversions are incongruent with the species tree, and suggest that structural polymorphisms have persisted for at least 4.1 million years. In addition to the role of duplications in triggering inversions, our results suggest a previously undescribed mechanism of recombination suppression through independent losses of divergent duplicated tracts. Overall, our findings add support for a stepwise model of supergene evolution involving a variety of structural changes.

evolutionary biology↗

bioRxiv2021

Genome assembly of Danaus chrysippus and comparison with the Monarch Danaus plexippus

Milkweed butterflies in the genus Danaus are studied in a diverse range of research fields including the neurobiology of migration, biochemistry of plant detoxification, host-parasite interactions, evolution of sex chromosomes, and speciation. We have assembled a nearly chromosomal genome for Danaus chrysippus (known as the African Monarch, African Queen, and Plain Tiger) using long read sequencing data. This species is of particular interest for the study of genome structural change and its consequences for evolution. Comparison with the genome of the North American Monarch Danaus plexippus reveals generally strong synteny, but highlights three inversion differences. The three chromosomes involved were previously found to carry peaks of intra-specific differentiation in D. chrysippus in Africa, suggesting that these inversions may be polymorphic and associated with local adaptation. The D. chrysippus genome is over 40% larger than that of D. plexippus, and nearly all of the additional [~]100 Megabases of DNA comprises repeats. Future comparative genomic studies within this genus will shed light on the evolution of genome architecture.

genomics↗

bioRxiv2019

A de novo chromosome-level genome assembly of Coregonus sp. \"Balchen\": one representative of the Swiss Alpine whitefish radiation

BackgroundSalmonids are of particular interest to evolutionary biologists due to their incredible diversity of life-history strategies and the speed at which many salmonid species have diversified. In Switzerland alone, over 30 species of Alpine whitefish from the subfamily Coregoninae have evolved since the last glacial maximum, with species exhibiting a diverse range of morphological and behavioural phenotypes. This, combined with the whole genome duplication which occurred in the ancestor of all salmonids, makes the Alpine whitefish radiation a particularly interesting system in which to study the genetic basis of adaptation and speciation and the impacts of ploidy changes and subsequent rediploidization on genome evolution. Although well curated genome assemblies exist for many species within the Salmonidae family, genomic resources for the subfamily Coregoninae are lacking.\n\nFindingsPacBio sequencing from one wild caught Coregonus sp. \"Balchen\" from Lake Thun was carried out to [~]90x coverage. PacBio reads were assembled independently using three different assemblers, Falcon, Canu and wtdbg2 and subsequently scaffolded with additional Hi-C data. All three assemblies are of high quality based on standard metrics, and when comparing the assemblies to a previously published linkage map and when mapping additional short-read data ([~]30x Illumina data) to it.\n\nConclusionsHere, we present the first de novo genome assembly for the Salmonid subfamily Coregoninae. Our final wtdbg2 reference sequence was assembled into 40 chromosome-scale scaffolds with a total length of 2.2Gb, an N50 of 51.9Mb and was 93.3% complete for BUSCOs. It comprised of [~]52% TEs and contained 46,397 genes.

genomics↗

bioRxiv2018

A European whitefish linkage map and its implications for understanding genome-wide synteny between salmonids following whole genome duplication

Genomic datasets continue to increase in size and ease of production for a wider selection of species including non-model organisms. For many of these species highly contiguous and well-annotated genomes are unavailable due to their prohibitive complexity and cost. As a result, a common starting point for genomic work in non-model species is the production of a linkage map, which involves the grouping and relative ordering of genetic markers along the genome. Dense linkage maps facilitate the analysis of genomic data in a variety of ways, from broad scale observations regarding genome structure e.g. chromosome number and type or sex-related structural differences, to fine scale patterns e.g. recombination rate variation and co-localisation of differentiated regions. Here we present both a sex-averaged and sex-specific linkage maps for Coregonus sp. \"Albock\" containing 5395 single nucleotide polymorphism (SNP) loci across 40 linkage groups to facilitate future investigation into the genomic basis of whitefish adaptation and speciation. The map was produced using restriction-site associated digestion (RAD) sequencing data from two wild-caught parents and 156 F1 offspring in Lep-MAP3. We discuss the differences between our sex-avagerated and sex-specific maps and identify synteny between C. sp. \"Albock\" linkage groups and the Atlantic salmon (Salmo salar) genome. Our synteny analysis confirms that many patterns of homology observed between Atlantic salmon and Oncorhynchus and Salvelinus species are also shared by members of the Coregoninae subfamily.

evolutionary biology↗