Does competition with honeybees (Apis mellifera) adversely affect wild pollinator populations?

Summary

This PhD aims to increase understanding of the processes that drive competitive interactions between wild and domestic pollinators. This is fundamental to develop management strategies for pollination services that do not put our wild pollinators under further pressure.

Project background

Insects provide key pollination services which are vital to food production and the maintenance of semi-natural habitats. Honeybees and wild pollinators (e.g. bumblebees, hoverflies and solitary bees) occupy slightly different niches and can have divergent responses to environmental change. As a result, maintaining a diversity of wild pollinators and domestic honeybees can stabilise and enhance pollination services. With evidence mounting that declines in wild pollinators are adversely impacting agricultural yield in insect pollinated crops (Breeze et al. 2020), managed honeybees could provide a key route to mitigating pollination service deficits in both crops and wild plants. 

Competition with managed pollinators is identified amongst the cocktail of drivers of wild pollinator declines (Potts et al., 2016), and evidence is mounting that managed honeybees can adversely impact wild pollinators (e.g. Hudewenz and Klein 2015). The ecological processes driving competitive outcomes are, however, poorly understood with outcomes depending on local factors such as resource availability, the degree of specialisation of wild pollinators and the density of honeybee hives. 

Understanding the processes that drive competitive interactions between wild and domestic pollinators is fundamental to develop management strategies for pollination services that do not put our wild pollinators under further pressure. This studentship therefore aims to shed light on resource utilisation by wild pollinators and managed pollinators, under different levels of interspecific competition and resource availability. We will explore the interaction between plants and pollinators at both the functional and behavioural level to determine the impact of niche breadth and separation.

Research questions

Key aim: What are the impacts on our native pollinators of introducing colonies of honeybees into agricultural landscapes, and how does this vary with respect to colony density and resource availability?

1. Are plant and wild pollinator interaction networks changed in the presence of honeybees?

2. Does competition for forage impact on dietary niche breadth and access to floral resources? 

3. Do wild bees forage for resources differently when in the presence of honeybees?

4. Does the presence of honeybees induce a shift in forage plants in the wild bee populations?

Methodology

Methodology 

Year 1.  Paired sites, high and low densities of introduced honeybees will be compared. Focus will be on key agricultural crops that rely on insect pollination with surveying targeted to crops that flower at key points in the season. For example, apples in early spring, oilseed rape in late spring, and field beans in summer. At each site, plant pollinator interactions will be surveyed on the crop plant, and adjacent semi-natural habitat. Pollinator abundance, diversity and behaviour (e.g. location of foraging, incidence of nectar robbing) will be surveyed using transect walks and Flower-Insect Timed Counts (FIT Counts). Surveys will be conducted at different times of the day, and under different weather conditions to additionally explore niche separation with respect to temporal and environmental conditions. 

Honeybees and bumblebees gather pollen into pollen 'baskets' on their hind legs and return with them to their colonies. In the case of honeybees they return to their hive and the baskets can be harvested using pollen traps attached to the front of the hive. Honeybees fly into the trap and enter the colony via small holes which do not allow the entirety of the bee’s pollen baskets to fit. They therefore drop off into a collecting tray and can be stored prior to pollen analysis. Pollen will also be collected from wild bees across a range of habitats and plant species. Pollen analyses will determine overlap in the species of plants that wild and domestic bees are observed foraging on indicating potential for competition. A combination of traditional light microscopy and high-tech sequencing (e.g. meta-barcoding, sanger sequencing) will be used to analyse pollen. 

Year 2. Monitoring will be continued in our paired sites on crop plants and adjacent semi-natural habitat to provide a second year of data collection. Spatial datasets (e.g. UKCEH Land Cover Maps, OS Mastermap) will be used to identify key habitats present in the vicinity and floral resources in these habitats will be quantified though the season using transect walks. These data will be combined with existing datasets on nectar productivity (Baude et al. 2016) to provide an evaluation of floral resource availability in the wider landscape. 

Year 3. The final year of the PhD will see a controlled experiment which manipulates densities of managed bumblebees and honeybees (through opening and closing the nest/hive on a day-to-day basis). This will enable us to explore how the density of managed pollinators impacts on the foraging behaviour of wild pollinators. Impacts will be assessed on both crop plants and wild plants in adjacent semi-natural habitats. 

Training

A comprehensive training programme will be provided comprising both specialist scientific training and generic transferable and professional skills. A comprehensive training programme will be provided comprising both specialist scientific training and generic transferable and professional skills. The student will receive training in entomology and field ecology, and in collecting, analysing and interpreting spatial data. Plant and invertebrate taxonomic skills are increasingly rare in the scientific community. Additionally the student will have the opportunity to work across institutes and learn innovative meta-barcoding/sequencing techniques. The student will have the opportunity to work with land managers and others to raise awareness of the value of pollinators. 

Requirements

Candidates should have a strong academic background in ecology or a related biological discipline.