Well Tempered podcast

Scholar Series: Dr. Sarah Arnold, Behavioral Entomologist at the Natural Resources Institute

07/02/2020
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Podcast episode description: Dr Sarah E J Arnold is a Senior Lecturer in Insect Behavior and Ecology at the Natural Resources Institute (NRI), University of Greenwich, UK, primarily focusing on pest behavior, chemical ecology, and ecosystem services.

After completing her PhD in sensory ecology in the Chittka Lab at Queen Mary, University of London, Dr. Arnold joined the University of Greenwich in 2010. Since joining NRI (a specialist research, development and education organization of the University of Greenwich), she has continued to develop her interest in pollinators, studying different aspects of how their environment may influence their behavior and health. She has published in areas including the role of pollen composition and nectar chemistry in pollinator performance, the importance of environmental characteristics of farms in affecting pollinator populations, and different aspects of their foraging and flower-finding behavior. She is particularly interested in how farms and other habitats can be managed to support pollinators’ needs better. As she works on both pest and beneficial insects, she rears various species of insects in the laboratory to explore their behavior and life history.

Her work has appeared in international peer-reviewed journals, including papers on flower color evolution, insect ecology, and pollinator and storage pest behavior, and is one of the developers and managers of the Floral Reflectance Database (FReD). One of her latest projects, involving Caribbean fieldwork in conjunction with the University of Trinidad and Tobago and the Cocoa Industry Board of Jamaica - both areas with low yields of high quality fine flavor cacao - investigated the possibility of optimized production of Theobroma cacao via pollination by various Ceratopogonid species. Read on at the project website CocoaPop.

More about Dr. Arnold’s work and projects can be accessed here.

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Dr. Sarah Arnold. Photo uploaded with permission from Dr. Sarah E J Arnold

Themes discussed in this episode:

- What pollinates a cacao flower?
- Midges are part of the Ceratopogonidae family, a group of of flies measuring 2-3 mm long
- Ecology of midges; difficulties of breeding and physical discovery
- Pollinator behavior according to country/landscape of origin
- Attributes of a good pollinator; pick up the pollen, move to another flower (perhaps on another tree)
- Cacao self-incompatibility; meaning it prevents itself from self-fertilization
- Shape, odor, and complexity of the cacao flower; appeal for both humans and insects
- Diverse family genus of flowering plants, Malvaceae, includes: durian (pollinated by bats), cotton, okra
- Plant plasticity
- Cacao in greenhouses and botanical gardens; at Kew Palm House in the UK, Theobroma cacao has successfully grown there, pollinated either by midges or another species;

“It seems like the (cacao) tree needs the midges much more than midges need the tree.”

- Questions she asked in her research: what pollinators are present? How does this population change over the year? And how that might match when the crop is in peak flower?

- Samantha Forbes; a colleague from Australia, who was helpful in studies regarding rearing cocoa midges over generations in a laboratory setting.
—> For their project, it was the first known time midges from a cacao plantation were bred for months at a time, running over multiple generations. Previously eggs and larvae had been captured and raised to adulthood.
- Complications of recreating the bacterial conditions of the farm environment in a lab; mimicking banana pseudostem
- Pollinator life-cycles; midges lay their eggs in rotten material, generally the detritus of cacao pods
- Pollination rates of the midges; ~5% of the cacao flowers will be successfully pollinated. While they are present, their numbers are not abundant in the wild, however they are apt at transmitting pollen, generally in 1-2x visits to the flower.

“...working out the perfect level of pollination to optimize yield and optimize it sustainably from a cocoa farm, is an area of continuing research that is very important at the moment.”

- Hand-pollination. Is it viable?
- Effect of climate change on biodiversity in pollinators; potential population loss due to drought and heat waves.
- Farmers and pollinators — offering habitats, working together
- Methodologies for obtaining lab results for odor compounds; most drawing on studies from almost 40 years ago.
- Professor David Hall, Professor of Chemical Ecology , and general expert on all things involving the chemistry of scents.
- Testing natural floral odor versus a synthetic blend for attractiveness to pollinators.

Additional:
If research continues — Dr. Arnold says, it will be interesting to see if wild flowers have evolved differently; might they be more disease resistance? Produce higher yields, or will flavor develop distinctly? These things will greatly inform future breeding programs.

Where to find Dr. Arnold:

Twitter @sejarbold

Where to find Lauren, host of Well Tempered Media productions and chocolate maker at WKND Chocolate:
Instagram: @wkndchocolate
Twitter: @wkndchocolate
Articles, podcasts, chocolate recipes, and Conversations in Cocoa at laurenonthewknd.substack.com

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