Biology subjects

Hollingsworth, P. M.

Publications and source records attributed to Hollingsworth, P. M..

4 recordsLinked to original sources

bioRxiv2026

Rubber mapping reveals opportunities and current limitations of deforestation due-diligence

Commodity maps and the ability to monitor commodity-driven deforestation are essential for sustainability risk assessment and due diligence. Natural rubber (Hevea brasiliensis), used primarily in tyres, remains challenging to map because of its similarity to other tree cover. Integrating optical and radar satellite data, we produced a 10 m map of rubber distribution in Southeast Asia for around 2020 and assessed this map and similar products for deforestation due diligence. In continental Southeast Asia, estimated users accuracy was 0.95 and area-adjusted producers accuracy 0.78. Rubber-associated clearances of natural and semi-natural tree cover during 2011-2016 were estimated at 0.3-0.4 Mha, predominantly associated with industrial-scale plantations and concentrated in Cambodia. Historical clearances were less certain, with plausible bounds of 1.3-3.0 Mha since 1990. Evaluation of rubber and forest maps highlighted persistent limitations, particularly in insular Southeast Asia and smallholder systems. Accounting for these limitations is critical for fair and effective due diligence.

ecology↗

bioRxiv2023

Genomic clustering by geography not species in taxonomically complex British and Irish eyebrights (Euphrasia)

Genomic studies of incipient speciation are fundamental to understand the origin and establishment of species. However, a wide range of evolutionary processes and complex evolutionary interactions remain to be explored outside of genetically tractable evolutionary and ecological model systems. Here, we study taxonomically complex British and Irish eyebrights (Euphrasia), as a test case for how different evolutionary factors influence species boundaries across geographic space. Euphrasia is a plant genus that has remarkable diversity in ploidy, mating system and ecology. There are 21 British and Irish Euphrasia species, but with species that are exceptionally difficult to identify based on morphology or DNA barcoding. Here, we test the hypothesis that species boundaries are highly permeable, and taxa experience extensive gene flow despite potential barriers such as ploidy and contrasting mating systems. To understand geographic genetic structure and the nature of species differences, we applied genotyping-by-sequencing (GBS) and spatial-aware clustering methods to 378 population samples from 18 British and Irish species. We find the selfing heathland specialist E. micrantha demonstrates genome-wide divergence in Northern Scotland, indicative of a distinct post-glacial colonisation history and the role of a highly selfing mating system in divergence. In contrast, all other genetic clusters correspond to geographic regions, with extensive gene flow between species and a complete absence of species-specific SNPs. Our results reveal the highly permeable species boundaries present in a recently diverging group, with an overriding signal of geographic genetic structure over and above genetic clustering by species.

evolutionary biology↗

bioRxiv2022

New high-resolution maps show that rubber causes significant deforestation

Understanding the impacts of cash crop expansion on natural forest is of fundamental importance. However, for most crops there are no remotely-sensed global maps1, and global deforestation impacts are estimated using models and extrapolations. Natural rubber is an example of a major commodity for which deforestation impacts have been highly uncertain, with estimates differing more than five-fold1-4. Here we harnessed earth observation satellite data and cloud computing5 to produce the first high-resolution maps of rubber and associated deforestation covering all Southeast Asia. Our maps indicate that rubber-related forest loss has been significantly underestimated in policy, by the public and in recent reports6-8. Our direct remotely-sensed observations show that deforestation for rubber is two to threefold higher than suggested by figures currently widely used for setting policy4. With over 3.76 million hectares of forest loss for rubber since 1993 (2.77 [2.5-3 95% CI] million hectares since 2000), and over 1 million hectares of rubber plantations established in Key Biodiversity Areas, the impacts of rubber on biodiversity and ecosystem services in Southeast Asia are extensive. Thus, rubber deserves more attention in domestic policy, within trade agreements and in incoming due diligence regulations.

ecology↗

bioRxiv2017

DNA barcoding British Euphrasia reveals deeply divergent polyploids but lack of species-level resolution

Background and aimsDNA barcoding is emerging as a useful tool not only for species identification but for studying evolutionary and ecological processes. Although plant DNA barcodes do not always provide species-level resolution, the generation of large DNA barcode datasets can provide insights into the mechanisms underlying the generation of species diversity. Here, we use DNA barcoding to study evolutionary processes in taxonomically complex British Euphrasia, a group with multiple ploidy levels, frequent self- fertilization, young species divergence and widespread hybridisation.\n\nMethodsWe sequenced the core plant barcoding loci, supplemented with additional nuclear and plastid loci, in representatives of all 19 British Euphrasia species. We analyse these data in a population genetic and phylogenetic framework. We then date the divergence of haplotypes in a global Euphrasia dataset using a time-calibrated Bayesian approach implemented in BEAST.\n\nKey resultsNo Euphrasia species has a consistent diagnostic haplotype. Instead, haplotypes are either widespread across species, or are population specific. Nuclear genetic variation is strongly partitioned by ploidy levels, with diploid and tetraploid British Euphrasia possessing deeply divergent ITS haplotypes (DXY = 5.1%), with haplotype divergence corresponding to the late Miocene. In contrast, plastid data show no clear division by ploidy, and instead reveal weakly supported geographic patterns.\n\nConclusionsUsing standard DNA barcoding loci for species identification in Euphrasia will be unsuccessful. However, these loci provide key insights into the maintenance of genetic variation, with divergence of diploids and tetraploids suggesting that ploidy differences act as a barrier to gene exchange in British Euphrasia, with rampant hybridisation within ploidy levels. The scarcity of shared diploid-tetraploid ITS haplotypes supports the polyploids being allotetraploid in origin. Overall, these results show that even when lacking species-level resolution, DNA barcoding can reveal insightful evolutionary patterns in taxonomically complex genera.

evolutionary biology↗