Ecology and function of buzz-pollination in bumblebees

Overview: Some bees are capable to use high-frequency vibrations to remove pollen from flowers, in a phenomenon known as buzz-pollination1. Buzz-pollinated plants have evolved multiple times across different plant groups, and include some important crops such as tomatoes and potatoes (Solanum). Despite the widespread distribution of buzz-pollinated flowers, and the potential importance of this pollination mechanism for both natural and agricultural systems, the ecology and function of buzz-pollination is not well understood.
Here we propose to study buzz-pollination in bumblebees in order to understand the mechanisms that allow bees to produce these high frequency vibrations, as well as the ecological and evolutionary context in which these vibrations are produced. We will study buzz-pollination in natural and experimental settings to address the following specific research questions: i. Do different species of bees produce different types of vibrations? ii. Are different types of flowers “tuned” to different vibrations? iii. What is the relationship between flower morphology, reproductive strategy (mating system) and optimal frequency? iii. Can bees adjust the frequency of their vibrations depending on the type of flower they visit? iv. What is the effect of environmental stressors on buzz-pollination and plant reproductive success?
To investigate whether different species of bees produce different types of vibrations, the student will conduct observations of UK pollinators (bumblebees), and records the vibrations produced when visiting familiar and novel buzz-pollinated plants. The comparison of the acoustic signature of vibrations produced by different bees on different plants will generate the data needed to address questions i and ii.
Flower morphology and mating system are closely related. Given that the effect of vibrational forces on pollen release depends on flower (anther) morphology, we predict that species that are regularly cross-fertilised will have different vibrational properties compared to self-fertilised species. To test this we will use species of Solanum (Solanaceae) that differ in mating system. Solanum comprises more than 1200 species with diverse mating systems and is a genus well-known for being buzz-pollinated. Our lab at the University of Stirling has a large collection of Solanum species that will be used for this component of the project. In addition to wild accessions, we will also study the pollination of agricultural species, namely Solanum lycopersicon (tomato).
Next, we will develop genetic markers (microsatellite and other length-based polymorphisms) in order to measure the relative rate of selfing and outcrossing in natural populations, and to conduct paternity analysis of experimental populations. This component of the project will allow us to simultaneously characterise natural populations and develop the tools to measure the efficiency of buzz-pollination (using both female and male components of fitness) in field trials.

Finally, by using captive colonies of bumblebees in controlled conditions (flight arenas and field experiments), we will investigate the extent to which individual bees are capable to change the type of vibrations they produce in relationship to increasing experience in handling buzz-pollinated flowers, as well as depending on the morphology of the flower being visited. We will also assess whether buzz-pollination characteristic are affected by the health of the bumblebee colony. We will generate different treatments of “colony stress” by manipulating the number of workers, and applying different levels of exposure to commercial pesticides. Our field experiment will study both the vibrations produced by bees, and the consequences of changes in buzz-pollination patterns on plant reproductive success (estimated via both male and female fitness). Whether the type of vibration produced by bees is fixed in each individual, or whether it can be dynamically adjusted has important implications for pollination of natural and agricultural systems. Furthermore, the extent to which stressors such as pesticide exposure affect pollination efficiency will provide a valuable insight into the potential risks of current agricultural practices on both bumblebees, and ultimately on plant reproductive success.
We will take advantage of the plant growth facilities available at the University of Stirling. These include controlled environment cabinets and walk-in rooms that allow us to bring to flower multiple species with different growth requirements. The ability to grow plants year-round is essential for completing the proposed breeding program. Genotyping will be done in the DBS Genomics facility at Durham University.

Deadline for applications: 05 January 2016
To apply: Please send your CV and a letter of why you are ideally suited for this project to: [Email Address Removed]. No letters of support are needed at this stage. Application deadline: 5 January 2016. Informal queries are welcome.
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