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• Cobb, Lauren Louise; Sydenham, Markus A. K.; Nielsen, Anders & Star, Bastiaan (2026). Significant fine-scale population differentiation in two common bumblebee species (B. pascuorum and B. lapidarius) detected in Northern Europe. Heredity. ISSN 0018-067X. p. 1–14. doi: 10.1038/s41437-026-00873-2. Full text in Research Archive Show summary

  Bumblebees are keystone pollinators which facilitate the reproduction of a wide range of wild and agricultural plants. Their abundance and diversity have been severely reduced by anthropogenic stressors such as widespread land-use change and habitat fragmentation. However, we lack a comprehensive understanding of population structure and local adaptation in bumblebees inhabiting human-altered landscapes. Here, we discover significant fine-scale (e.g. ~300 km) population structure within two common bumblebee species, Bombus lapidarius and Bombus pascuorum, by analysing whole genome data of 106 specimens from 7 sites in northern Europe. While the observed population structure is largely associated with natural oceanic barriers, we also detect significant divergence between populations sampled from anthropogenic landscapes which are not separated by such barriers. Furthermore, whereas genetic divergence in B. lapidarius is spread relatively evenly across the genome, divergence in B. pascuorum is concentrated within several megabase-sized genomic regions—including a putative chromosomal inversion – which may underlie well-known colour polymorphisms across its range. Our observations reveal a distinct genomic architecture underlying population structure within these bumblebee species, and highlight the necessity of increasing our understanding of bumblebee connectivity to design optimal bumblebee conservation strategies.

• Cobb, Lauren Louise; Muinck, Eric de; Kollias, Spyridon; Skage, Morten; Gilfillan, Gregor & Sydenham, Markus A. K. [Show all 8 contributors for this article] (2024). High-throughput sequencing of insect specimens with sub-optimal DNA preservation using a practical, plate-based Illumina-compatible Tn5 transposase library preparation method. PLOS ONE. 19(3). doi: 10.1371/journal.pone.0300865. Full text in Research Archive Show summary

  Entomological sampling and storage conditions often prioritise efficiency, practicality and conservation of morphological characteristics, and may therefore be suboptimal for DNA preservation. This practice can impact downstream molecular applications, such as the generation of high-throughput genomic libraries, which often requires substantial DNA input amounts. Here, we use a practical Tn5 transposase tagmentation-based library preparation method optimised for 96-well plates and low yield DNA extracts from insect legs that were stored under sub-optimal conditions for DNA preservation. The samples were kept in field vehicles for extended periods of time, before long-term storage in ethanol in the freezer, or dry at room temperature. By reducing DNA input to 6ng, more samples with sub-optimal DNA yields could be processed. We matched this low DNA input with a 6-fold dilution of a commercially available tagmentation enzyme, significantly reducing library preparation costs. Costs and workload were further suppressed by direct post-amplification pooling of individual libraries. We generated medium coverage (>3-fold) genomes for 88 out of 90 specimens, with an average of approximately 10-fold coverage. While samples stored in ethanol yielded significantly less DNA compared to those which were stored dry, these samples had superior sequencing statistics, with longer sequencing reads and higher rates of endogenous DNA. Furthermore, we find that the efficiency of tagmentation-based library preparation can be improved by a thorough post-amplification bead clean-up which selects against both short and large DNA fragments. By opening opportunities for the use of sub-optimally preserved, low yield DNA extracts, we broaden the scope of whole genome studies of insect specimens. We therefore expect these results and this protocol to be valuable for a range of applications in the field of entomology.

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• Cobb, Lauren Louise & Star, Bastiaan (2025). Bumblebees in fragmented landscapes: Using population genomics and bioclimatic models to explore spatial connectivity in three bumblebee species. Universitetet i Oslo. Full text in Research Archive Show summary

  Bumblebee pollination is an integral facet of the temperate terrestrial ecosystem, facilitating the reproduction of a multitude of wild plants and agricultural crops. Contemporary human activity has however become a planet-shaping force from which vast portions of the biosphere are at serious risk, including these ecologically crucial insects. Recent alarming declines of a range of bumblebee species have been attributed to several of such anthropogenic drivers, particularly habitat degradation and loss due to land-use intensification, pollution, and climate change. The resulting reductions in bumblebee abundance can often be compounded by the accompanying effects of range fragmentation, such as population isolation and erosion of genetic diversity, which massively increase extinction risk. Assessing and understanding the impacts of habitat fragmentation on bumblebee biology is therefore of urgent conservation concern. In this thesis, I make use of population genomics methods and habitat suitability modelling to examine the levels of dispersal, gene flow and connectivity in three bumblebee species – Bombus lapidarius, Bombus pascuorum and Bombus consobrinus – across the anthropogenically disturbed matrix of the Scandinavian peninsula. Chapter I considers a fundamental methodological challenge for this project: how to efficiently and cost-effectively generate sequence data of sufficient quality for genomic analyses from very small, biologically valuable insect tissue samples, while causing minimal specimen damage? This question is addressed through the development of a streamlined library preparation and post-amplification clean-up protocol, with which we generate the data that makes up the remainder of this thesis. In Chapter II, the genomic variation of the B. lapidarius and B. pascuorum populations which inhabitat the Scandinavian peninsula is investigated, revealing low but significant levels of population structure despite the broad abundance and distribution of both species. We also observe patterns of decreasing genetic diversity With increasing latitude, which may be indicative of evolutionarily recent post-glacial colonisation. In addition, we detect several highly divergent genomic regions, the most prominent of which is hypothesised to represent a megabase-scale chromosomal inversion in B. pascuorum, a biological feature as yet unheard of in bumblebees. Chapter III provides an ecological context for these results through the integration of habitat suitability models, generated using several bioclimatic variables, with our B. lapidarius and B. pascuorum sequence data. Our models indicate that bumblebee abundance is increased by grasslands and deciduous forests and decreased by coniferous forests and agricultural land, and are significant predictors of broad-scale bumblebee genomic similarity. Additionally, we detect a pattern of fine-scale isolation by distance in B. lapidarius. Finally, we turn our attention to the montane foraging specialist B. consobrinus in Chapter IV, conducting a fine-scale population genomics study across the area surrounding the Hardangervidda mountain plateau of inland Norway. Despite its constrained foraging ecology, B. consobrinus exhibits very little population structure, but measures of genetic diversity indicate recent population contraction and may suggest restricted dispersal and gene flow between our samples and subpopulations beyond our study range. By shedding light on the population connectivity of these three crucial pollinators, this thesis provides fresh scientific understanding for the broader aim of bumblebee conservation in the face of ongoing anthropogenic environmental change.

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