174 - Veronica Wignall - Whacking bees for science: Competitive exclusion between honey bees and bumblebees in the UK

Andony Melathopoulos: [00:00:00] I just snuck in the studio here for a second because I want to announce we have a guest host this week. Everybody loves a guest host and everybody loves Emily Carlson. She's a PhD candidate here in the Department of Horticulture at Oregon State University. Many of you remember, she had this great show that she hosted with Dr. Christina Grozinger. She's going to go across the Atlantic today, and she's got a great interview lined up for you. So let me make myself scarce and get out of the studio and hand things over to Emily Carlson this week on PolliNation.

Emily Carlson: [00:00:27] In any environment with enough flowers, be it a natural area or your garden, or even a crop pollination environment, you're likely to see dozens of species of bees flying from flower to flower, collecting pollen and nectar to provision their nests.

But have you ever wondered how these different species of bee might be interacting with each other? This week on PolliNation, we're taking the podcast all the way to the laboratory of apiculture and social insects, which is based out of the University of Sussex in Brighton, in the Southeastern United Kingdom.

We'll be speaking with Veronic Wignall, a PhD researcher there, who has been exploring some big questions related to insect conservation. How do we improve floral resources for pollinators? And also, how do we investigate resource competition between those pollinators? Are bees and other insects competing for floral rewards. Stay tuned this week on PolliNation for our conversation with Veronica.

Veronica your recent work deals with competition between social and solitary bees. Can you explain a bit more about what exploitive competition is and why it's an important concept for ecologists?

Virginia Wignall: [00:02:01] Yeah, of course. So exploitative competition is also called resource competition, and it's unlike the competition we normally think of where there's like fights over food.  You imagine like a lion and a hyena fighting over some food. Bees and insects are pretty peaceful when it comes to that kind of thing. So they compete indirectly and exploitive competition is a version of competition where shared and finite resource is depleted by one competitor, which means that there's less of it available for the next one.

So if you picture a bee foraging on a flower, it takes the nectar out of the flower, the next bee visiting that flower and finds that there's less nectar there for it to extract. So essentially they're undergoing an indirect form of competition. And that's what my research has been about.

Emily Carlson: [00:02:50] So essentially you're saying that the solitary bees and the social bees might be competing, even though they're not actually fighting. We might not see them, going at each other after this resource, but there's competition taking place that's like kind of more subtle.

Virginia Wignall: [00:03:06] Yeah, exactly. Yeah. Really difficult to spot it happening, but it's happening all the time, which I suppose we'll come on to as we start talking about my experimental methods. But yeah not necessarily just social bees competing with solitary bees, but also bees within the same species competing with each other. Because if, for example, if we take honey bees, if a honey bee is visiting a flower extracting the nectar and pollen, and then the next visitor to that flower is also a honeybee, which is quite likely since they recruit each other to the same flower species.

Yet again, you'll have less resource and it's important for ecologists and also for conservation, because flowers are a limited resource. They produce minute quantities of nectar and pollen and in the UK, at least quite often, there's not that many flowers around at certain times of the year, so you can find there's a situation where there's a shared resource shared amongst lots of foraging taxa that is not super abundant. So you can get some competition, which is probably shaping foraging communities to an extent that we might not realize.

Emily Carlson: [00:04:06] Okay. So that leads perfectly into our next question, which is one of the innovative and interesting things about your work is that you've experimentally manipulated this competition.

So can you explain a little bit more about that and like what you found that was interesting?

Virginia Wignall: [00:04:27] Yeah. I suppose in that as well is the why, so why did we do that there? And that goes back to what I was saying before, which is that you might look at a foraging community of insects and not recognize or not be able to see these combative interactions that are happening because they're indirect, like we were talking about.

So you might see a bumblebee foraging on a patch of lavender and think, "Oh, bumblebee like lavender," and not really think "could there be other bees that would be forging now or other insects that would be forging there potentially if the bumblebee wasn't there." So what we do in our research, in my lab and what I've done follows on from work by Nick Balfour, who I worked with, is we remove those competitors and see what happens.

So we've removed particularly focusing on new social bees since they tend to be quite intense resource uses like honeybees and bumblebees live in colonies. They needed a lot of nectar and pollen. So we did an experimental method we called experimental or manual exclusion. And we physically removed certain bee types from patches of flowers.

And we had control patches of flowers where we didn't remove any bees. And we looked to see if there was any difference. Firstly, in the nectar content of the flowers and secondarily in what types of bees and how many bees or other insects visited those flowers compared to the control patches.

Emily Carlson: [00:05:48] So you have to tell me more about the manual exclusion.

So how did you, how do you keep bees off of flowers? What did you do to prevent them from entering that environment?

Virginia Wignall: [00:06:00] This is always something I really enjoy talking about at conferences and things because we literally tap them all there. Yep. So if you are monitoring a patch of flowers and it's a really labor-intensive form of experiments, so it always have really good team of research assistants. And we're out in the field all day during the foraging days. So we'll be there from eight in the morning, till six in the evening using a bamboo cane.

And if you gently tap a bee foraging on a flower, it flies away. So we'll have a patch for any honeybee approaching that patch, you'll have your eye on it. And as soon as it lands or before it lands, you give it a little tap and it will fly away.

Emily Carlson: [00:06:34] Cool. So you and your team are essentially standing in front of these patches of flowers, like wielding bamboo canes, preventing the bees from landing on it in order to stimulate this exclusion. In order to get the bees to leave the area and be like, "Oh, I don't like that. I don't like being tapped."

Virginia Wignall: [00:06:53] Without trying to affect it too much, so we're trying not to loom over the patch because you don't want to affect anything else that might want to come. Although, having said that never seems to bother bees, right? They never really mind if you're there; they're on a mission. They'll ignore you.

But if you don't need to have those bees that you don't want forging in a certain patch, then it seems like a really good method. It reduces those bees to almost zero. And then we've had really good success with it. It does sound crazy.

I read a paper recently. In the US someone had done a seminar thing, but they'd used a little jet stream where they blew some air at the bees to remove them.

Emily Carlson: [00:07:28] That's awesome. That's something I haven't thought too much about is using either puffs of air or bamboo canes in order to exclude bees from foraging. So I think that's really innovative.

So you mentioned a little bit about what you've found. Can you tell us, can you give a little more detail about that? So looking at these different  setup of the design, if I understand correctly, was you had one patch of flowers where you were excluding bumblebees and one patch of the flowers where you're excluding honeybees and then one patch of flowers where you didn't do anything.

Great. So can you tell us a little bit about what you saw that was different between those patches of flowers?

Virginia Wignall: [00:08:04] Sure. So in this experiment, we were actually looking at how competition varies over the whole foraging season. And so we'd previously shown that this does have an effect. So I'll talk through that first.

So if you on this particular flower where we're using, which was lavender, and there's a long corolla tube, and the nectar is right at the base of the corolla tubes. So right at the base of the flower, and that gives a bee with a longer tongue a competitive advantage. So this comes back to what I was saying before, where if you saw some bumblebees foraging on some lavender, you'd think, "Oh, bumblebees really like lavender." And you might not think, or you might think also, "Oh, honeybees maybe don't like lavender so much."

Cause there's always a lot of honeybees around here. I can see them on the Ivy. I can see them on whatever else, but they're not on this patch of flowers. But actually previous like by Nick showed that if you tap away the bumblebees over a sustained period of time, what happens is that since they're not taking the nectar with their long tongues, the nectar builds up to an extent where the honeybees can forge on those flowers and then can also make an energetic profit.

So it shows this what we call ecological release from competition. So when the dominant competitor, the bumblebees, the long tongue bumblebees, aren't there, it becomes energetically profitable for the honeybee to forage, so it's showed that they would be there if this other combustor wasn't present, basically.

Emily Carlson: [00:09:26] So is it, just to make sure I'm understanding correctly. So is it that basically the nectar in the lavender never has a chance to build up to the point where the honeybee doesn't have to work super hard in order to get it, because it's being constantly drained by the bumblebee.

Virginia Wignall: [00:09:44] So that's the situation with this particular flower and mechanisms  of competition work differently on different flower types, but with this particular one that was the mechanism, the underlying mechanism that we found was going on. Yeah. And it is quite sweet because if you're watching the flowers, you see a bumblebee and they're just like bam flower.

And they're just so quick and efficient extracting the nectar. And if you see a honeybee, it really has to burrow his whole head into the flower to try and get anything out of it. So you can see it happening with your own eyes if you have time to stop and look. But yeah, then, so what we then did is we repeated this experiment with the three patches, like you said, and we did it from May until September.

Each trial we did was three days long or no, sorry, four days long. So we had a good amount of time to see what was going on. And what we wanted to see was are there times of year when competition is particularly strong? And other times of year, where insects could be compensated for, by the fact that competition is less strong.

And this brings us to an idea of per insect resource availability. So you might have plenty of them flowers out there, but you might also have loads of insects, or you might have not many flowers, but not many insects in which case competition is low. Did we have not many flowers, and plenty of insights, there's less food to around and we call that kind of low per insect resource availability.

And what we found was, in every trial when we'd removed those long-tongued bumblebee bumblebees from the flat patch of the flowers, the nectar increased significantly in the flowers. So there was a lot of nectar there. But we found that in earlier summer, and also in the autumn, we weren't seeing an increase in honeybees on the flowers.

So there didn't seem to be any ecological release from competition. It didn't seem like the honey bees needed that nectar. But then in the late summer, so in here in July and August, we found that removing the bumblebees caused this increase in nectar, but it also has the significant increase in honeybee numbers.

So yes, suddenly there were loads of honeybees forging on the farms and you could see it. If you looked at a patch, the bumblebee excluded patch, and it'd be covered in honeybees. So it seemed like there was this this ecological release from competition. The honeybees would be there. They did need the nectar and yeah, we saw that in five of our trials.

Emily Carlson: [00:11:52] So incorporating that seasonal variability is a really interesting aspect to add to this question. You found that this resource was more important to honey bees in the later part of the season. Do you know anything about, what other flowers are in bloom during that time or why maybe this was such a critical period for them?

Virginia Wignall: [00:12:17] So that's a really good question. And it was one of the most interesting things to come out of this research is it's another piece of a jigsaw that we're seeing in the UK, and I'd have to put the caveat in that this was in the South East UK. So it might not necessarily apply to everywhere where we find different flowers in different reaches of the country.

 In this particular region, it seems like July and August is a particularly challenging time for bees. So we also had some research in our lab where we showed that honeybees. We use waggle dance decoding to show that honeybees were foraging a lot further in the summer to collect the resource that they need.

So it adds this element, which shows that there's also a stronger competition for the flowers that are available in the late summer. In the UK we've seen over I guess probably a hundred, 150 years, we've seen a big decrease in the amount of arable weeds that are available for bees and insects.

And that wasn't necessarily recognized until like the mid 19 hundreds. And then suddenly everywhere there's a lot of the changes in agricultural practices to make things more efficient after world war two had meant that basically lots of weeds and flowering hedges and flowering trees are cleared out of the landscape and because most of the flowers that come into bloom in the late summer months, so July and August, is herbaceous flowers rather than trees or shrubs. That means that a lot of the flowers that have been removed from the landscape where those which would have come into bloom in July and August.

So that's potentially a reason why there's a potential scarcity of resource at that time of year. And at the same time, a lot of insects have their peak flight periods at that time of year. So a lot of, not just bees, but hover flies, butterflies will be on the wing in July and August. So there's less food to go around.

Emily Carlson: [00:13:58] So we've got this kind of perfect storm in late summer where you have lots of insects emerging and at the same time, you have potentially historically less flowers than would be present in the landscape during that time. So what, kind of putting all this picture together, what can we learn that would help us better conserve insects in the UK or, in North America?

Virginia Wignall: [00:14:25] Well in the UK definitely. And I guess in North America too, although obviously I know less about it. The message for conservation that I always tell to people is just to plant more flowers, and that's not a simple thing, but it is something that everybody can get involved with, whether it's on your balcony or in a pot, or, at your school or wherever you are, everybody can plant more flowers and all those flowers will add to what's available for insects.

But the particular seasonal variation of it, is useful for policy in terms of when we plant things like agri-environment measures to help bees and farmland, or when we, or the kind of species that we use to plant. And when we plant them to submit, to make sure there's enough, particularly at that time of year.

Emily Carlson: [00:15:05] Got it. So taking that individual action of just planting, what flowers you can. But also trying to, as a society, organize bloom during the periods that scientific research has shown us are the most stressful for pollinators.

Virginia Wignall: [00:15:23] Not just planting, but also allowing flowers to grow. For you, you know how it is, but here we seem to have an obsession with mowing, not just in our gardens, but on road verges and in public green space, there are mowers out all the time.

And actually you could be allowing clover to grow. That would be a really good resource at that time of year, and if we all recognize that there's not only you need to provide more flowers for insects, many of which are struggling, but also particularly in the summer, like everyone likes a nice green lawn, but also we need more flowers. So maybe there's a good balance to reach somewhere.

Emily Carlson: [00:15:52] I think that's a great sentiment. And so we're going to take our first break and we'll be back in just a moment.

So welcome back. Moving right along, I think something that's probably on a lot of our listeners minds right now is that honeybees are native to England, but they are not native to North America.

How do you think that honeybee presence is impacting the native bees of North America? Or what do you think might have been different about this experiment if you had conducted it with lavender in the United States?

Virginia Wignall: [00:16:27] This is probably closer to your research than mine, so maybe you can help me along. But I suppose any introduction of a non-native species has potential to have more of an impact on the native species because they haven't had all those millennia to solve and to adapt and flexibly, create their communities, foraging patterns, so that there's this kind of adaptive partitioning of resources. So there is potential there for honey bees have more of a negative impact, but I want to tread really cautiously because I don't know enough about it.

And it's probably, it is also definitely something that's very difficult to show in research as I'm sure... but there has been some research to show particularly there's a really great, interesting study showing that the amount of resource that the non-native honeybees take out of the environment. So this particular study looks at pollen, and they found that over one month, honeybees pastured on Wildlands, and then they're not being used for that for pollination purposes. And their kind of downtime to get some forage, they can take enough pollen out of the environment, that would feed, that would lead to 33,000 average size progeny of native wild bees. So you can see that honeybees are taking a lot of pollen to their hives which then isn't available for native bees.

So they're  definitely is this potential to have a detrimental impact, but I suppose it comes back to what I was saying before, which is that none of this would be a problem if there was enough flowers around. It's not necessarily the honeybees fault or the beekeepers fault, or anything like that. It's just a situation where we need to make sure all insects are being supported.

Emily Carlson: [00:18:12] I think that's a really interesting point because honeybees obviously are social just like bumblebees. And so they're gonna provision like large brood nest. But a really missing piece of this question seems to be, to me, when is that hitting? Is that hitting during a time when we have a high level of competition, when you know, native bees are really already looking for resources or is that hitting during a time when there's plenty of resources all around? And we could even have more bees in the environment and there would be plenty of flowers to feed them.

And so I think that timing aspect is really something that's interesting that It could be resolved in the future.

Virginia Wignall: [00:18:51] Timing and also location. Are you in a place where there's monoculture agriculture and you aren't necessarily having enough wildflowers around to support insects or are you in a place where there is a lot of natural pasture? So it depends on whereabouts you are as well.

Emily Carlson: [00:19:05] No, that's a great point. Especially because a lot of native bees here in North America, the solitary ones at least, usually have pretty short flight distances. So if you don't have an area where the native bees haven't liked, if they haven't been there historically, then there's nothing to compete with. Because how are they going to get there?

Virginia Wignall: [00:19:27] Yeah. Compared to a honeybee you're flying what, up to 12 kilometers at the time, if it needs to? Yeah.

Emily Carlson: [00:19:33] Yeah. The diversity of pollinators and insects in general is astounding.

Virginia Wignall: [00:19:38] I suppose it's interesting to think about per hive, how much a colony can take out of the environment. So there's that Thomas Seeley study, which showed that one strong honeybee colony over a foraging season takes in about 120 kilograms of pollen. Just to put that into a kind of figure that you can almost imagine 120 kilograms of nectar, and 20 kilograms of pollen, which is just so much in one hive.

Emily Carlson: [00:20:08] Yeah. That's to feed all those hard working insects that are doing all of that agricultural labor. Yeah, I'd be hungry too. I get it. What's next for you? So can you tell us a little bit about where you are in your career and then where you're moving to and what questions about competition or bees in general you're excited to start answering next?

Virginia Wignall: [00:20:31] I guess I'll answer these separately starting with the second bit. So in terms of questions about competition, like with so many other people, I got to the end of my research and just had so many more questions than I did answers. So I'd love to do what I'd done before, but to also look at pollen, for example we chose to focus on nectar, but I'd love to look at pollen and see how that's affecting the whole dynamics of competition.

I'd also love to do more studies on a gradient of floral resource availability. So study competition in a place where you know where you can do a really thorough assessment of the floral resources that are available and choose a kind of gradient, so you can see how that particular factor is affecting the strength of competition, which is really difficult to do.

Like we we're saying before, I'd need a lot of people tapping bees in a field with me which, would be really difficult, but really interesting. I'd love to look at it in urban centers compared to kind of urban suburbs, so there's a lot more flowers and also in rural landscapes a lot of... I think there's a lot of questions to answer.

I think it would be really cool to look at how physical presence affects competition. A bumblebee and a honeybee they're also really big, and is there any effect of their physical presence on the flower that causes other species to potentially be displaced in that way? I've never done any research on that. I think there's a small amount of it, but I think it would be really interesting to somehow work out a way of investigating that as well.

Emily Carlson: [00:21:54] The idea that like a bumblebee is just so massive that it might be like really intimidating to something like a small osmia who just like flies by and is like " Nope. Not even gonna, not even gonna try."

Exactly.

Virginia Wignall: [00:22:06] We've probably seen right, a big kind of fuzzy bumblebee lands on a flower and everything else just leaves. And it's not because of any aggression there. It's just because it's really big. I don't know. Is that something there? I've got no idea. I would love to look at it, but in terms of your question, what's next for me, I'm starting a different chapter.

And I'm starting a new job next week, actually as a climate action researcher. So I'm moving away from pollinators for a bit, but I don't think it's forever, so we'll have to see what happens.

Emily Carlson: [00:22:36] Awesome. Pollinators definitely need questions answered about climate action. That's something that impacts all of us from bumblebees to polar bears.

So definitely still contributing to the cause in that way. Great. Thank you so much. We are going to take our final break and when we come back, we will have a couple fun questions for you to answer.

All right, welcome back. And we are excited to ask Veronica our last couple fun pollinator questions that we always like to ask every guest on PolliNation. So first up, what is a pollinator book recommendation that you have for our listeners?

Virginia Wignall: [00:23:23] Okay. So this is a book that I haven't read yet, but I know it's going to be amazing. I'm really looking forward to it. And I was given it when I finished my PhD. So it's called Pollinators and Pollination and it's by Jeff Ollerton.

Emily Carlson: [00:23:38] That's awesome. What excites you about it?

Virginia Wignall: [00:23:40] I suppose I just, I actually just think the world of professor Ollerton, that he's an amazing researcher. I love what he does. And I'm just really excited to to know more. His research is really interesting and I'm sure it's going to be an amazing book.

Emily Carlson: [00:23:54] That's awesome. Okay. So next up, what is your go-to tool for the kind of work that you do?

Virginia Wignall: [00:24:01] It's going to have to be the bamboo cane.

Emily Carlson: [00:24:08] Alright, give us specifics like thick, thin?

Virginia Wignall: [00:24:11] So it's gotta be quite long and you want a nice kind of grippable texture. The other thing I would say is essential to any kind of research where you're looking at floral rewards, there's micro capillary tubes to look at nectar.  I got really good at selecting the right size for the right flower and, yeah, can't do without those.

Emily Carlson: [00:24:35] Awesome. Okay, so then our last question for you, what is your favorite pollinators species?

Virginia Wignall: [00:24:43] So there's a little bee in the UK, which is our only blue bee; it has a blue metallic sheen, and it excavates its nest in brambles stems. And it's called ceratina cyanea. I always call it the blue bramble bee, and it's not common. I don't think it's massively rare, but when I see it, it's always just an absolute treat to see. I really love it.

Emily Carlson: [00:25:09] That's awesome. Cool. Do you, so you might see this bee in like backyards or more like agricultural places or?

Virginia Wignall: [00:25:18] That takes me to bramble promoting, which is one of my favorite things to do.

I'm sure wild bramble, blackberry plants, they, I guess we would call them underrated. But they're really important resource of pollinators as well as giving you delicious blackberries in the autumn. And bees love to nest in there. So I hope you could find this bee anywhere you find brambles. So the answer to that is don't cut your brambles down, let them flourish, and hopefully you'll have the pleasure of seeing this tiny bee.

Emily Carlson: [00:25:47] Awesome. Thank you so much for joining us today. It's really a treat to hear about your work and to get an international perspective on pollinators and competition. Certainly a treat for us and all of our listeners. So thank you so much.

Virginia Wignall: [00:26:04] Thanks Emily. It's been great.