Floral Foes: How Non-Native Bees Impact Native Ecosystems (Ep. 36)

What challenges do native bee populations face in the wake of non-native bee introductions? And what could be the long-term implications for plant reproduction and diversity? Our guest Dr. Maureen Page shares valuable insights into conservation strategies aimed at protecting essential pollinators and the ecosystems they support. We also discuss future research in this field, identifying key questions and areas that need further investigation to safeguard native bees and their associated plant species.

Dr. Maureen Page is currently a postdoctoral researcher at Cornell University. She completed her PhD in Entomology at UC Davis where she studied the impact of honey bee introductions on plant-pollinator mutualisms. You can read more about the study we discussed, Honey bee introductions displace native bees and decrease pollination of a native wildflower, here.

Good to know

Why are native bees often better pollinators than honey bees? Because they’ve co-evolved with native plants. Native bees’ unique body sizes, shapes, and behaviors make them ideal partners for specific flowers, ensuring better pollen transfer.

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.

When I tell people I have a podcast about bees, the assumption is typically that I’m a beekeeper, I love honey, or I have some other connection with the honeybee. Regular listeners know they won’t learn a lot about honeybees at The Bee’s Knees. I specifically choose to talk about and share my love of native bees, not only because of their critical importance to biodiversity, but also because of their overlooked status.

Today, we’re talking about a complex topic that can also be controversial, honey bees and their impacts on native bees. What are the consequences for native bees when a non native species is [00:01:00] introduced into an ecosystem? Helping us get an informed look at the situation is Dr. Maureen Page, a postdoctoral researcher at Cornell University.

Her study found increasing evidence that honeybees compete with native bees for shared pollen and nectar resources. This is called competitive displacement, in which honeybees remove pollen and nectar resources from flowers, so there is less available for native bees to collect and consume. In a worst case scenario, this could lead to reduced survival and reproduction of native bee species.

But there is more to it than that. How does honeybee competition impact native plant pollination? And, are honey bees and native bees equally good pollinators? Let’s find out. Thank you, Maureen, for being with us today. In your study, you highlighted the indirect effects of honeybee introductions on native bees and plant pollination.

Can you talk a bit about the unique roles that native bees play [00:02:00] in ecosystem health and biodiversity that differentiate them from honeybees? Absolutely. It’s a great question. Well, to start right off the bat, it’s important for everyone to know that honeybees, the bees that we commonly see in the media, these honeybees were brought over by European colonists for beekeeping and for agricultural pollination and they’re economically very important and useful in a lot of different ways, but they’re not native to the Americas.

So When we’re talking about native bees in North America, we have over 4, 000 species of native bees, and they vary a lot in their behaviors, their color, their size, their hairiness, where they caught and carry pollen on their body, as well as their nesting habitat. And this diversity of behaviors is part of what makes native bees so important because.

Some bees will be better pollinators of certain plants, and so having a lot of different native [00:03:00] species in a given ecosystem means that there are bees who are evolutionarily well adapted to pollinate a wide diversity of different native plants. And just to give you some examples, some native bees, like bumblebees, they’re big and hairy.

That means they can carry a lot of pollen on their bodies, which makes them important pollinators. Some plants have evolved really unique pollen dispersing mechanisms, such that they need bees to be just the right size and visit them in a very specialized manner. Native bees also tend to move more in between genetically different plants, so moving farther distances, whereas honeybees tend to move within flowers on the same plant.

And by moving between different far apart plants, what native bees are doing is they’re also delivering more genetically diverse pollen, which is particularly important for plants that either can’t [00:04:00] self pollinate or have genetic incompatibility mechanisms that prevent inbreeding. So, for example, for camas, which is the flower that we were studying in the Sierra, this plant benefits from receiving outcross pollen from different plants, genetically different plants.

And so what we found was that in meadows where we introduced honey bees and therefore saw declines in the native bee populations and native bee visits. These plants received plenty of pollen, but they set much fewer seed compared to plants in meadows that had more native bees and fewer honeybees. And we think that what’s going on here is that the native bees essentially are delivering better, more diverse pollen compared to the honeybees.

And that’s why we see fewer seeds but the same amount of pollen. And we saw that in this system, but there’s good evidence to show that this is [00:05:00] occurring across a lot of different systems. Essentially, honeybees are pretty good at delivering self pollen, but not as good at delivering genetically diverse pollen from plants that are spaced further apart.

 Talking about the camas that you studied in this study, are there any traits or behaviors in native bees that you believe contributed to their higher pollination effectiveness here? Yes, definitely. So in the Sierra, we saw over a hundred species of native bees. And so really, really high bee diversity.

And some of these bees were just more effective than the honeybees. We had bumblebees, which were big and hairy. That helped a lot. But some of the big reasons would be, first of all, the honeybees in our system often displayed a behavior that we call nectar robbing. Where essentially they drink and remove nectar from behind the petals of the plant without [00:06:00] contacting the reproductive structures.

Uh, the anthers, which are the male part of the plant, and the stigma, which is the female part of the plant. So, they’re making the plant less attractive because they’re removing nectar. But they’re not pollinating the plant and by making the plant less attractive, they’re also making it such that native bees are less likely to visit.

And then, as I mentioned before, we also observed that the native bees tended to move in between different plants, whereas the honeybees moved more within the same plant. And again, that’s one of the reasons why the native bees were able to deliver better pollen and the plants that receive native bee visits set higher seed.

So, in this study, you also found that the non native bee introductions can indirectly decrease the pollination by native bees. Do we know how this reduced pollination from the native bees affects plant reproduction and diversity in the long [00:07:00] term? Yeah, that’s a really great question. We definitely need more data, but based on data from other studies and my own knowledge, I I would expect the result or the effect rather to be negative, especially when we’re thinking about maintaining diverse populations, because like I said earlier, bees vary in their effectiveness, their behaviors, their color, their size, as well as their preferences of what plants they like to visit.

And so you really need diverse bees to have diverse plants because not all bees will be good pollinators of all plants or will even visit all plants. And our study found that honeybees competitively displaced native bees. And if those native bee populations declined such that, for example, some species became locally extinct, if we’re left essentially with a population with lower diversity or lowered populations of the native bee [00:08:00] species.

 It might be that essentially the honeybees are able to fill in for the lost native bees and pollinate some of the plants that they’ve competitively displaced, but there’s going to be other species that they just can’t replace those native bees, right? So yeah, the big takeaway really here is that preserving bee biodiversity is super important to maintain plant diversity because Even if honeybees are not negatively impacting all bees, even if it’s just some bees that are negatively impacted, we don’t want to lose some bees at all, right?

We want to keep all the bees. And so that’s why these introductions have the potential to negatively impact ecosystems as a whole by impacting plants like camas, but also potentially other plants that are better pollinated by native bees. So what conservation strategies do you recommend for protecting native bee populations and the ecosystems they support?[00:09:00]

Yes, super, super important. Well, based on my study, which was conducted in meadows around the Tahoe National Forest, the biggest recommendation, at least from a policy perspective, would be to continue current policies of not allowing honeybees in these landscapes. In national parks and forests or natural reserves and other lands set aside specifically for conservation.

A number of federal and state agencies are reviewing these policies and considering allowing honeybees in these landscapes. And while it’s a complicated process and it’s important to acknowledge that, you know, they have to listen to multiple stakeholders, they have to listen to the beekeepers and growers and not just folks like me.

What I would say is that from a conservation perspective, there’s really no benefit of adding honeybees, which again are non native to these landscapes and only risks to [00:10:00] native bees and native plant populations. Outside of that context, there’s also a lot we can do in urban and residential settings like planting diverse flowers.

And this is really great because it supports both honeybees and native bees. And realistically, if we’re going to tell beekeepers, okay, you know, you can’t put your honeybees in those landscapes because they’re set aside for conservation, we need to find other ways to support honeybees and native bees because of their importance as agricultural pollinators.

So, one of the kind of closing comments in your study was to see a more thorough understanding of these indirect effects of species introductions. What are some of the key questions or areas of research you believe should be investigated further to protect the native bees and just as important their associated plant species?

Yeah, absolutely. I suppose my answer touches on something we talked [00:11:00] about a little bit earlier, which is that it’d be good to know more about the long term impacts of these honeybee introductions or really the introduction of any non native species into a system. So for example, in our system, we saw that when we introduced honeybees, there were decreased visits to camas in meadows.

And most likely this was a mix of different things, partially that native bees were still around in the meadows, but they were just visiting different plant species. They may have also been spatially moving to different meadows where honeybees weren’t to escape competition. But we also worked in a couple of meadows where beekeepers come back year after year after year.

And in those meadows, There could also be some demographic changes that are occurring whereby, like I talked about earlier, right, honeybee competition has the potential to negatively impact [00:12:00] native bee populations to reduce the number of native bees as well as the diversity of native bees. And so. We still need to do some research, kind of untangling what’s occurring in this system.

Is it really just behavior shifts, but the native bees are still around? Or in cases where honeybees are brought back to meadows year after year, or even stay in the same meadow for a long period of time, what are these long term demographic consequences for the native bees? And how might that impact

plant pollination? Why do you do what you do? Why bees? Yeah, it’s a great question. It’s both an easy and a hard question. Well, I chose to work with bees mainly by way of my love of flowers. So I started just being really interested in Flowers and ecology in general, and because of my interest in flowering plants, I [00:13:00] became very interested in bees and their importance as pollinators in both agriculture, but also in natural systems.

And since I’ve found that studying bees is deeply rewarding, Because bees are super diverse. They’re really cute and they’re interesting. And also because it’s great to work with a community of researchers, but also community members, you know, outside of academia, outside of science that all care really deeply about bees and about conservation.

And yeah, it’s just a great community to be a part of. Like Maureen said, there are many facets to the honeybee versus native bee dynamic. There are ways we can support the economic importance of honeybees, while also preserving the critical biodiversity importance of native bees. And remember, it’s not just about bee diversity alone.

Bee diversity is critical for maintaining plant diversity, which supports a functioning ecosystem. [00:14:00] I hope this discussion has shed some light on this tough topic, and you feel better informed about the honeybee situation And why we mustn’t neglect our native bees. Thanks as always for listening. Please share The Bee’s Knees with your friends.

Together we can make a difference. Until next time, keep learning.