Biology subjects

Buggs, R.

Publications and source records attributed to Buggs, R..

11 recordsLinked to original sources

bioRxiv2026

Genomic signals of local adaptation in UK black alder populations (Alnus glutinosa)

Black alder (Alnus glutinosa) is a native tree species in the British Isles, which it colonised after the last glaciation from continental refugia. It is now a widespread pioneer species, thriving on wetlands and riverbanks. We present whole genome sequence data for 324 alder seedlings grown from seed collected from 44 populations across the UK. Among these we found two triploids and one sample with trisomy at chromosome five. Removing these, we found little population genetic structure apart from diverging northern populations with lower diversity. Using Latent-Factor Mixed Models (LFMM) analyses we identified 1,364 loci whose allele frequencies were significantly associated with environmental variables. Of these loci, 93% were associated with the number of snow days. In contrast, the greatest total genomic signal (variance in SNP effect sizes of 7.38 million SNP loci) was observed for mean temperature of the wettest quarter and annual number of frost days. Estimates of maladaptation using 1.49 million SNPs, predicted that northern populations are worst adapted to present and future worst-case climates. Our results suggest that similarity of source-site temperature variables should be prioritised when choosing seed sources for new planting, and northern populations could benefit from assisted gene flow from the south.

plant biology↗

bioRxiv2026

Mapping the distribution of elms in Britain after a century of Dutch elm disease

The establishment of novel pests and pathogens that devastate populations of trees is increasing around the world, giving rise to policy and management decisions about how to restore treescapes. Such decisions may be informed by the example of Dutch elm disease (DED) which caused most mature elms in Europe and North America to be lost in the mid-20th Century. Although affected elms can regenerate, they succumb again after several years. Considerable effort has been made to restore elm through: (1) cloning and breeding of surviving local trees, (2) introduction of resistant Asiatic species, (3) introduction or production of hybrids bred from local and Asiatic species. As trees are planted out into the landscape, it is necessary to record them, and monitor their survival. Here, we compile and map 82,244 elm trees in Britain recorded as 269 distinct elm species, hybrids and cultivars. The vast majority of records are for surviving field elm, English elm and wych elm, which would grow again to maturity if the virulence of the pathogen could be attenuated. The most commonly planted elms were the hybrids: Nanguen (commercial name Lutece), followed by New Horizon, Ademuz, Lobel and Sapporo Autumn Gold, each of which had over 200 occurrences. The current elm-scape of Britain represents much restoration effort and contains considerable genetic diversity.

plant biology↗

bioRxiv2026

Genetic mapping of Dutch elm disease resistance

Dutch elm disease (DED) has killed millions of field elms (Ulmus minor) in Britain and Europe since the 1970s, causing incalculable damage to landscapes and their associated biodiversity. While the species U. minor is highly susceptible to DED, some east Asian and Himalayan species of elm are resistant. These Asiatic species differ in their growth and form to U. minor and cannot fully substitute for it in the landscape. Several breeding programmes have attempted to generate trees that combine DED-resistance with the growth and form of U. minor via hybridisation and back-crossing. These have been partly successful, but further breeding is needed to fully realise these ambitions. Most recently in Britain, a complex resistant hybrid Wingham (FL493) was crossed with a surviving U. minor tree in Tonge Mill, Kent. Sixty progeny from this cross were tested for field resistance to DED and show segregation for this trait. Here, we analyse the genome of these progeny in order to: (1) construct a linkage map of the elm genome, and (2) identify regions of their genome derived from east Asian and Himalayan species that could be associated with DED-resistance. Such knowledge could accelerate future breeding programmes and enhance our understanding of the mechanistic basis of resistance.

genomics↗

bioRxiv2025

Genetic basis of traits and local adaptation in UK silver birch

Knowledge of the genomic basis of phenotypes in forest trees lags that of other economically important organisms. We sequenced the genomes of 2054 silver birch trees from 20-year-old field trials at three locations in Britain. Each trial site contains trees from the same 29 source populations, and one trial site (Drummond) is outside the climate envelope of the source sites. We discovered many single nucleotide polymorphisms (SNP), and a structural polymorphism, associated with several growth traits. Using models trained with genome-wide SNPs we estimate the genomic breeding values of 148 plus trees. We discover 117 SNPs significantly associated with source-site environmental variables, but genetic offset estimates using these SNPs provide poor predictions of tree growth rates (Drummond excluded). They are outperformed in this task by offset estimates using thousands of non-significant SNPs. Such estimates for Drummond in current climates are higher than for source sites under a future worst case climate scenario.

genomics↗

bioRxiv2025

Recurrent evolution of cryptic triploids in cultivated enset increases yield

The high incidence of polyploidy in crops could be explained if domestication involved the selection of polyploids (cytotypes with more than two sets of chromosomes). Ancestral horticulture could have targeted desirable traits including yield, robustness to stress and to disease, rather than requiring knowledge of polyploidy itself. We find evidence for this process underway in enset (Ensete ventricosum, Musaceae) - a highly resilient crop constituting the main staple for over 20 million people in Ethiopia, which is clonally propagated and cultivated for its starch-rich corm and pseudostem. Prior to this study, enset was thought to be exclusively diploid (2n = 2x = 18). Using a newly-assembled chromosome-scale reference genome, and sequence data from 723 wild and domesticated enset individuals from southwestern Ethiopia, we demonstrate that around 20% of cultivated enset clones are triploid. We show that triploidy has arisen multiple times independently, that the triploid lineages have been given distinct landrace names, and planted disproportionately frequently. As well as providing evidence for enduring selection on triploids, our results reveal valuable genetic diversity captured by these triploid lines. They represent key resources for scientifically directed breeding of this major crop in the Ethiopian agrosystem, and could improve food security in sub-saharan Africa. Author SummaryDuplication of a species entire genome (polyploidization) plays an important part in evolution. Domestication may have favoured polyploid crops including wheat, coffee, potato, cotton, strawberry, and banana. It has been proposed that this trend is explained by the selection of advantageous traits exhibited by polyploids compared to their relatives with unduplicated genomes. These desirable traits include bigger fruits, seeds or other edible organs, and better tolerance to stress and disease. We unexpectedly find that a large proportion of cultivated enset lines have three copies of their genome (triploidy) instead of two (diploid). Enset is a highly resilient crop in the banana family; its stem and leaves are processed to provide one of the main food sources for over 20 million people in Ethiopia. Prior to our study, enset was thought to be exclusively diploid. Farmers use landrace names that distinguish diploids from triploids without having this new genetic information, showing the differences between them are recognised and given importance. Triploids were planted disproportionately and appear to grow faster, suggesting they are being selected for their higher productivity. These triploid ensets are an important genetic resource for scientifically directed breeding of new varieties, which could improve food security in sub-saharan Africa.

evolutionary biology↗

bioRxiv2024

Genetic barcodes for ash (Fraxinus) species and generation of new wide hybrids

Native ash tree species in Europe and North America are being devastated by ash dieback and the emerald ash borer, respectively. As worldwide ash species differ in their level of susceptibility to these threats, hybrid breeding may allow resistance to be transferred among species. However, we do not know the extent to which distantly related ash species can be crossed, and many ash species are difficult to identify from morphology alone leading to some mislabelling in living collections. Here, we develop a genetic barcode system for the identification of Fraxinus species based on three low-copy-number protein coding genes. We also conduct experimental crosses among ash species in different sections. Our barcodes are effective in identifying ash samples to sectional level and in some cases to species level, and can also identify hybrids. They highlight that F. mandshurica, F. platypoda and F. chiisanensis may be frequently mistaken for one another in living collections. We succeeded in generating ten wide hybrid plants: two of section Melioides (species: F. pennsylvanica) {square} section Fraxinus (species: F. excelsior) and eight of section Ornus (species unclear) {square} section Fraxinus (species: F. excelsior). One hybrid from each of our crosses has survived natural infection with the ash dieback pathogen in Ireland. We also discovered a hybrid between section Melioides (species: F. latifolia) {square} section Fraxinus (species: F. excelsior) formed spontaneously in the ash collection at Kew. Our findings facilitate the deployment of global ash species diversity in response to alien pests and pathogens. Societal impact statementThe world-wide diversity of ash trees includes genetic information encoding resistance to the ash dieback fungus and the emerald ash borer beetle, which are currently devastating ash populations in Europe and North America. In order to mobilise this genetic diversity in conventional breeding programmes we need to be able to accurately identify ash species from around the world, and cross them with one another. Here, we present a genetic barcoding system for ash species, and a series of hybridisation experiments between European ash and other species. Two of the hybrids show early promise against ash dieback.

plant biology↗

bioRxiv2022

A first draft genome of Holm oak (Quercus ilex L.), the most representative species of the Mediterranean forest and the Spanish agrosilvopastoral ecosystem dehesa

The holm oak (Quercus ilex L.) is the most representative species of the Mediterranean Basin and the agrosilvopastoral Spanish "dehesa" ecosystem. Being part of our life, culture, and subsistence since ancient times, it has great environmental and economic importance. More recently, there has been a renewed interest in using the Q. ilex acorn as a functional food due to its nutritional and nutraceutical properties. However, the holm oak and its related ecosystems are threatened by different factors, with oak decline syndrome and climate change being the most worrying on the short and medium term. Breeding programs informed by selection of elite genotypes seems to be the only plausible biotechnological solution to rescue populations under threat. To achieve this and other downstream analyses, we need a high-quality Q. ilex reference genome. Here, we introduce the first draft genome assembly of Q. ilex using long-read sequencing (PacBio). The assembled nuclear haploid genome has 530 contigs totaling 842.2 Mbp (N50 = 3.3 Mbp), of which 448.7 Mb (53%) are repetitive sequences. We annotated 39,443 protein-coding genes and Benchmarking Universal Single-Copy Orthologs analysis detected 412 out of 425 expected complete and single-copy genes (94.80%) within the Q. ilex genome. The chloroplast genome size was 142.3 Kbp with 149 protein-coding genes successfully annotated. This first draft should allow for the validation of - omics data as well as the identification and functional annotation of genes related to phenotypes of interest such as those associated to resilience against oak decline syndrome and climate change, higher acorn productivity and nutraceutical value.

genomics↗

bioRxiv2022

Genomic evidence of natural selection for ash dieback resistance

Rapid evolution via small shifts in allele frequencies at thousands of loci are a long- standing neo-Darwinian prediction but are hard to characterize in the wild. European ash tree (Fraxinus excelsior) populations have recently come under strong selection by the invasive fungal pathogen Hymenoscyphus fraxineus. Using genomic prediction models based on field trial phenotypes and 7,985 loci, we show a shift in genomically estimated breeding values in an ancient woodland, between adult trees established before the epidemic started and juvenile trees established since. Using simulations, we estimate that natural selection has eliminated 31% of the juvenile population. Thus, we document a highly polygenic heritable micro-evolutionary adaptive change over a single generation in the wild. One-Sentence SummarySubtle changes at thousands of genomic locations in one generation allow woodland trees to respond to a new selective pressure

evolutionary biology↗

bioRxiv2021

Extraction and high-throughput sequencing of oak heartwood DNA: assessing the feasibility of genome-wide DNA methylation profiling

Tree ring features are affected by environmental factors and therefore are the basis for dendrochronological studies to reconstruct past environmental conditions. Oak wood often provides the data for these studies because of the durability of oak heartwood and hence the availability of samples spanning long time periods of the distant past. Wood formation is regulated in part by epigenetic mechanisms such as DNA methylation. Studies of the methylation state of DNA preserved in oak heartwood thus could identify epigenetic tree ring features informing on past environmental conditions. In this study, we aimed to establish protocols for the extraction of DNA, the high-throughput sequencing of whole-genome DNA libraries (WGS) and the profiling of DNA methylation by whole-genome bisulfite sequencing (WGBS) for oak (Quercus spp.) heartwood drill cores taken from the trunks of living standing trees spanning the AD 1776-2014 time period. Heartwood contains little DNA, and large amounts of phenolic compounds known to hinder the preparation of high-throughput sequencing libraries. Whole-genome and DNA methylome library preparation and sequencing consistently failed for oak heartwood samples more than 100 and 50 years of age, respectively. DNA fragmentation increased with sample age and was exacerbated by the additional bisulfite treatment step during methylome library preparation. Relative coverage of the non-repetitive portion of the oak genome was sparse. These results suggest that quantitative methylome studies of oak hardwood will likely be limited to relatively recent samples and will require a high sequencing depth to achieve sufficient genome coverage.

plant biology↗

bioRxiv2020

Resolving phylogeny and polyploid parentage using genus-wide genome-wide sequence data from birch trees

Numerous plant genera have a history including frequent hybridisation and polyploidisation, which often means that their phylogenies are not yet fully resolved. The genus Betula, which contains many ecologically important allopolyploid tree species, is a case in point. We generated genome-wide sequence data for 27 diploid and 31 polyploid Betula species or subspecies using restriction site associated DNA (RAD) sequences assembled into contigs with a mean length of 675 bp. We reconstructed the evolutionary relationships among diploid Betula species using both supermatrix and species tree methods. We identified progenitors of the polyploids according to the relative rates at which their reads mapped to contigs from different diploid species. We sorted the polyploid reads into different putative sub-genomes and used the extracted contigs, along with the diploid sequences, to build new phylogenies that included the polyploid sub-genomes. This approach yielded a highly evidenced phylogenetic hypothesis for the genus Betula, including the complex reticulate origins of the majority of its polyploid taxa. The genus was split into two well supported clades, which differ in their seed-wing morphology. We propose a new taxonomy for Betula, splitting it into two subgenera. We have resolved the parentage of many widespread and economically important polyploid tree species, opening the way for their population genomic study.

evolutionary biology↗

bioRxiv2020

Bidirectional introgression between Betula tianshanica and Betula microphylla and its implications for conservation

O_LIMolecular markers can allow us to differentiate species that occupy a morphological continuum, and detect patterns of allele sharing that can help us understand the dynamics of geographic zones where they meet. Betula microphylla is a declining wetland species in NW China that forms a continuum of leaf morphology with its relative Betula tianshanica. C_LIO_LIWe use ecological niche models (ENM) to predict the distribution of B. microphylla, B. tianshanica and the more commonly occurring B. platyphylla. We use restriction-site associated DNA sequencing and SSRs to resolve their genetic structure and patterns of allele sharing. C_LIO_LIENM predicted an expansion of suitable range of B. tianshanica into B. microphylla since the Last Glacial Maximum and the contraction of B. microphyllas range in the future. We resolved the species identification of some intermediate morphotypes. We found signatures of bidirectional introgression between B. microphylla and B. tianshanica with SNPs showing more admixture than SSRs. Introgression from B. microphylla into B. tianshanica was greater in the Tianshan Mountains where the two species have occurred in proximity. Unexpectedly, introgression from B. tianshanica into B. microphylla was widespread in the Altay Mountains where there are no records of B. tianshanica occurrence. C_LIO_LIThis presence of B. tianshanica-derived alleles far beyond the species current range could be due to unexpectedly high pollen flow, undiscovered populations of B. tianshanica in the region, incomplete lineage sorting, or selection for adaptive introgression in B. microphylla. These different interpretations have contrasting implications for the conservation of B. microphylla. C_LI

evolutionary biology↗