Pollinators and the Art of Choice: Navigating the Chemistry of Floral Rewards (Ep. 48)

Have you ever wondered why bees don’t always choose the flowers that seem to offer the best buffet of nectar and pollen? Dr. Claire Hemingway has been studying the complex decisions bees make as they navigate a landscape blooming with options. Her research reveals that the choices bees make are not as straightforward as we might assume. Just like us in a grocery store, bees weigh their decisions based on a variety of factors, including their recent experiences and the availability of other floral options.

Claire is an Assistant Professor at the University of Tennessee in the US. You can read more about the study we discussed here or check out her lab, which focuses on decision-making strategies in complex environments.

Good to know

Claire used nectar as the bees’ reward in her experiments. Bees need nectar for energy and flowers produce nectar as a reward for pollination; to encourage bees to visit and take some pollen with them when they leave.

Transcript

[00:00:00] Welcome to The Bee’s Knees, a podcast wild about native bees. Wild and native bees are under threat worldwide. In each episode, we look at actionable things we can do to support these adorable little guys whose pollination work is crucial for maintaining biodiversity. I’m Jacy Meyer, and I thank you for being here.

When confronted by the multitude of choices in your local grocery store, how do you choose what to buy? Typically, if you’ve liked a brand in the past, you feel confident you’ll like it again. and go with the known option. But what about bees? When they are met with a meadow of wildflowers, how do they choose which ones to visit?

That’s what we’re talking about today with Dr. Claire Hemingway, whose research focuses on animal cognition. I started our conversation by asking Claire to explain the research her and her team did and what they wanted to know. Yeah, so my research group is [00:01:00] really interested in how animals make decisions between multi attribute multi alternative decision tasks.

So, uh, this is really relevant for pollinators, um, such as generalists, bumblebees and honeybees that are having to make decisions between multiple flowers the same time that are all characterized by multiple attributes in terms of reward quality. And so, in this review, we wanted to summarize some of the recent empirical work that’s been done in this field and highlight some of the areas for future research, because we think that this is a really.

Robust area for projects to sort of build on and we’ll have some really interesting implications for how we think about pollinator cognition and plant pollinator interactions. Can you share how flower traits like smell, color, and patterns help bees find food? And what have your experiments shown about this?

Yeah, so flowers have been termed billboards of sensory information and I think that that’s a really Appropriate way to describe them. They’re often multimodal, so they can [00:02:00] vary in their visual components, like color, shape, size, they can vary in their olfactory components, the smells that they emit to attract pollinators.

They also vary in heat, and bees are attending to electric properties of flowers, all sorts of things, but visual and olfactory. Floral signals are the most salient ones that we know that pollinators attend to and they sort of serve different functions So scent typically works to attract bees at longer distances and then visual cues work at closer range To inform bees about the properties of those flowers.

So I Haven’t done any experiments Well, I’ve done a couple of experiments where I’ve manipulated floral color, but in most of my experiments, I’m manipulating properties of the reward themselves, since color is sort of an arbitrary stimulus that informs bees about the quality of the reward, but it’s not necessarily informative on its own.

And so in one particular experiment, what we were interested in was how bees form [00:03:00] expectations about reward quality based on their recent experience and how floral signals can sort of serve as labels. That mediate those expectations. And so we’ve done an experiment where we trained bees to either a blue or a yellow flower that was paired with a high quality reward.

So high, high sucrose concentration nectar, and then we downshifted that reward and either paired that downshifted reward with a new. Flower color or with the previously rewarding flower color, and we looked at how their expectations about reward quality were being mediated by their previous experience with either that blue or yellow flower.

And then we did a follow up experiment where we tested the bounds of these expectations. So we did find that that these expectations were mediated by flower color. That’s not necessarily that surprising that they’re learning that yellow flowers. predict good rewards and same for blue. And if you give them a medium quality reward on a new flower, that’s a new association that they’re forming.

The interesting part of that is that the medium quality reward may be rejected or accepted depending on their previous experience. So a medium [00:04:00] quality reward is not necessarily a medium quality reward. It depends on what you had previously. We then tested the bounds of those expectations to other flower colors.

We did a follow up experiment where we just trained bees to blue flowers, and then we tested them with down shifted rewards across a range of stimuli that ranged from blue to green. And we found that they actually generalized their preferences quite a bit to other flower colors that are similar. And so this may mean that if you are a flower that’s blooming alongside another flower with a similar color, and you don’t have equally good rewards, you may bear the cost of higher expectations.

in a way that’s not beneficial to eliciting visitation. Can we talk a little more about what you found regarding bees expectations? So there’s this really well documented phenomenon that’s been shown. It’s not ubiquitous across taxa, but it’s really common across a lot of different taxa, um, called incident contrast effects.

We actually exhibit this behavior in our everyday lives. But it’s this idea that we assess the quality of a particular option based on our recent experience or a reference with something [00:05:00] similar. And this is mediated through expectations like product labels in humans. So if I give you bad wine out of a good bottle, You may consider it worse than if I gave it out of its original bottle and so we’re finding that here in this study, they’re forming expectations based on the flower color.

And that’s mediating their expectations about the quality of their reward. So if they know that yellow gives a high quality reward, we expect them to go to that flower color. And then if yellow becomes less rewarding, it really disrupts their behavior in a pretty significant way. Why is pollinator cognition important?

Well, I think animal cognition in general is really important to study, but I think pollinator cognition in particular has some really interesting implications and consequences for how we think about plant pollinator interactions. There has been a long history of studies studying the sort of foraging economics in pollinator settings and trying to figure out how bees and other pollinators make decisions and learn about different flowers based on the floral signals and properties of the rewards.

And many of those studies have. [00:06:00] acknowledge some of the limitations in terms of pollinator cognition that bias the ways in which animals make decisions and learn about things. But it seems like it’s really only recently that cognitive limitations and cognitive biases have informed how we understand how plants interact with pollinators and vice versa in a way that I think has some really important implications across a variety of settings.

Where would you like to see the research go in this area? I highlighted a few areas of future research. Obviously, we’re in a rapidly changing world where bees are exposed to a lot of other stressors, and this has really important implications for how bees interact with flowers and how they perceive and learn about floral rewards.

So, the introduction of Insecticides and pesticides obviously has really important implications for how various aspects of pollinator cognition for how pollinators perceive and evaluate and learn about different floral signals and those rewards. We also know things like heat stresses can have really important consequences for pollinator cognition.

[00:07:00] And so we’re just really scratching the surface in that regard right now. And so I think that there’s a lot of work that can be done that’s going to be really interesting in the next few years that comes out of that. Interesting, upsetting, but interesting for my own personal research. Again, I’m really interested in how animals make decisions with multi attribute multi alternative decision tasks.

And so, in these really unfriendly choice environments that pollinators encounter on a regular basis. Sort of which cognitive biases are really prevalent and how does this drive decision making and learning in robust ways that can inform our understanding of this interaction. Bees evaluate the quality of nectar relative to their most recent feeding experience.

Meaning yummy nectar from a certain flower makes it highly likely that the bee will visit similar flowers. Strategic planting may support the crucial pollination services bees provide. Thanks so much to Dr. Claire Hemingway for sharing her work, and thanks to you for listening. Until next time, [00:08:00] plant strategically.