Biology subjects

Borrell, J. S.

Publications and source records attributed to Borrell, J. S..

14 recordsLinked to original sources

bioRxiv2026

Humans could become the greatest driver of biosphere net gain in Earth history, but we are currently the second fastest driver of biosphere loss

Human activity is transforming the shape, size, and resilience of Earths biosphere, degrading and augmenting Holocene baseline conditions at various scales, and replacing the wild biosphere with an anthropogenically modified one. We evaluate episodes of biosphere change throughout Earth history and compare them with contemporary and near-future anthropogenic changes, developing the concept of biosphere disruptors - agents that force global-scale macroevolutionary change. Transient disruptors are short-lived agents (mean 8.0x105 years), including massive volcanism and asteroid impacts. Persistent disruptors, including atmospheric and ocean oxygenation and land plant evolution, remain in the Earth System over long timescales (mean 1.6x108 years). In the geological record, transient disruptors are associated with temporary but sometimes massive biosphere degradation, whereas persistent disruptors are associated with sustained biosphere enhancement. Most anthropogenic biosphere impacts resemble those of past transient disruptors, globally degrading wild biomass and biodiversity. Humanity is driving the second highest rate of biosphere degradation in Earth history after the Cretaceous-Palaeogene bolide impact. However, humanity is the first disrupting agent capable of reflecting on and potentially transforming its impact on planetary habitability. If we can achieve this, humanity could drive the greatest rate of increase in planetary habitability in Earth history on centennial to millennial timescales.

paleontology↗

bioRxiv2025

Distance to future climate analogues reveals refugia for agricultural adaptation

Future climate trends are predicted to cause a dramatic shift in the geographic distribution of global agriculture. Mapping the distance to future analogues provides a crucial measure of adaptation potential, and reveals steep slope agriculture, regions with small field sizes, and ancient centres of crop domestication have more proximal climate analogues. Drawing parallels from wild biodiversity conservation, these landscapes could play a critical role as climate refugia for agrobiodiversity.

ecology↗

bioRxiv2025

Differing drivers of range-wide genetic diversity across previously glaciated Northern hemisphere landscapes

O_LIThe latitudinal gradient (LG) hypothesis predicts a poleward decrease of genetic diversity. Similarly, the central-marginal hypothesis (CMH) predicts higher genetic diversity in range centres than margins. We examined these patterns in Europe (EU), North America (NA) and East Asia (EA), which experienced contrasting patterns of landscape fragmentation. C_LIO_LIWe compiled genetic variation data for 445 plant species and 8,530 populations. We calculated ecological metrics comprising distance to the range margin and native climatic niche margin, distance to refugia, latitude and altitude. We applied Bayesian inference to evaluate the relationships between genetic variation and ecological metrics. C_LIO_LIWe found universal support for the CMH, with populations at the centres of species ranges and/or native climatic niches exhibiting higher genetic diversity than those at the margins and stronger patterns in woody versus herbaceous plants. Evidence for a LG in diversity was less consistent with latitude: negatively correlated with genetic diversity in EU, positively correlated in EA, and no correlation in NA. C_LIO_LIOur analysis supports the view that the LG is largely driven by latitudinal trends in glaciation, particularly in EU, but highlights that glaciation patterns and their resulting impacts on landscape genetic diversity were more heterogeneous in NA and EA. C_LI

evolutionary biology↗

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↗

bioRxiv2022

Introduced crops supplement rather than replace indigenous crops in an African center of agrobiodiversity

O_LICrop diversity plays a major role in underpinning food security. It is especially important to smallholder and subsistence farmers, who often rely on crop diversity for stable and resilient production. Despite this, global expansion of a small pool of major crops and the associated homogenisation of global agricultural systems may decrease on-farm crop diversity. C_LIO_LIWe surveyed 1,369 subsistence farms stratified across climate gradients in the Ethiopian Highlands, to characterise the richness and cultivated area of the 83 edible crops they contained. We further categorise these crops by their period of introduction to Ethiopia. We apply non-metric multidimensional scaling and mixed effects modelling to characterise agrisystem composition and test the impact of crop introductions. C_LIO_LIWe find a significant positive relationship between introduced and indigenous crop richness, suggesting that crop introductions have tended to supplement rather than replace or reduce indigenous crop diversity. Geographically matched farms with higher proportions of introduced crops, had significantly higher overall crop richness. Analysis of socio-economic drivers indicates that both poverty and low accessibility are associated with reduced cultivation of modern introductions. C_LIO_LIWe conclude that global patterns of major crop expansion do not necessarily result in agrobiodiversity loss for subsistence farmers, in our Ethiopian case study. Importantly, socioeconomic factors may strongly influence the farmers propensity to adopt novel species, suggesting targets for agricultural extension policies. Given the rapid climatic, economic and demographic changes impacting global food systems and the threats to food security these entail, robust indigenous agricultural systems supplemented with diverse introduced crops may enhance resilience. C_LI

ecology↗

bioRxiv2021

Modelling potential range expansion of an underutilised food security crop in Sub-Saharan Africa

Despite substantial growth in global agricultural production, food and nutritional insecurity is rising in Sub-Saharan Africa. Identification of underutilised indigenous crops with useful food security traits may provide part of the solution. Enset (Ensete ventricosum) is a perennial banana relative with cultivation restricted to southwestern Ethiopia, where high productivity and harvest flexibility enables it to provide a starch staple for ~20 million people. An extensive wild distribution suggests that a much larger region may be climatically suitable for cultivation. Here we use ensemble ecological niche modelling to predict the potential range for enset cultivation within southern and eastern Africa. We find contemporary bioclimatic suitability for a 12-fold range expansion, equating to 21.9% of crop land and 28.4% of the population in the region. Integration of crop wild relative diversity, which has broader climate tolerance, could enable a 19-fold expansion, particularly to dryer and warmer regions. Whilst climate change may cause a 37% - 52% reduction in potential range by 2070, large centres of suitability remain in the Ethiopian Highlands, Lake Victoria region and the Drakensberg Range. We combine our bioclimatic assessment with socioeconomic data to identify priority areas with high population density, seasonal food deficits and predominantly small-scale subsistence agriculture, where integrating enset may be particularly feasible and deliver climate resilience. When incorporating the genetic potential of wild populations, enset cultivation might prove feasible for an additional 87.2 - 111.5 million people, 27.7 - 33 million of which are in Ethiopia outside of ensets current cultivation range. Finally, we consider explanations why enset cultivation has not expanded historically, and ethical implications of expanding previously underutilised species.

ecology↗

bioRxiv2021

Natural interploidy hybridization among the key taxa involved in the origin of horticultural chrysanthemums

Understanding hybridization and introgression between natural plant populations can give important insights into the origins of cultivated species. Recent studies suggest differences in ploidy may not create such strong reproductive barriers as once thought, and thus studies into cultivated origins should examine all co-occurring taxa, including those with contrasting ploidy levels. Here, we characterized hybridization between Chrysanthemum indicum, Chrysanthemum vestitum and Chrysanthemum vestitum var. latifolium, the most important wild species involved in the origins of cultivated chrysanthemums. We analysed population structure of 317 Chrysanthemum accessions based on 13 microsatellite markers and sequenced chloroplast trnL-trnF for a subset of 103 Chrysanthemum accessions. We identified three distinct genetic clusters, corresponding to the three taxa. We detected 20 hybrids between species of different ploidy levels, of which 19 were between C. indicum (4x) and C. vestitum (6x) and one was between C. indicum and C. vestitum var. latifolium (6x). Fourteen hybrids between C. indicum and C. vestitum were from one of the five study sites. Chrysanthemum vestitum and C. vestitum var. latifolium share only one chloroplast haplotype. The substantially different number of hybrids between hybridizing species was likely due to different levels of reproductive isolation coupled with environmental selection against hybrids. In addition, human activities may play a role in the different patterns of hybridization among populations.

evolutionary biology↗

bioRxiv2020

Molecular and morphological analyses clarify species delimitation and reveal a new Betula species in section Costatae

Background and AimsDelineating closely related and morphologically similar species with overlapping ranges can be difficult. Here, we use section Costatae (genus Betula) as a model to resolve species and subspecies boundaries in four morphologically similar trees: Betula ashburneri, Betula costata, Betula ermanii and Betula utilis (including ssp. utilis, and diploid and tetraploid races of ssp. albosinensis). MethodsWe genotyped 298 individuals (20-80 per species) from 38 populations at 15 microsatellite markers and a subset of 34 individuals from 21 populations using restriction-site associated DNA sequencing (RAD-seq). Morphometric analysis was conducted to characterise leaf variation for a subset of 89 individuals. Key ResultsMolecular analyses and leaf morphology found little differentiation between B. ashburneri, diploid B. utilis ssp. albosinensis and some samples of B. utilis ssp. utilis suggesting that these should be treated as a single species. By contrast, tetraploid Betula utilis ssp. albosinensis was divided into two groups with group I genetically similar to B. utilis ssp. utilis based on SNPs and group II, a very distinct cluster, which we propose as a new species, namely, Betula buggsii. Phylogenomic analysis based on 2,285,620 SNPs show a well-supported monophyletic clade of B. buggsii, forming a sister with a well-supported clade of B. ashburneri, diploid B. albosinensis and some samples of B. utilis ssp. utilis. Morphologically, Betula buggsii is characterised by elongated lenticels and a distinct pattern of bark peeling. Betula buggsii is geographically restricted to the Qinling-Daba Mountains. ConclusionsOur study reveals six genetically distinguishable species: B. ashburneri, B. buggsii, B. costata, B. utilis ssp. utilis, B. utilis ssp. albosinensis and B. ermanii. Our research demonstrates an integrative approach in delimitating species using morphological and genetic samples from their nearly entire distributions. Analyses based on subsets of species distributions may lead to erroneous species or subspecies delineation.

evolutionary biology↗

bioRxiv2020

The Distribution of Enset Pests and Pathogens and a Genomic Survey of Enset Xanthomonas Wilt

Mapping the distribution of crop pests and pathogens is essential to safeguard food security and sustainable livelihoods. However, these data are unavailable for many neglected and underutilised crops, particularly in developing countries. In Ethiopia, the worlds largest historic recipient of food aid, the indigenous banana relative enset (Ensete ventricosum) is threatened by multiple pests and pathogens whilst providing the staple starch source for 20 million people. Foremost among these is Xanthomonas Wilt of enset (EXW), caused by Xanthomonas vasicola pv. musacearum (Xvm), a globally important disease of bananas (Musa sp.) that likely originated in enset. Here we collate 1069 farm surveys to map the distribution and relative prevalence of enset pests and pathogens across the entire enset growing region. We find that EXW is the most frequently encountered pathogen, and that farmers consistently ranked EXW as the most significant constraint on enset agriculture. Our surveys also showed that corm rot, and the pests root mealybug, mole rat and porcupine are all virtually ubiquitous. Finally, we apply genotyping-by-sequencing to the detection of Xvm and demonstrate that it is present even in asymptomatic domesticated and wild enset samples, suggesting that management of plants displaying symptoms alone may not be sufficient to reduce disease transmission. Holistic understanding of pests and pathogen distributions in enset may have significant benefits for both food security in Ethiopia, and preventing proliferation in related crops such as banana across central and east Africa.

ecology↗

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↗

bioRxiv2020

Germination ecology of wild and domesticated Ensete ventricosum: Evidence for maintenance of sexual reproductive capacity in a vegetatively propagated perennial crop

O_LILoss of sexual reproductive capacity has been proposed as a syndrome of domestication in vegetatively propagated crops, but there are relatively few examples from agricultural systems. In this study we compare sexual reproductive capacity in wild (sexual) and domesticated (vegetative) populations of enset (Ensete ventricosum (Welw.) Cheesman), a tropical banana relative and Ethiopian food security crop. C_LIO_LIWe examined floral and seed morphology and germination ecology across 35 wild and domesticated enset. We surveyed variation in floral and seed traits, including seed weight, viability and internal morphology, and germinated seeds across a range of constant and alternating temperature regimes to characterise optimum germination requirements. C_LIO_LIWe report highly consistent floral allometry, seed viability, internal morphology and days to germination in wild and domesticated enset. However, seeds from domesticated plants responded to cooler temperatures with greater diurnal range. Shifts in germination behaviour appear concordant with a climatic envelope shift in the domesticated distribution. C_LIO_LIOur findings provide evidence that sexual reproductive capacity has been maintained despite long-term near-exclusive vegetative propagation in domesticated enset. Furthermore, certain traits such as germination behaviour and floral morphology, may be under continued selection, presumably through rare sexually reproductive events. Compared to sexually propagated crops banked as seeds, vegetative crop diversity is typically conserved in living collections that are more costly and insecure. Improved understanding of sexual propagation in vegetative crops may have applications in germplasm conservation and plant breeding. C_LI

ecology↗

bioRxiv2019

Micronutrient composition and microbial community analysis across diverse landraces of the Ethiopian orphan crop enset

Enset (Ensete ventricosum) is a major starch staple and food security crop for 20 million people. Despite substantial diversity in morphology, genetics, agronomy and utilization across its range, nutritional characteristics have only been reported in relatively few landraces. Here, we survey nutritional composition in 22 landraces from three enset growing regions. We present mineral characterization of enset corm tissue, free amino acid characterization of raw and processed (fermented) tissues and genomic analysis of the microbial community associated with fermentation. We show that compared to regionally important tubers and cereals, enset is high in calcium, iron, potassium and zinc and low in sodium. We report changes in free amino acid composition due to processing, and establish that the bacteria genera Acetobacter, Lactobacillus and Bifidobacterium, predominate during fermentation. Nutritional and microbial variation presents opportunities to select for improved composition, quality or safety with potentially significant impacts in food security and public health.

plant biology↗

bioRxiv2019

Genomic assessment of local adaptation in dwarf birch to inform assisted gene flow

When populations of a rare species are small, isolated and declining under climate change, some populations may become locally maladapted. Detecting this maladaptation may allow effective rapid conservation interventions, even if based on incomplete knowledge. Population maladaptation may be estimated by finding genome-environment associations (GEA) between allele frequencies and environmental variables across a local species range, and identifying populations whose allele frequencies do not fit with these trends. We can then design assisted gene flow strategies for maladapted populations, to adjust their allele frequencies, entailing lower levels of intervention than with undirected conservation action. Here, we investigate this strategy in Scottish populations of the montane plant dwarf birch (Betula nana). In genome-wide single nucleotide polymorphism (SNP) data we found 267 significant associations between SNP loci and environmental variables. We ranked populations by maladaptation estimated using allele frequency deviation from the general trends at these loci; this gave a different prioritization for conservation action than the Shapely Index, which seeks to preserve rare neutral variation. Populations estimated to be maladapted in their allele frequencies at loci associated with annual mean temperature were found to have reduced catkin production. Using an environmental niche modelling (ENM) approach, we found annual mean temperature (35%), and mean diurnal range (15%), to be important predictors of the dwarf birch distribution. Intriguingly, there was a significant correlation between the number of loci associated with each environmental variable in the GEA, and the importance of that variable in the ENM. Together, these results suggest that the same environmental variables determine both adaptive genetic variation and species range in Scottish dwarf birch. We suggest an assisted gene flow strategy that aims to maximize the local adaptation of dwarf birch populations under climate change by matching allele frequencies to current and future environments.

evolutionary biology↗

bioRxiv2019

Islands in the desert: Environmental distribution modelling of endemic flora reveals the extent of Pleistocene tropical relict vegetation in southern Arabia

Background and AimsSouthern Arabia is a global biodiversity hotspot with a high proportion of endemic desert-adapted plants. Here we examine evidence for a Pleistocene climate refugium in the southern Central Desert of Oman, and its role in driving biogeographical patterns of endemism. MethodsDistribution data for seven narrow-range endemic plants were collected systematically across 195 quadrats, together with incidental and historic records. Important environmental variables relevant to arid coastal areas, including night time fog and cloud cover were developed for the study area. Environmental niche models were built and tuned for each species and spatial overlap examined. Key ResultsA region of the Jiddat Al Arkad reported independent high model suitability for all species. Examination of environmental data across southern Oman indicates that the Jiddat Al Arkad displays a regionally unique climate with higher intra-annual stability, due in part to the influence of the southern monsoon. Despite this, relative importance of environmental variables was highly differentiated among species, suggesting characteristic variables such as coastal fog are not major cross-species predictors at this scale. ConclusionsThe co-occurrence of a high number of endemic study species within a narrow monsoon-influenced region is indicative of a refugium with low climate change velocity. Combined with climate analysis, our findings provide strong evidence for a southern Arabian Pleistocene refugium in the Omans Central Desert. We suggest this refugium has acted as an isolated temperate and mesic island in the desert, resulting in the evolution of these narrow-range endemic flora. Based on the composition of species, this system may represent the northernmost remnant of a continuous belt of mesic vegetation formerly ranging from Africa to Asia, with close links to the flora of East Africa. This has significant implications for future conservation of endemic plants in an arid biodiversity hotspot.

ecology↗