*Featured image photo credit: Laura Bizzarri

In this episode, Laura Bizzarri (PhD candidate, Garcia-Robledo lab) chats with us about her new paper, Bizzarri et al. 2022: ‘DNA Barcoding Reveals Generalization and Host Overlap in Hummingbird Flower Mites: Implications for the Mating Rendezvous Hypothesis.’ We talk about her meticulous fieldwork studying these tiny hummingbirds transporting even tinier flower mites, the ecology that might explain the lack of specialization among mite species, and how the time is ripe to revisit classic hypotheses in our field with modern genetic tools. Listen to our conversation and then read Laura’s full paper here!

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Craving more context? Email Laura at laura.bizzarri@uconn.edu.

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<figure class="wp-block-image size-large"><figcaption>La Selva flowers, credit Laura Bizzarri</figcaption></figure>



<figure class="wp-block-image size-large"><figcaption>A mite under the mite-croscope, credit Laura Bizzarri</figcaption></figure>
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NATURALIST SELECTIONS IS AN INTERVIEW SERIES PRODUCED BY THE AMERICAN SOCIETY OF NATURALISTS GRADUATE COUNCIL. WE SHOWCASE GRADUATE STUDENT AND POSTDOC AUTHORED WORK IN THE AMERICAN NATURALIST, A PREMIER PEER-REVIEWED JOURNAL FOR ECOLOGY, EVOLUTION, AND ANIMAL BEHAVIOR RESEARCH. CATCH UP ON EXCITING NEW PAPERS YOU MAY HAVE MISSED FROM THE JOURNAL, AND MEET SOME TRULY BRILLIANT EARLY CAREER NATURALISTS!

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Credits

Featured Guest: Laura Bizzarri, University of Connecticut, US

Host, Editor, Producer: Sarah McPeek, University of Virginia, US

Original Music: Daniel Nondorf, University of Virginia, US

Transcript:

You’re listening to Naturalist Selections, a science podcast featuring graduate student and postdoc-authored work in The American Naturalist, produced by the American Society of Naturalists Graduate Council. I’m grad council rep Sarah McPeek and today I’m talking with graduate student first-author Laura Bizzarri! Laura is currently a PhD candidate with Carlos Garcia-Robledo at the University of Connecticut, US. Her April Am Nat paper is called: “DNA Barcoding Reveals Generalization and Host Overlap in Hummingbird Flower Mites: Implications for the Mating Rendezvous Hypothesis.” Hummingbird flower mites are tiny nectar-feeding arachnids that live in the flowers of tropical hummingbird-pollinated plant species. They hitch rides on the faces of unwitting hummingbirds to disperse among flowers. For a long time, researchers hypothesized that mite species would evolve to each specialize on a single flower species because specialization would maximize their chances of encountering a mate via hummingbird taxi among flowers of the same species. Laura set out to test whether hummingbird flower mites truly follow this ‘mating rendezvous hypothesis’ at La Selva Biological Station in Costa Rica. She used DNA barcoding analyses to examine the diversity of the mite communities found on 14 flower species. Her phylogenetic work reveals 18 distinct mite species and a much more complicated story than previous morphology-based species identifications could resolve. While a couple of the mites can be classified as flower specialists, most of the species she identified are generalists that feed on multiple flower species. This suggests that other ecological pressures such as resource competition may mediate mite flower-use more than sexual selection. In our conversation, Laura tells me about the fascinating natural history that may contribute to flower mite generalization at La Selva and reflects on the importance of revisiting classic hypotheses in our field with the tools of 21^st century science.

Sarah

As I was reading, my imagination was really running wild about what your field work must be like in La Selva. So can you tell me a little bit about just what it’s like to be out there in the field working on these flowers, watching these hummingbirds?

Laura

Yeah, definitely. It can be hectic. So a lot of it depends on the weather and that sort of thing. Luckily, the flowers are sort of always there, and it’s easy to just go out. So I would go out, try and find the plant species that I was looking for, and then just collect as many open flowers as I could and then bring them back to the labs. So La Selva was really nice because they have labs both, like, ambient labs and actual research facilities, and then just dissect the flowers under the microscope to extract all of the mites. It’s really hard, really, when you’re in the field, like, in the jungle, to actually start counting mites, especially because they start running out and they’re really fast and it’s a mess. It’s a lot easier to come than when they’re in ethanol under the microscope.

Sarah

That makes a lot of sense. You can actually see them in the field, but it’s just really hard to keep track of. I also have mites on the plants that I work on, and they move incredibly fast.

Laura

Yeah. Especially when they sense any motions like you simply touching the flower. They can probably sense that already. And so I don’t know if it’s like a defense mechanism. They start running around out of the flower. And so the idea is to just go in, pick off the flower as fast as possible, and put it in a tube with ethanol for preservation.

Sarah

Makes sense. Have you ever seen the mites on hummingbirds themselves? Because that’s how they get transported between flowers?

Laura

I actually have at least one video. So part of my research, I also recorded interaction between hummingbirds and their host plants using cameras. Right and in one of the videos, we could actually see mites running up and down the beak of the hummingbird.

Sarah

Oh, my gosh.

Laura

So that’s the closest I’ve gotten to see it happen in its natural setting. Right. But then for another part of the project, I also collected mites from the hummingbird beaks. So I was mist netting hummingbird, and so there obviously, when I collected the mites I could see them.

Sarah

So do they kind of stay right in the facial area so that they’re primed and ready to jump back off onto the next flower?

Laura

Yeah so what they do is that they will climb up the beak and then they usually hide in the nares, the nose of the Hummingbird. Right.

Sarah

That makes me itchy.

Laura

Yes. Then they just hide in there and then wait around basically until the hummingbird gets to a flower that somehow they might think is the right flower to get off.

Sarah

Do you know if the hummingbirds are aware that the mites are there, or are they so small that they don’t even feel them?

Laura

That’s a really good question. And I wonder that a lot in general, we say they’re not parasitic mites, so they don’t harm the hummingbirds. But I have wondered if it is itchy for the hummingbird to have tiny critters just running around in the noses. Yeah.

Sarah

It’s a really exciting and unique system. I’m also curious about why you decided to test the mating rendezvous theory in your work? What got you really interested in examining this old idea that we thought about the system for a long time using these new genetic tools that we now have?

Laura

So it was a bit of a combination of multiple things. So I think my first main goal was to just survey, like, mite species, Hummingbird mite species at this location at La Selva to at least have an idea of how many species there are, what host plants they use, what hummingbirds they use, and start figuring out the interactions. And then obviously doing all the background research, I read a lot about this Mating Rendezvous hypothesis, and so kind of went hand in hand with trying to survey the mites because then at that point, I had the data to actually test this hypothesis to see if this really high degree of specialization is actually what is happening. And then the DNA bar coding component came in, so that is something that my advisor had experience with in the research that he had done previously. And then it’s something that we started talking about. And I thought it was a really cool tool and also fairly feasible and accessible. I thought it would be a really good way of conducting this survey and potentially testing this Mating Rendezvous hypothesis.

Sarah

When you were initially going into that investigation, were you expecting to support the hypothesis