Highlight: Museum collections reveal loss of genetic diversity in declining bumblebee populations

Taking a car trip through the countryside is an experience starkly different from what it was a few decades ago: for one, windshields are increasingly devoid of squashed insects. Growing reports of drastic declines in insect populations—vital for ecosystem processes ranging from pollination and nutrient processing to acting as links in food webs—are ringing alarm bells for conservation biologists still struggling for data on long-term population trends (Goulson 2019). Even less is known about the scale of genetic diversity loss that accompanies the declines of insects. Knowing a population's level of genetic diversity can inform conservation biologists about how environmental changes affect a species’ adaptive capacity. It is nevertheless essential to have a baseline against which to compare current levels of genetic diversity.

“Natural history collections potentially give us that missing historical baseline,” says Victoria Mullin, professor at Trinity College Dublin (Ireland), mentioning that “there are tens of millions of insect specimens in UK collections alone, many dating back well over a century.” Ian Barnes, professor at the Natural History Museum (United Kingdom), adds that “as sequencing becomes cheaper and methods for recovering DNA from museum specimens improve, we should increasingly be able to reconstruct changes in genetic diversity through time, rather than simply measuring it from the present day onwards.”

In a new article now published in Molecular Biology and Evolution (Mullin et al. 2026), Mullin and Barnes’ team tested this approach. Mullin et al. (2026) sequenced the genomes of 130 specimens of the moss carder bumblebee (Bombus muscorum; Fig. 1a) sampled across Britain between 1890 and 2019. The moss carder bumblebee is an important pollinator of grasslands across Eurasia. Still, its range has been contracting in Britain: once widespread, it is now mostly confined to northern territories in Scotland (Fig. 1b). The authors hypothesized that tracking changes in genetic diversity throughout the past century could reveal how shifts in land use impacted populations of this pollinator.

Figure 1.

Museum genomics reveals the decline of genetic diversity in the moss carder bumblebee (Bombus muscorum) across most of Britain: (a) specimen of moss carder bumblebee; (b) photo of an open grassland in the Scottish Hebrides, the typical habitat of this pollinator species; (c) specimens of moss carder bumblebee from a museum collection. Historical collections such as this one provide important reservoirs of temporal genetic information. Photos by Gavin Broad (CC BY 4.0).

After sequencing the genomes of historical and contemporary samples and analyzing their genetic diversity, Mullin et al. (2026) were surprised by the magnitude of the change: between 1890 and 2019, heterozygosity declined by over 30%. “We weren’t sure what to expect but, when the results came through, the scale of the change was certainly a shock,” reveals Mullin; she adds that “although we knew that the numbers of moss carder bumblebees have been declining in recent years, it is always hard to know if that will result in a change which can be measured at the genome level.”

The authors found that reduced genetic diversity was associated with increased inbreeding. Throughout the genome, the median length of runs of homozygosity (ie stretches of the genome without heterozygous loci) almost tripled. This effect was not spatially uniform. Rather, samples collected post-1975 in southern Britain (England and Wales) had significantly longer runs of homozygosity than contemporary Scottish samples; the latter retain diversity levels comparable to pre-1926 samples.

To Barnes, this difference in diversity among contemporary samples likely reflects the heterogeneous changes in land use in Britain throughout the 20th century. “Scotland has retained larger and more continuous areas of flower-rich open grassland habitat, which is particularly true for the beautiful machair habitats found in the Outer Hebrides and Highland regions where this species is most common,” Barnes says, countering that “in England and Wales, the populations are now restricted to more isolated coastal remnants, due to agricultural intensification and wetland drainage.”

Mullin et al. (2026) demonstrate how leveraging museum collections as a source of temporal genetic data can become a cornerstone approach in conservation genomics (Fig. 1c). Beyond insights into temporal and spatial patterns of genetic variation, genetic data from museum specimens can be crucial for even basic species identification: almost a quarter of the moss carder bumblebee specimens sequenced by Mullin et al. (2026) were individuals from other species. Mullin warns that “if that level of misidentification is occurring in field surveys then it could have a substantial impact on estimates of species distribution.”

More broadly, Mullin et al. (2026) reaffirm the vital role of museum collections in meeting conservation targets. As Barnes states, “the Global Biodiversity Framework requires countries to maintain and restore genetic diversity within and between populations of wild species, but for most of them we have very little idea what their genetic diversity looked like before recent environmental change.” Going forward, Mullin, Barnes, and their team hope to extend this approach to other insect species that provide important ecosystem services beyond pollination.

Want to learn more? You can check out other articles on museomics recently published in Molecular Biology and Evolution:

• “Pangolin museum genomics reveal the dynamic genetic consequences and extinction risk of the critically endangered Chinese pangolin” (Hu et al. 2026)

• “Novel 20th century rotavirus alphagastroenteritidis strains identified in formalin-fixed and ethanol-preserved museum specimens” (Porter et al. 2026)

• “Historic museum samples provide evidence for a recent replacement of Wolbachia types in European Drosophila melanogaster”(Strunov et al. 2023)

Funding

None declared.