Floral preferences of bumblebees across a range of European climates

Overview

Background. Bumblebees are agriculturally important pollinators, but are currently declining in abundance in the UK and around the world, in part due to climate change (Soroye et al. 2020). Understanding these declines requires research on the biology and ecology of these species. Bumblebees are thought to be generalists, pollinating a variety of flower species. However, our preliminary observations conducted in Durham in summers 2020 and 2021 indicate that different bumblebee species prefer different plants (see also Sikora et al. 2020). Bumblebees have been a preferred insect model for neuroethology and sensory neuroscience, and a wealth of earlier work has focussed on the importance of visual cues and nectar/pollen reward for foraging honeybees and bumblebees (Latty and Trueblood 2020). In contrast, the importance of floral smells is less well known, although some works report the essential role of flower volatiles in bumblebees’ floral choice (Galen and Kevan 1983; Suchet et al. 2011; Haber et al. 2019). This project will investigate olfactory preferences of commonly occurring bumblebees (e.g. Bombus terrestris, Bombus pascuorum and Bombus lapidarius) to naturally-occurring floral volatiles, and how these preferences are affected by climatic conditions and background plant communities in Norway (Kløfta), UK (Durham and Stirling), Germany (Würzburg), Italy (Milan) and Portugal (Braganca). We expect the plants that the bumblebees forage on to differ between these location, due to different climatic condition. We hypothesise that, despite the differences in plant species, the key components of floral bouquets will be very similar across test locations.
Aims. 1) To identify plants that bumblebees forage on in the five countries, to establish plant preferences for bumblebee species; 2) Collect floral volatiles from the plants identified in Aim 1, as well as florals that bumblebees do not forage on, as controls; analyse these volatiles by GC/MS ; 3) Establish behavioural preferences of bumblebees in response to full floral bouquets and components of bouquets, fractions and synthetic components of that are specific for focal plant species.

Methodology

Bee and plant collections will be conducted in the areas around Durham, Stirling, Kløfta, Würzburg, Milan and Braganca in March-September during the local bumblebee foraging periods. The student will be advised and assisted during field collection by OR and local members of the supervisory team. Student will be trained to identify plants (by MVM and WD) and bumblebees (by OR, VN and CP) via morphological cues and DNA barcoding. Floral volatiles will be collected at the same time as bumblebees by using standard volatiles traps, and will be analysed by the student via gas chromatography-mass spectrometry in TS laboratory. Behavioural olfactory assays on bees will be conducted in the field or either in the glasshouse at the Biocentre, University of Würzburg (facilitated by TS) or in a glasshouse at Durham Botanical garden (facilitated by WD). The bees will be given a choice between 2 stimuli, or stimulus and a control, and their preference for a smell will be inferred from the tendency of a bee to land at the stimulus.

Project Timeline

Year 1

Year 1, M1-6: Conduct literature review, learn to rear bumblebee Bombus terrestris colonies, design behavioural experiments, learn to collect and analyse GC/MS data, Attend a winter school/course; M7-12: Collect and identify bees and plants and collect volatiles for Aims 1-2

Year 2

Year 2, M1-6: Work in Würzburg and Durham to analyse collected volatiles, M7-12: continue field collections as necessary for Aims 1-2, collect bumblebees for Aim 3 and assay their behaviour, Attend a European conference

Year 3

Year 3, M1-6: Analyse field data from Y2; M7-12: Conduct field collections and behavioural experiment on wild-caught and lab-reared bees, Attend an international conference;

Year 3.5

Year 4, M1-6: Write thesis

Training
& Skills

The student will receive training: 1) by supervisors with complementary skills and expertise; 2) by collaborators and postdocs in the seven participating institutions; 3) by attending summer courses, conferences and Durham-run training events; 4) by participating in regular public outreach activities; 5) by helping OR to supervise UG students; 6) by presenting their work at lab meetings and conferences. The student will acquire knowledge and skills in: 1) insect chemical ecology and neuroethology; 2) gas chromatography/mass spectrometry and collection of volatiles; 3) bumblebee rearing; 4) identification of bumblebees and plants; 5) molecular biology methods; 6) cutting-edge techniques for behavioural analysis; 7) presentation and scientific writing; 8) research supervision; 9) Impact and public outreach.

References & further reading

Galen C, Kevan PG (1983) Bumblebee foraging and floral scent dimorphism: Bombus kirbyellus Curtis ( Hymenoptera: Apidae) and Polemonium viscosum Nutt. ( Polemoniaceae). Can J Zool 61:1207–1213. https://doi.org/10.1139/z83-164
Haber AI, Sims JW, Mescher MC, et al (2019) A key floral scent component (β-trans-bergamotene) drives pollinator preferences independently of pollen rewards in seep monkeyflower. Funct Ecol 33:218–228. https://doi.org/10.1111/1365-2435.13246
Latty T, Trueblood JS (2020) How do insects choose flowers? A review of multi‐attribute flower choice and decoy effects in flower‐visiting insects. J Anim Ecol 1365-2656.13347. https://doi.org/10.1111/1365-2656.13347
Raines K, Whitehorn P, Copplestone D, Tinsley M (2020) Chernobyl-level radiation exposure damages bumblebee reproduction: a laboratory experiment. Proc R Soc B
Sikora A, Michołap P, Sikora M (2020) What kind of flowering plants are attractive for bumblebees in urban green areas? Urban For Urban Green 48:126546. https://doi.org/10.1016/j.ufug.2019.126546
Soroye P, Newbold T, Kerr J (2020) Climate change contributes to widespread declines among bumble bees across continents. Science (80- ) 367:685–688. https://doi.org/10.1126/science.aax8591
Suchet C, Dormont L, Schatz B, et al (2011) Floral scent variation in two Antirrhinum majus subspecies influences the choice of naïve bumblebees. Behav Ecol Sociobiol 65:1015–1027. https://doi.org/10.1007/s00265-010-1106-x

Further Information

Informal enquiries are strongly encouraged and should be directed to Dr Lena Riabinina, olena.riabinina@durham.ac.uk, +44-191-334-1282

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