Biologists and conservationists have long been interested in the study of island populations which may face genetic bottlenecks due to predicted smaller population sizes and barriers to gene flow. This can be especially detrimental for organisms, such as bumblebees, which have haplodiploid sex determination whereby males develop from unfertilised (haploid) eggs while females develop from fertilised (diploid) eggs. Reductions in population size can increase inbreeding, leading to the production of sterile diploid males and further contributing to local extinction events.
The white-tailed bumblebee complex (Bombus lucorum agg) is an ideal case study for investigations of gene flow. While the complex is generally considered to be a geographically widespread group of little conservation importance, it has been argued that the three cryptic species that make up the complex – B lucorum, B magnus, and B cryptarum – each have smaller ranges and thus are potentially vulnerable to local extinctions.
To better understand the genetic diversity maintained in island and mainland populations of the complex, and therefore their resilience to local extinctions, this project sampled non-reproductive specimens from five of Scotland’s islands representing three distinct island regions (Inner Hebrides: Isle of Coll, Isle of Tiree; Outer Hebrides: North Uist, South Uist; and Orkney Islands: Sanday) in 2023 and two adjacent mainland locations (Oban and Ullapool) in 2025 using resources provided by the Charles Sutherland Scholarship. In the next few months whole genome sequencing (WGS) techniques will be applied to these samples to determine: 1) if there is gene flow across the islands and with the Scottish mainland and 2) if there is evidence for adaptation in the genomes of island populations. Characterisation of the population structure at a genomic level of these ecologically key bumblebees will help us assess and develop strategies that meet their conservation needs. This is especially important given documented global declines.
Climate and habitat change are two of the most critical issues affecting the survival and persistence of communities of wild pollinators worldwide. The coastal habitats of the British Isles are particularly vulnerable to these phenomena for geographic and historical reasons. Consequently, several species of bumblebee have disappeared or are in extreme decline. This analysis will help us better understand the adaptive potential and evolutionary history of isolated populations, describe emerging environmental risks to population resilience, and identify potential conservation targets. Findings will be combined with data on the foraging ecology and nutrition of these island populations to help identify strategies for conservation of endangered and declining species inhabiting Scottish coastal habitats.
