Project Description

A full project description can be found on Find a PhD. Please see below for additional information about this project:
This project will adopt a holistic approach to analyse the complex machair ecosystem and by doing so it will address multiple themes under the NERC remit, including:
  • Ecology, biodiversity & systematics
  • Plant & crop science
  • Climate & climate change
  • Genetics & development
By investigating how marine nutrients flow through the machair’s plants and pollinators to the mainland, the project encompasses three main environments: terrestrial, marine and freshwater. Furthermore, the proposed research aims to characterise key components of these environments looking at intertwined physical, chemical and biological processes. Coming to more specific QUADRAT themes, the project addresses the topic of “Biodiversity” from the point of view of ecosystem services, and ecology and conservation, as it focuses on understanding the complex interactions between the machair wildflowers and their pollinators (some of them highly endangered and recognised as high priority for conservation). The health of the machair ecosystem affects at least three important ecosystem services:
a) the stabilisation of coastal sand dunes against sea erosion;
b) the pollination of machair wildflower by insects;
c) the productivity of agricultural crops maintained by local crofters.
The project also targets “Environmental Management” for aspects related to Hydrology, Coastal Processes and Flood Management. In fact, the machair is found immediately behind coastal dunes and can be subjected to incursions by the sea during storms. Furthermore, the machair is often affected by winter flooding events caused by heavy rainfall that saturates both slacks and freshwater catchment systems inland, directly connected to the machair by rivers, lochs and lagoons. The management of this ecosystem is becoming more and more challenging, due to the nature and location of the machair, which is particularly susceptible to extreme weather events caused by climate change (rise of sea levels and flooding) and also subjected to other stressors such as human pressure, especially associated with changing agricultural practices. Local crofters have historically managed these areas with fallow breaks between crops and little herbicide use, increasing machair biodiversity and providing good pollen and nectar sources for pollinators. Recent changes in agricultural practices include shifts from organic fertilisers (seaweed) to inorganic and a shift away from traditional meadow management with a greater focus on silage production.
Essential skills
  • familiarity with R for statistical analysis of ecological data and for implementing modelling tools for Objective 4
  • previous experience of working with live animals (preferably insects) in the lab and/or in the field
  • previous experience with basic techniques of lab work from pipetting to use of centrifuges, precision scales, autoclaves and other standard lab equipment.
Desirable skills
  • previous experience of working with bumblebees (in particular of handling live bees in the lab or in the field)
  • experience with molecular work in the lab (e.g. RNA isolation, real time qPCR or basic PCR protocols)
  • expertise with soil biochemistry techniques
  • expertise with plant physiology assays.
Photo by Dr. Richard Commont at the Bumblebee Conservation Trust.

Supervisors

Fabio Manfredini

Primary Supervisor:

Profile: Fabio Manfredini
Email: fabio.manfredini@abdn.ac.uk
Institution: University of Aberdeen
Department/School: School of Biological Sciences

Paul N. Williams

Secondary Supervisor:

Profile: Paul N. Williams
Email: p.williams@qub.ac.uk
Institution: Queen's University, Belfast
Department/School: School of Biological Sciences

Lesley Lancaster

Additional Supervisor:

Profile: Lesley Lancaster
Email: lesleylancaster@abdn.ac.uk
Institution: University of Aberdeen
Department/School: School of Biological Sciences

Additional Supervisor:

Professor Robin Pakeman
Plant Ecologist
The James Hutton Institute
https://www.hutton.ac.uk/staff/robin-pakeman
robin.pakeman@hutton.ac.uk

Dr Richard Comont
Science Manager
Bumblebee Conservation Trust
https://www.bumblebeeconservation.org/our-science-research/, http://www.richardcomont.com/
Richard.Comont@bumblebeeconservation.org

References

Angus Ocean and Coastal Management (2018)
Mitchell Science of The Total Environment (2020)
Lewis Oikos (2014)

Cairns, Sarah M., Steve D. Wratten, Michał Filipiak, Emiliano R. Veronesi, David J. Saville, and Morgan W. Shields. “Ratios rather than concentrations of nutritionally important elements may shape honey bee preferences for ‘dirty water’.” Ecological Entomology (2021).

Research Methods

Proposed Research Methods.

  1. The student will adopt a systematic review approach to screen the literature and historic data on the machair (e.g. Scottish Coastal Survey, Agricultural Census, the Botanical Society of Britain and Ireland, Bees, Wasps & Ants Recording Society) to characterise how floral composition – ratio of insect-pollinated vs. wind-pollinated plants and changes in nectar and pollen availability – and pollinators communities have changed over time.
  2. The student will quantify the baseline concentrations of sodium and other nutrients (other minerals, sugar, nitrogen, phosphorus and potassium) in both the machair sand/soil and in associated plant species: these measurements will be taken across a gradient of different distances from the coastline, which will also provide a cline in salinity conditions. Furthermore, nutrients levels will be measured not only in terms of absolute concentration, but also species and stochiometric integration ratios – for example protein/sugar proportions in nectar and pollen – as these types of measures might be more important to define bumblebee preferences (4). Sodium concentrations are routinely measured in plant tissues such as leaves; the student will pilot measuring sodium in nectar and pollen and compare them with leaves. Different technologies will be used to measure nutrient levels in plant/soil samples: for example, spectroscopy analyses (e.g. ICP-AES), solid state analytical tools such as XRF or photometric multi-chemistry discrete batch robotics analysis (PMDBRA). These laboratory-based analyses will be complemented by passive sampling technologies such as DET/DGT and combination ion selective electrodes (ISE) for in situ/field chemistry characterisation. Furthermore, the student will assess how different concentrations of sodium affect the physiology of key plant species (to be identified at the start of the studentship) by measuring, for example, plant mass, floral display characteristics, amount and quality of nectar produced and reproductive performance (seed set).
  3. The student will employ three different sets of research methods: a) behavioural observations to quantify bee foraging preference for plants reared under different sodium regimes in controlled facilities; b) physiological measures (quantification of reproductive output) in response to different levels of sodium in the diet; and c) molecular analyses (quantification of differential gene expression by means of real-time PCR) to profile genes involved in the metabolism of sodium. The most suitable bee species for each assay will be selected at the beginning of the project, and multiple castes and/or individuals collected at different timepoints during the colony life cycle will be analysed.
  4. The student will develop statistical models to predict the impact on the composition of machair plant and bee communities of increasing levels of sodium as hypothesized in consequence of more frequent sea water intrusions under climate change.

 

Expected Training Provision

The machair is a unique environment localised in Western Scotland and North-west Ireland, characterised by low-level coastal grasslands usually fronted by a higher dune ridge. The machair is highly subsidised by marine resources and often connects to a wide range of freshwater bodies. Thus, machair plays an important dual role as both buffer and link between ocean and freshwater catchment systems. In addition, due to sandy soils providing relatively good agricultural potential, machair has been used extensively for arable agriculture(1).

A varied wildlife inhabits the machair, with some species of flora and fauna of high conservation priority. Of particular interest is a fascinating group of insect pollinators (bumblebees and solitary bees) that now largely depend on the machair wildflowers for their survival in the British Isles. Notably, the charismatic Great Yellow bumblebee has seriously declined in the UK and can now be found only in western and northern fringes of Scotland. These bees provide fundamental pollination services to many machair wildflowers, and therefore their survival and health is key for the preservation of the machair itself. Salt-tolerant plants (like those growing in the machair) typically accumulate high levels of sodium in their tissues and are particularly attractive and beneficial for bumblebees that normally struggle, as do all other pollinators, to gain enough sodium from their diet(2). It is possible that machair flowers provide higher sodium rewards to their bumblebee pollinators and this reinforces the complex reciprocal mutualism linking these two types of organisms.

This PhD project will investigate the complex relationship linking bumblebees and the machair from a landscape ecology and insect physiology perspective, and use this understanding to predict how future climate change and human management might impact this fragile ecosystem. The student will start their research by looking at historic data to infer how plant and pollinator communities of the machair have changed over time in different areas, and link this to recent information on nectar and pollen production by different species (OBJECTIVE 1). Some preliminary evidence suggests that insect-pollinated plants have decreased overall in the machair (with some extraordinary exceptions), while wind-pollinated plants have become more prevalent(3). The next step will be to characterise the levels of sodium and other nutrients that naturally occur in machair plants, and then test in the lab how some key plant species respond to varying levels of sodium in the environment (OBJECTIVE 2). The student will then characterise the adaptation of bumblebee pollinators to the machair, by looking at their foraging preference and their response at the molecular and physiological levels to plants reared under different sodium regimes in a common garden setup (OBJECTIVE 3). Finally, the student will combine historical, observational and experimental data from previous objectives to predict how changing environmental conditions (for example increasing sea incursions caused by climate change) will affect sodium levels in the machair and, as a consequence, the communities of local bee pollinators (OBJECTIVE 4).

 

 

 

Impact

The machair is a unique environment, being localised exclusively in Western Scotland and North-West Ireland within Europe. Therefore, any research contributing to better understanding the complex machair ecosystem has undoubtedly a strong ecological and cultural value. Moreover, other coastal environments similar to the machair are present in other parts of the globe and therefore this research will have an impact that can easily expand outside the borders of the European continent. One of the most notable examples of machair-like environments is present in New Zealand, but also other countries such as Bangladesh and Guyana present coastal areas that are subjected to sea water intrusion and are therefore threatened by climate change and could benefit from the output of this research. Furthermore, the machair is inhabited by many organisms that are at the top of the priority list for conservation in the UK: not only the insect pollinators that are at the centre of this project, but also plants (e.g. orchid species) and several birds. By characterising the ecosystem services that insect pollinators provide, this research will contribute to the preservation of all the other components of the machair ecosystem. Finally, an additional impact of this project will be to provide further evidence that the continuation of agricultural practices that local crofters perform on the machair is necessary for the continued conservation of species and preservation of the unique cultural landscape. An important part of this is to maintain the productivity of the machair soil through the use of locally sourced organic fertiliser (seaweed) rather than imported inorganic fertilisers, keeping the nutrient flow from sea to land and supporting the ecosystem services that both the machair plants and their pollinators perform.

Proposed Supervision

Details of the supervisory team. Dr Manfredini has expertise in the biology of bees and other social insects, spanning from behavioural observations in the field, to manipulative experiments in the lab and molecular work to characterize profiles of gene expression in different tissues. Dr Williams has specialisms in Soil & Environmental Biogeochemistry. Dr Lancaster provides expertise in biogeography, range shift ecology, insect physiology and statistical analysis of ecological data. Prof Pakeman has expertise in plant physiological ecology, machair and sand dune ecology, analysis of historic data and using functional traits to link management to species dynamics and trophic interactions. Dr Comont provides expertise in insect ecology and distribution, particularly of bumblebees, and in translating theoretical findings into practical conservation work.

Proposed Timetable

The first 6 month of the project will be dedicated to the systematic review of the literature and historic data (OBJECTIVE. 1). The spring and summer of YEAR 1 will focus on OBJECTIVE. 2, i.e., quantifying levels of sodium (and other nutrients) in the machair sand/soil and plants, and testing key plant species responses to varying levels of sodium in the lab/greenhouse. The following months will be dedicated to analysing these data and drafting a first paper for submission to a peer-reviewed journal – this could also include a review paper or meta-analysis of previously published work or available records in line with these data. Then, spring and summer of YEAR 2 will focus on running common garden experiments to test the behavioural and physiological responses of bumblebee pollinators to different quantities of sodium in their diet (OBJECTIVE. 3). The following autumn and winter months will be dedicated to the analysis of these data and also to performing the molecular work for gene expression analyses associated with this objective. Spring and summer of YEAR 3 will be used to collect additional data for OBJECTIVES 2 and 3 as required, and also to perform the statistical modelling analysis described in OBJECTIVE 4. The last 6 months of the studentship will be dedicated to drafting the PhD thesis and also additional papers for submission to peer-reviewed journals covering the findings of OBJECTIVES 3 and 4.

QUADRAT Themes

  • earth-systems
  • environmental-management

Partners

Bumblebee Conservation Trust

The Bumblebee Conservation Trust is a science-led organisation broadly interested in any research involving bumblebees, especially conservation-related. The Trust regularly supervises and supports under- and post-grad students, and works with academics from universities and research institutes across the UK. This PhD studentship on understanding the delicate interaction between bumblebee pollinators and the machair perfectly aligns with one of the Trust’s broad aims, to better understand bumblebees and their interactions with the environment in order to aid their conservation.  In particular it fits with a current project, “Saving the Great Yellow Bumblebee”. The project aims to better establish the current distribution and abundance of Great Yellow bumblebee in Scotland, increasing knowledge of the needs of the Great Yellow bumblebee and its use of the habitats where it is found. The findings of the PhD studentship on how nutrients flow in the machair and are assimilated/transferred through the machair flora to its pollinators will directly feeds into the full characterization of the biology of the Great Yellow Bumblebee, and thus habitat-focused conservation work.  The Trust will also benefit from the interaction with a fully dedicated research expert (the PhD student) and also with the supervisory team, whose members display a wide range of expertise that effectively complement those of the Trust’s members of staff.

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