78 Emily Erickson – Breeding and The Attractiveness of Garden Plants (in English)

Speaker 1: From the Oregon State University Extension Service, this is Pollination, a podcast that tells the stories of researchers, land managers, and concerned citizens making bold strides to improve the health of pollinators.

I'm your host, Dr. Adoni Melopoulos, assistant professor in pollinator health in the Department of Horticulture. December is a great time to be thinking about what to plant in your garden next spring to attract pollinators. But as we know from previous episodes, like episode 34 with Dr. Gale Angolato, it's easy to get quickly overwhelmed by a large list of plants that supposedly are attractive to pollinators. To help us unravel the complexities of plants different plant cultivars and the various pollinators that could visit your garden, I caught up with Emily Erickson, who's in the Department of Entomology at Penn State University. She's really thinking deeply about the connection between different pollinator species, different plants that are grown in gardens, and the effect of breeding, the multiple cultivars of different plants. It's a really fascinating episode that gets at some very basic science questions about pollinators and the plants they visit, but it also has some very helpful tips for you as gardeners who are thinking ahead to what you can plant for next year. Hope you enjoy the episode. Welcome Emily to Pollination. Thank you. I'm happy to be here.

I'm so glad to have you because you know anywhere you go, right? You go to the garden store and it tells you about the plant, this is a bee-friendly plant and it seems so straightforward. But you're doing research that is trying to get at this question of what makes a pollinator plant. So why is this question of whether a plant is a pollinator plant or not complicated?

Speaker 2: Yeah, so my research looks directly at pollinator attraction to ornamental plant varieties, which are kind of an odd group to look at in the world of plant-pollinator interactions, but this was kind of born out of this issue where we see a lot of people buying these ornamental varieties to plant pollinator-friendly gardens and we see a lot of labeling of these plants as pollinator-friendly plants, but there really isn't any standard measure of what makes them a pollinator-friendly plant.

This project started out from the kind of a very applied side and then my advisor and I were sitting one day and she asked me a question that should have been very simple, which is what makes a plant pollinator-friendly seems relatively easy to answer, but that's been something that has now kind of preoccupied my research going forward.

Speaker 1: And that has to do with the fact that

Speaker 2: there really isn't one thing that makes a plant pollinator-friendly, right? Plants play many different roles in a pollinator community. You can be a plant that supports one pollinator type but is really good at supporting those pollinators, or you can be a plant that supports a lot of pollinators. You can be a plant that offers a lot of really good pollen or plant that offers a lot of really good nectar or both. There's a lot of dimensions to this question.

Speaker 1: I guess it gets complicated because when it comes to home and garden plants, there's also this aesthetic quality driving this election for these plants on top of all that. Yes.

Speaker 2: So that's one of the things that makes these plants both a really odd system to study and also a really fascinating system is the fact that they've been through this breeding history where human preference has been the one thing really driving all of these crazy cultivars that we see, right? And so there's been artificial selection on things like flower color and flower shape. In a lot of cases, low pollen production alters the nutritional reward for bees. These are all ways that could alter the utility of these plants to bees either negatively or positively. And there have been studies showing both ends of that spectrum.

Speaker 1: So you could conceivably have one ancestral, let's say, prosanthemums or something that came from one source. But now, in addition to restoration ecology or something, even crop work, there's not as much variation as there is within the Black Eyed Susan's.

Speaker 2: Yeah. I mean, I think, and for the purposes of our work, because also kind of classifying something as an ornamental is kind of a gray area as well. But for the purpose of my work, we really classify it as really anything that has been through horticultural breeding practices and that you could probably buy at a garden center.

And that also includes, you said, Rebecca, that includes, if we call them native ours, right? And so I am now doing a study looking at cultivars of perennial plants. Three of the species I'm looking at are native to North America. But you actually see a lot more variation in these plants, right? Because they've been selected for these many different varieties. So within one species of marigolds that I'm looking at, I have just a very small sample of all the cultivars available on the market. And I have a red and orange, a yellow, a flame cultivar, which is like a breaking red color. OK.

Speaker 1: So bringing it back, so that your supervisor is sort of like, what does come up with, like, what's a pollinator plant? So there's the issue that the plants provide different resources and may attract different pollinator visitors. And I guess the other thing is the pollinator community may vary from place to place. Yeah.

Speaker 2: So that's kind of the new area that we're looking at. So we know that pollinator communities in urban environments, which is really where these plants tend to be the most commonly planted, are going to be composed of different pollinator species, right? So they're going to be mostly generalist pollinators, which are pollinators that are capable of foraging on a lot of different types of plants. They tend to be much more flexible to kind of changes in their food resource availability. Yeah.

And so urban environments are pretty much exclusively generalist pollinators, whereas more classic pollinator habitat areas, these more rural areas are going to be composed of specialized pollinators as well, which really rely on a certain plant species. OK.

Speaker 1: So that makes sense. Because so when you're in you're being a garden area, your one neighbor is planting like this and the next neighbor is planting this and you got to make a living. So clearly anybody who's just like goes to one thing is not going to cut it.

Speaker 2: It pays to be opportunistic in a city. You know, and cities' landscaping practices are kind of wild, right? So in a lot of cities, especially gardens, not so much, but I see on my campus, the minute one thing stops blooming, they'll rip it out and they'll put in a whole new plant.

Speaker 1: Oh, it's true. It is. Yeah.

Speaker 2: And so, you know, gardens a little less so, but there is kind of this constant turnover of plant material and plant species. And especially with these ornamentals, you know, there are new cultivars being introduced to the market all the time and others taken off. That is kind of this constantly changing environment. So you really will have a hard time if you're a bee that relies on a single food source.

Speaker 1: OK. So we've got these issues when it comes to answering this central question that everybody wants. I mean, imagine a nursery wants to know they're going to put their plants out, and probably they've heard honey bees are not the only bees by now starting to get the words getting out. And they're like, well, let's get all the bees. Like they're probably the one idea is like, I want the one flower to rule them all. I want a flower that attracts nine different kinds of pollinators instead of three.

Speaker 2: But there is no one flower to rule them all. No, that's like that's the really cool thing about plant pollinator communities. But also, you know, it's it's not what people want to hear, especially when they're just trying to get this clean like I'm planting this pollinator-friendly plant. But no, I mean, there are so many studies showing that plant-pollinator interactions, these individual species level interactions, you know, this honey bee goes to visit this sunflower that doesn't exist in a vacuum.

It's based on all the other pollinators in the background and all the other plants that are available. And you know, that might change based on, you know, something that seems kind of like a not direct relationship changing thing. But there are all these studies showing that even as the plant community changes, species-level interactions change. And so that means that there is no perfect plant.

Speaker 1: Well, let me get this straight. So what you just said, so somebody might let's say there's a craze for this one kind of flower. And, you know, the pollinator community still, you know, in the ground wintering, and then they come up and then, oh, my God, some some some Oprah showed this new plant.

Speaker 2: Yes, it's like the world has changed. So they would change. They would then their interactions with that complicated landscape may shift and they may yeah, even visit the flowers. But in fact, if you were to track it all, it would be more. Yeah. And so, you know, and this would be a better job for a real network ecologist to talk about, but, you know, there have been so many studies showing that year to year and site to site across gradients, we see species level interactions changing. But, you know, back to your question of, you know, we all want this like one perfect plant. There are certain plants that are better than others. And that could be kind of where we're getting closer to this area of like what makes something a pollinator-friendly plant, right? Like we know a lot of the mint species, especially, you know, I'm looking at agastaki and Nepida right now, we see a lot of things visiting them in a huge abundance. And we see in our landscape that we're looking at these plants, you know, we do see a lot of plants that seem to be more specialized on the mint family. You know, the annuals that we looked at in this study, they're not the best plants for pollinators.

And I'm certainly not saying that if you're trying to restore pollinators or even attract a huge abundance of pollinators to your garden, you should go out and like cover it with marigolds.

Speaker 1: OK, well, you know what? I think before we get too much further, let's take a quick break because what I want to do, I think you set this up really nicely.

I think the kind of questions are set up really nicely. Let's take a break. And then what I want to do is when we come back to sort of been hinting at some of your research, but I'll give you a good chance to sort of like lay it out so we can follow through the logic of some of your findings.

Cool. All right, we're back and I'm anxious to hear a little bit about you and how you've gone about trying to resolve some of these questions. So tell us a little bit about some of your key questions and hypotheses.

Speaker 2: Yeah, so when we started this study, we kind of had a couple main questions of which, you know, endless questions have then

Speaker 1: come off of which seems to be kind of the like perpetuating circle of research. But, you know, we started this study and we wanted to see, you know, if we put these plants

Speaker 2: in a community where we know there are a lot of pollinators and we know there are a lot of plants that the pollinators may like better, do we see visitation at all?

Right? Are they do they have any potential significance for attracting pollinators and offering pollinators resources? And then we were interested in, you know, these cultivars, right?

And so there've been a couple of studies by Garbazov and Ratniks. They've done extensive work on ornamentals and garden plants. However, there have been a couple of studies illustrating cultivar-level variation in pollinator attractiveness. But we were really interested in kind of expanding this study. They looked at that in that study, I believe it was in 2013, over 200 aster varieties. But we were interested in this study and kind of expanding it. We had a range of pollinator types we were hoping to attract. And so we were kind of seeing if we could generalize that pattern.

Speaker 1: Oh, rather than just show there's variation, say, what's the mechanism?

Speaker 2: Yeah, yeah. So that was that was kind of one of those offshoot questions that came from it. Because when we looked at these out in the field, we saw that some plant genera that we looked at really did see a really impressive variation in the relative attractiveness to pollinators, right? So we had some plants that were getting pretty much everything. And then the cultivar, which is going it's the same species, right? It just differs in like a few key traits and gets almost nothing.

Speaker 1: Can you give us an example of something like that?

Speaker 2: So the best example that I saw was the Lobbularia or the speedalism in my study. And, you know, speedalism is in its wild form. It's this kind of low growing Yeah. Very, very sweet to its name, but also like a little, I think it smells a little like rotten smelling of these small white flowers.

And that's a really classic fly flower. But a lot of the elizem that's now on the market, they've been selecting for like pinks and purples. And so, you know, what we were finding is that the white cultivars were attracting a ton of visitors and they were attracting flies and they were attracting bees. Whereas the purple cultivars weren't getting very much at all.

Speaker 1: Interesting. Okay. I get to decide your point.

Speaker 2: But then we see other cultivars like we also looked at Lantana, which attracts mostly butterflies. We saw a lot of Hawk Moms visiting them on our sites, which was really interesting. But, you know, we had all these different varieties of Lantana and there's all these really cool studies showing how, you know, pollinators have co-evolved with Lantana for this like really intricate floral signaling mechanism to show when there's reward present or not. And we saw no difference in cultivars, even though they were all, you know, they differed slightly in color between them in ways that you would predict would probably alter their attractiveness.

Speaker 1: Okay. So you started off looking at the, going across, not just looking at, you know, all the one group of plant, all the variation, but you wanted to get at the mechanism and you did notice kind of contradictory results.

Speaker 2: Some of them, you didn't see something and some of you did. You know, this study is kind of perpetually in two different spheres. One being the kind of more applied is how can we take the results from this study and come up with practical methods for working with the green industry to kind of scientifically evaluate these plants on attractiveness. So it's important to know whether there is cultivar level variation and whether we should take into account that kind of more cultivar level effect. But there's also a lot of really interesting ecological questions that come from this, right? There's been this kind of constant question of how plants and pollinators have co-evolved and how that's led to this incredible diversity of plants. And with this, we can really kind of get at these intricate mechanisms of pollinator learning and pollinator attraction to certain floral traits, a lot of which we're still like, we're really excited about it. We're still kind of trying to work through it right now.

Speaker 1: I guess in wild plant populations, there's variation, but not this much of variation that allows you to really kind of like get stark. Things are brought into relief.

Speaker 2: Yeah, yeah. You know, in wild plants, most of the variation you'll see, of course, you will see within species variations, but you know, the variation is mostly on the species level. But in these cultivars, you have all of these varieties of the same species that have been selected for certain traits and kind of left the same in other traits. You know, marigolds are a good example.

We work with that. Tijidis pechula is one species that we work with, and they're all the same shape, but they differ in color. Right? And so when we take, and this is also, you know, this is important because this is these studies that have looked at how pollinators are attracted to traits have done so in a way of testing one single trait, right? So you have a board, you put a bumblebee in front of a board and you have like blue flowers and red flowers. And you see, does the bumblebee go for the blue dot or the red dot?

Right, right, right. But we know that, you know, flowers are a really complex signal, right? That is full of it has floral chemistry with the scent and the shape and the color and the nectar reward and the polymer board and all of these traits act together to signal an advertisement for pollinators to say like, Hey, come forage on me, hey, come collect my pollen. And this gives us a really, really cool system where we can kind of isolate these single traits in the context of the whole flower, right? So we can kind of keep everything else consistent and then say, Okay, but what if it was red instead of orange? Does that matter?

Speaker 1: Not not many researchers can boast that they've had thousands of independent plant breeders setting up their experimental design.

Speaker 2: Yeah, you could never come up with this kind of like this is such a great I know those kinds of studies where it's so abstracted out of context that it's really you wonder what the results mean, but here you've got the example that you gave with every other features the same except for color. And then you know, is that how important is the color to this signal signaling pollinators?

Speaker 2: It's also a really cool system because these plants have been, you know, through their breeding process, which some of them like these marigolds have been bred for centuries. They have been kind of removed from any sort of co-selection with pollinators, which means that we can kind of look at these plants as if there's no bias of this co-evolved history, right? There may be some, but we almost get to look at these with these mutant novel phenotypes.

Speaker 1: Because their reproduction depends on the market, not on whether they can make seed and it's not that kind of like propagation game.

Speaker 2: Yes, yeah, well, and a lot of them are vegetatively propagated. So that's another cool thing about ornamental seed. That's why I mean, it just keeps going. I'm never graduating. No, but you know, they're like, especially these annuals, they're mostly clonally propagated. So that gives you another cool opportunity to work with like perfect replicates.

Speaker 1: So you've talked about the first thing is looking at visitation with these different characters and sort of, I guess you need to somehow evaluate what the what's the same and what's different. How's that analysis coming? Do you have any kind of preliminary results of what are these key signals?

Speaker 2: So we're actually we're in the works with most of the floral traits stuff. So as I said, we're working on a study with perennials right now. And we did some kind of preliminary stuff with the annuals. But it was when I was a fresh grad student and was still kind of figuring everything out. So hopefully within the next year, I should have some like pretty good data on floral traits.

Speaker 1: What else are you doing to kind of crack this nut? Some of the other things you're doing?

Speaker 2: Yeah, what I'm working on now is testing to see how bees behave to these floral traits in a lab setting, right? So that's a much more controlled space. We have this theory, which makes sense, but we have to prove it is that the floral display, right? So all of the things that we think of when we think of what we like about flowers, right, the color and the scent and the size of the flower, you know, that is not actually meant for us. It's meant to show pollinators that there's food there. And, you know, in most systems, certainly there are exceptions, but that sort of floral advertisement is kind of an honest signal to the presence of reward. But we as humans have kind of taken these flowers and we left behind the reward and then we just picked up the advertisement and we took it where we wanted to go.

And so we're interested in seeing whether that has kind of led to some separation of the floral signaling with the floral nutritional components. So we're now doing tests in the lab to see if we're testing totally naive bumblebees. And if you've ever tried to get bumblebees to behave in any way, it's a nightmare. But, you know, we want to see whether we see the same patterns of these bumblebees that have never seen a flower before, right? They've never tasted the flower. They don't know what reward is there. Do we see the same patterns of visitation as we see in the field with the bumblebees that have been?

Speaker 1: Because they've already gone through the first thing like this thing and given me nothing.

Speaker 2: Right, right. Exactly. And so we're, you know, we're kind of interested in seeing if there is a mismatch with that, which would be a really cool and interesting result. Or whether, you know, these flowers are still honestly signaling a reward, or whether, you know, the pollinators are just able to override these differences and traits and the reward is a strong enough signal.

Speaker 1: Wow, that is so fascinating. And I could just imagine that that also allows you to sort of get a drill down on what the signal is, what are the signaling components, which we would never know when you were just looking at, we always tell our master gardeners here are five bees that you can identify.

And if you pay close attention to your garden, you'll be able to figure out, you know, which bees and which flowers, but in some ways, but you can't, you can't do that outside of this kind of a setting, being able to think about like, oh, they may have tried to go there once. Yeah. Yeah. Well, let's take a quick break. I've got three questions I ask all our guests and looking forward to your answers. All right, great.

Speaker 2: Welcome back. Thank you.

Speaker 1: So the first question is a book. Is there a book that you would like to recommend to our listeners?

Speaker 2: So not not a single book as much as I read a lot of Michael Pollin when I was first getting into kind of thinking about agriculture. That's how I started on this. I never thought I would be way down this road, making bumblebees fly in a tent. You know, that kind of got me thinking about the natural world and about how humans interact with the natural world and our effect. And I think he's a really incredible writer and he writes in a really kind of understandable and straightforward way. Okay.

Speaker 1: Okay. Great. Yeah. He's a great writer and it's really nice to have like a heart. I think what he does really effectively is he kind of has a historical, you know, he'll take a present-day issue, this that or the other, but then he kind of puts it into some kind of historical relief. Yeah. Yeah. Great suggestion. So the next question we have is do you have a go-to tool for this very complicated work?

Speaker 2: You know, one of the things I love about entomology, at least the fieldwork that I do is that most of my tools can be purchased at Walmart. And I think the most valuable tool that I have used, believe it or not, is a five-gallon bucket that first person, the five-gallon bucket.

Speaker 1: Well, so, you know, the origin to any of these hypotheses comes from hours and hours of sitting in a field and looking at these plants and looking at how pollinators are interacting with these plants and kind of just getting really familiar with the natural history of these pollinators.

Speaker 1: And this involves sitting on a bucket.

Speaker 2: Yeah, I sat on a bucket. I sat for the past three summers. I am, I've sat on a five-gallon bucket. I've had a number of really, really patient undergraduate assistants who have also sat on a bucket with me. My advisor here suggested many times that I might upgrade to a more comfortable stool, but I've gotten kind of attached to my bucket.

Speaker 1: I know I don't want to detach you from it, but I actually might, everybody knows I've mentioned this as an example. I have a go-to tool. Okay, it is the strap-on milking stool. It has a little coil at the bottom so you can go right in the mud and it doesn't sink in. And as you walk along, it looks hilarious. You're listening to a little stinger on your butt, but it is really handy.

Speaker 2: Maybe I'll try that next. No, no, I don't want to try it. I just, I just, I still love that little stool. But anyway, okay.

Speaker 1: Next question. Pollinators, are pollinator species that you really love?

Speaker 2: So I am in a B lab. So I am in a way obligated to, you know, have a strong fondness towards bees in general. But you know, I really like surfing flies. They're awesome. You know, and I, I, for really liking them, I really don't know that much about them. But they're just, they're really kind of, I feel like they're the unsung heroes of a lot of pollination systems. They're really interesting. They're really cool looking. They are. Yeah. I'm a big fan of surfed flies. But if I had to pick a favorite bee,

Speaker 1: no, no, you don't have to, but you can. Okay. Yeah, I'll let you, you can do anything you want. Okay. I like the mega chylons. Yeah.

Speaker 2: They've got the nice little hairy bellies and I like the cuckoos. I always get really excited when I see a cuckoo bee visit one of my plants and the E.B . O.S. bees are like really fascinating.

Speaker 1: They all are. And it's always amazing because you know, they seem kind of rare until you come to a nesting bed and then they're everywhere.

Speaker 2: Like, wow, lay them all. That's where they go. Yeah. Well, it's a real pleasure. Thanks for taking the time to bring us up on this fascinating topic. Good luck with your research. Thank you very much.

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