Buzzworthy Bites: A Deep Dive into the Nutritional Habits of Bees (Ep.31)

When we nourish bees, we nurture biodiversity. But the complex nutritional requirements of bees are not fully researched or understood. In this episode, we take a foodie journey to understand what fuels these tiny pollinators and discover a world beyond simple nectar and pollen. Dr. Sara Leonhardt is trying to understand the dietary requirements of diverse bee species and how environmental changes and chemical stressors impact bee nutrition.

We also look at existing pollinator seed mixes for gardeners and farmers. Sara emphasizes the need to incorporate a knowledge of bees’ nutritional needs into the selection of plant species and highlights the importance of fostering diversity in plantings to support the varying requirements of different bee species.

Sara is a professor in plant insect interactions at the Technical University of Munich in Germany. From the rainforests of Borneo to research labs in Bavaria, Sara’s dedication to understanding and conserving bees exemplifies a blend of scientific curiosity and environmental stewardship.

Good to know

Sara mentioned her PhD work with stingless bees and resin. More than 30% of bee species depend on non-floral resources, like resin. Solitary bees often use resin to build their nests. They also use resin as protection against some predators and microbes.

Transcript

[00:00:00] Welcome to The Bee’s Knees. I’m your host, Jacy Meyer. The Bee’s Knees is 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.

Thanks for being here.

Human nutrition is a complex and diverse field that encompasses a wide range of nutrients essential for growth, development, and overall health. We know what we should eat to be healthy. But the nutritional requirements for bees are just as complex and go way beyond simple nectar and pollen.

Unfortunately, there are quite a few knowledge gaps in what bees actually need to thrive. Joining us to fill some of those gaps is Dr. Sara Leonhardt, [00:01:00] a professor in plant insect interactions at the Technical University of Munich in Germany. Thanks for being here, Sara. Let’s start with the basics. Bees need both pollen and nectar.

Can you explain the difference and what each one offers to bees? Basically, like differentiating between adult bees and the babies, the bee larvae, it’s primarily a sugar solution. So it depends a bit on the plant species, but it can contain a lot of sugar or not so much sugar. So it provides the energy for both adults and larvae, but also mostly for adults.

So many, it depends a bit on the species. There are some species where the adults also consume pollen, but in most cases, it’s really the main food of adults. So they need this sugar solution to keep flying, to keep going, to keep foraging. Whereas for the larvae, because they’re still growing, like first they start as an egg and so that you actually provide nutrients that they need to grow, like proteins, lipids, all the minerals to build up the tissue that’s coming from the [00:02:00] pollen.

So the bees really need pollen for the larvae. Larvae need it as the main food source and that’s what they Yeah, what they need for their development and for their fitness. So when you do a nutritional analysis of pollen, what are you looking for? I have a dream. I want to have the full picture of pollen, which is at the moment really hard to do.

Because pollen is super complex. I sort of can picture it. Well, nectar is easy. Nectar is, as I said, just a solution. It is mostly sugar and a bit of amino acids and some other stuff. Still complicated, but From the bees perspective, it’s really mostly sugar solution, whereas pollen contains everything. It contains the nutrients, like amino acids, which are the building blocks for proteins.

It contains all the lipids, which are fatty acids, but also sterols, which are quite important. Bees need sterols to build up tissue. It also contains the minerals. And that’s a funny thing. What we always forget is that most [00:03:00] plants don’t produce pollen as a resource for bees, but it’s basically their own gamete.

They need it to reproduce themselves. So in order to protect pollen from things that want to eat it, including bees, they also add a whole, Diversity of very toxic compounds. They’re thought to be toxic. It’s the so called bland secondary metabolites, and that’s just a very weird name for describing a lot of different compounds, including things like alkaloids and phenolics, and maybe you know alkaloids from, so there’s some alkaloids which we use for medicine.

It’s like to they tend to be like in high doses, they would be super toxic and they could kill us, but in low doses they can be used for medicine. So alkaloids are quite an interesting group of chemical compounds and that’s all in pollen. Like there’s like pretty much everything in there and it’s always what I want to stress.

So it’s not some not only like a protein as we often see, but it’s just this complexity of compounds. And so if I could, I would analyze it all. That’s pretty much impossible. [00:04:00] So at the moment what we can do in my lab is we mostly analyze sterols, fatty acids and amino acids because we do know they are the most important components for larval growth.

Uh, I do have colleagues who can also Analyze minerals. So in collaborations, try to get the minerals as well, like, um, potassium, uh, sodium, all of those things. And then we have, uh, a really great collaboration with Kew Gardens and they can actually do the plants like in a metabolite. So they, they have a way of screening them all.

Let’s get these thousands of compounds. So if I could, all of this in my lab would be great, but at the moment I’m working with colleagues to really get the full picture of foreign chemistry. Do you have an opinion on existing pollinator seed mixes? Do they do enough or are we better choosing bee friendly food sources ourselves?

That’s a really difficult question. First of all, I would say that, uh, there’s a lot of work and research which has gone into coming up with these seed mixtures [00:05:00] and the bee part or the pollinator part is just one part of the story. Like, the other thing that we need to consider is like, if you, plant these seed mixtures, not all of the plants grow immediately.

Some of them only grow later, which is why they normally contain up to 40 species or even more. And depending on the soil that you’re at, you may not never get all of those species. They also need to be adapted to The soil conditions, the slope, the budget that a farmer has or someone else has in order just to buy these things.

So I think this is way more complicated than just focusing on the bees. And what I can say is that from the bees perspective, I think most people select plants based on how many different pollinators or how many different bees are visiting these plants. They’re hardly paying attention to whether they’re used for nectar collection or pollen collection.

And there’s definitely. Pretty much no knowledge about the nutritional needs of bees and the nutritional profiles of these plants that has gone [00:06:00] into coming up with the seed mixtures, so that is entirely lacking at the moment. And I think we could improve some of these seed mixtures if we incorporated this knowledge about the nutritional needs of bees and

what they actually use these plants for, and that’s not done at the moment, but if you just go out yourself and put them together, I still would say, um, it’s probably not a good idea because there’s so many other aspects to consider, and you may end up with just one plant flowering in your garden if you do your own selection, and Also, the information on nutritional profiles is hardly available, so I think it still makes more sense to, like, of science and the seed producers working together, maybe producing some more new seed mixtures that then people can use.

Are there any common flowers or shrubs that offer quality pollen? Any popular flowers that don’t? That’s another difficult question. So here comes, here come all the knowledge gaps. The problem is, as I said before, like we don’t really know what is a high quality flower because [00:07:00] the original idea was it just needs to have high protein and then it’s fine.

Now we know that there’s a lot of plants that have a high protein content. They may also have like high fatty acid content and then they may not be so good. Uh, it also depends on the ratio of nutrients. So I would say there are like, and then it depends on the species too. Cause you, you may, as I said, we just have honey bee and um, and we don’t know anything about, for example, Halictidae, most of the Megachilidae, uh, like many of those specialized bees.

I just have no idea what their nutrition requirements are. So I can’t really say if a plant is good for this bee or for that bee or in general, I think we could roughly say if we have, um, a really broad nutritional diversity. So plants that offer both like some species, which offer high protein content, others, which offer higher fatty content, fatty acid content, maybe some plants that also offer, um, good sterol composition.

So you [00:08:00] really, I think you really need the diversity of plants in terms, not just in colors and, uh, families, but also in terms of nutrition and that would help. But as I said, like we, we are still lacking most of the knowledge to really come up with like good predictions about what plants are good and which ones are not so good.

And I think that’s something we can say in general, like if there’s just one kind of pollen available, it is very likely not to meet the nutritional requirements of bees. So if they still can have a diversity of plants, they will be fine. They will select what they need. But if they are confined to one or few, two, three plant species in our very empty landscapes, that’s when they are struggling.

How is climate change affecting the nutritional quality of flowers? That’s another question where we have very little knowledge. There’s some data showing that if you have like increased droughts, which is one of the main things that would change or which according to focus would change with [00:09:00] climate change, that is definitely affecting plants and it’s also affecting the resources.

So higher droughts or more drought situations means less nectar. Also, sometimes in nectar, sometimes highly concentrated, but it depends on the plant species we found. And that was something that really like got me thinking and also shocked me was we did some experiments, just one plant species. So in this case, we used centaurea nigra.

Yeah, one of those corn flowers and we exposed it to a heat wave, which is also something at least for Like the forecast for Bavaria, which is where I am is that we will have more extreme droughts, more extreme heat waves And so what we did is we said, okay Let’s just play a heat wave in 50 years from now and see what happens and we found is that it’s not just a So we’re not, we haven’t looked at the quality, so not at the nutritional quality yet, but just the overall amount of pollen was significantly reduced.[00:10:00]

And I’m talking about a heat wave, which is just the same length and maybe two to two and a half degrees warmer than what we see at the moment. So this is not extreme and already you see this really, really intensive effect on amount. And I mean, even if the pollen quality is the same, it still means there’s less protein for bees and that clearly has an effect.

So I assume that there’s a very strong effect of climate change. Because there’s a strong effect of climate change on flowers. Many of them are suffering and that is definitely also affecting the resources that they provide. So there will be subsequent effects on pollinators which we may not even think of at the moment.

So when it comes to bee nutrition research, what are you most interested in exploring? I have two big questions that I really, really love to answer while I’m still able to do that. One is like really understanding the nutritional requirements of different species and going away from just the bombus and apis and like looking at other [00:11:00] solitary bees, also specialized bees.

And it’s time consuming because We need to know what the bees need in order to provide it. That’s one question. The other one is exactly what you have started to ask. Like, what, what’s happening now? Like, we have all these, these stresses. We’ve all these changes, climate change, land use change. We are destroying our nature in so many different ways, which is affecting flowers and then in turn affecting the bees.

And I believe a lot of those impacts are driven by the chemistry or by the changes in chemistry. Also, like, think that we add chemicals, like we add antibiotics, we add pesticides. Add, like, all these things to the soil, which are then, like, degraded into different products and end up in plants again, including pollen nectar.

So we’re not just changing the chemistry by the stressors, we’re also adding things that will end up in a totally different chemical profile of resources. And I really would like to understand how that’s affecting bees. So yeah, that is the second big question that I’m interested in, which I would love to be able to solve within the next [00:12:00] couple of years.

Why do you do what you do? Why bees? Okay. So, um, now, I have to take you a little bit away from the German side. So I started working with bees in Borneo and I was still like part of doing my diploma studies in biology. And I really, really wanted to go to the rainforest. I didn’t think about bees at that time, but I was lucky to do a really cool project on stingless bees.

Stingless bees, they are one of the most important bionids in the tropical ecosystem. So they are like super species rich and they’re super cool critters. They can be small, can be big, they have different colors, they have different behaviors. So it’s a really cool group. And I got to know them when I was in Borneo for the first time.

And I fell in love. Like I really fell in love with those bees. And I also did my PhD on Stingless bees. Bit of a different question. I tried to understand like the use of resin, which is another resource we didn’t even talk about today, [00:13:00] but they use it a lot and that yeah, basically got me trapped, so I got stuck with this resin and bees and I’ve been working on bees ever since.

because I think there are so most of all, I think they’re just super exciting animals. And then of course, like they’re also important. So it makes sense to work on them because we need to conserve bees and to make sure that we also conserve the pollinators, which are pollinating our food. So there’s also, uh, yeah, society relation or important part of these critters that I also appreciate.

But yes, the major reason is it’s just this pure fascination and me being a Childlike. It’s the good thing about science. You can still be a child and ask very funny questions and stupid questions and good questions. Try to answer them. And I have many questions about bees, and that’s why I love to work with them.

Thanks so much to Sara for this nourishing conversation. The chemistry behind bee nutrition is complex, and so much is still unknown. Our rapidly changing [00:14:00] environment means it’s critically important that we deepen our understanding of bee nutrition. The typical bee stressors we’re familiar with pesticides, land use change, the climate crisis are all going to affect whether bees are able to consume a healthy diet

or not. Diversity, diversity, is something we’re always stressing, and here’s another excellent reason for planting a wide variety of flowers, shrubs, and trees in your garden. Thanks for planting, and thanks for listening. I’m glad you were here. Don’t forget to visit the website, thebeesknees. website, and join the hive to receive our twice a month newsletter.

Until next time, be healthy.