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Thomas K Wood  




Sight and Sound




Rex Cocroft; Treehoppers  

NPR/NGS Radio Expeditions
13 Sep 1999

  • United States
    New Castle County
  • Newark; University of Delaware
  • 39.67917   -75.75222
  • Stereo
    Sampling Rate
  • 48kHz
    Bit Depth
  • 16-bit
    Equipment Note
  • Stereo=1; Dual-Channel Mono

Show: Bug Communication
Log of DAT #:2
Date: 1999

ng = not good
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Absolute Time


0.00.00 -0.01.48 recorded silence

0.01.48 -0.02.18 AC: Hello? TKW: Hello. AC: Hi, Tom Wood? TKW: Yes. AC: Hi. It's Alex Chadwick. TKW: Right. AC: We're calling because we're doing a piece about the work of Rex Cocroft, TKW: right, AC: And I think Andrea Seabrook had talked to you about our interest in insect communication, and treehoppers, and ... You're quite a treehopper man yourself, I guess.

0.02.18 -0.05.04 TKW: Well, that's all I work with .. AC: You're sited repeatedly in Rex's papers. TKW: Yeah, I work with Umbonia crassicomis the species that Rex has done a lot of work with. I guess what the piece is all about. In the early 70s, and so I do know the critter very well. I am not an expert, I can tell you on vibrational communication, but I do know something about treehoppers, yeah AC: Well, we're interested in both.

TKW: Well, I can, let's see, exactly what do you want to know. I think this is a fascinating piece of work, in a lot of ways, the history of vibrational communication actually, in terms of, to put it in a little bit broader context, in the group of insects that Rex is working with, which are membracids, but they're all part of a larger group of homoptera insects that people would know as cicadas and leafhoppers and this sort of thing ... And there was a paper published in 1949 by a Swede, called insect rumors, and it was the first time where, well maybe it's not the first time, anyway he did a lot of work with morphology and this sort of thing, looking for sound producing structures in cicadas and leafhoppers and another group we call Pholgamorpha now. And there was a hint that treehoppers might actually make songs, but there was no definitive data, until actually Rex Cocroft and Randy Hunt at Eastern Indiana University both about the same time, found these courtship signals, and treehoppers in general in a number of different species.

AC: Let me ask you to pause just a second here, would it be okay for us to record some of this for possible use in a TKW: Oh, of course!. ..

0.05.04 -0.05.36 AC: So, let me go ahead TKW: Just so I don't sound too potty in the head. AC: No, you don't sound too potty in the head, I think you sound fine. Tell me, how should we identify you? TKW: Tom Wood, AC: Professor of, Doctor of, TKW: Oh, I'm a professor yeah, us, professor of Entomology, ... just professor is fine. At the University of Delaware. That would get me in big trouble if we used Delaware State.

0.05.36 -0.08.43 AC: You said that this is fascinating work, and it's fascinating to me, as a layman, just to know that these sounds are there, but why is it fascinating to a scientist? TKW: Well, how to do this, quickly, I'm not sure. I worked in the 1970s with Umbonium, and up until about that time, there had been several, well actually there was a paper that was published in 1894 by a woman who was I think it was in Missouri or in Kansas, she was an invalid in a wheelchair, and she published a little paper about, I can't remember exactly the title at this point, about maternal care in treehoppers, and then there was another woman that worked on some things, in British Guiana and she noticed some, she never called it parental care, but I guess maybe she did, but the point is that there were some earlier records early on that maternal care might actually be occurring in this family of insects. But there was a fellow that, his name was Funkhauser, and he was the treehopper authority, and he poo-pooed the whole idea, and then back in the, somehow I just stumbled into it in the 70s, with Umbonia crassicornus down in Florida, and you've got this really interesting alarm behaviors, I mean females will, if a predator comes near a branch the female will fan her wings, and buzz and drive predators off and this sort of thing, and we even had some indications from some work there, that nymphs when they were injured, produced alarm chemicals and the female would respond and drive off a predator. You can see, we did some early tests where we put a lady-bird beetle on a branch next to a female, and a female can actually knock the beetle off the branch. And back in those days, we never dreamed that there would be other kinds of communication going on and when Rex found this business that nymphs and females can actually communicate back and forth, this is really wild, at least for us, cause we, like I say, just the whole idea of even courtship signals, vibrational courtship signals in treehoppers, hadn't been established at that 5, 6 years ago.

0.08.43 -0.11.02 AC: But when you say, it's really wild, I'm trying to figure out, in terms of evolutionary biology, what is it that's really wild about this? TKW: Well, I don't exactly know how to put it. Well there's this whole, there's some hypothesis out there in terms of maternal care. Say whether, just as an example, perhaps. Is maternal care a primitive trait, that, or is it a derived condition. So that becomes interesting, and then the nature of the communication systems in a phylogenetic sense becomes interesting, what's driving the evolution of these critters. I mean, treehoppers are very very fascinating, just my impression was that you were going to go see some critters today, and when you go see them, you've probably seen pictures to, they're fascinating looking animals. And so just the nature of that pronotum and their shape and so on almost requires some attention, or explanation if you will, but it's more than that. I mean in these treehoppers you have a whole array of uh uh for lack of a better word, how they use host plants, the role of host plants in speciation, which, you start talking in those areas you're talking about well, how do mate recognition signals and so on fit in to the speciation process, at one level. Then you have varying levels of the degree which these things react with ant mutualists, whether these are phylogenetic traits and this sort of thing. And it's the whole complex, this is just another dimension if you will, of the uniqueness of these treehoppers -and I don't know if I'm making myself very clear ...

0.11.02 -0.13.25 AC: Well! It could be clearer, what I'm looking for is a really simple, kind of couple of sentences on what the signif -that I could repeat for our audience, that is that, you know NPR audience, they're pretty smart, but phylogenetic might go by them. TKW: Well, genealogy. AC: If you could say in just a couple of sentences TKW: Well I'm not sure I can AC: You probably can't. TKW: All right, let's not use the word phylogenetic. What we're interested in a sense, is a genealogy. Most people know what a genealogy is, don't they? AC: Sure. TKW: And what we're trying to do is develop a genealogy for treehoppers, all right? And I'm working with a lot of, we're using DNA sequences to infer, or try to develop these genealogies. What we want to, once we develop these genealogies, then we want to know, what are the processes that are responsible for the diversity of tree hoppers. And what I was trying to get at was that you look at treehoppers and you have a tremendous amount of world-wide diversity in terms of species richness in different parts of the world you have a whole array of-patterns that are associated with what host plants they use, and so on, and then there's a continuum of behaviors that are related to whether they, how they interact with ant mutualists, and then we have this maternal care. And what we want to know is how this ultimately what we want to know is how these communication systems whether, one kind of communication system is this parent-offspring communication and then we have courtship signals, and we want to know how these processes operate to essentially give us our present-day diversity of tree hoppers.

0.13.25 -0.15.21 AC: In terms of maternal care, have, how rare is that kind of behavior among these insects? TKW: Well, in terms of the treehoppers, as far, among homopterous insects, all right, and this is a small order, or hemipterous insects, among the cicadas, leafhoppers and so on, treehoppers are basically the only ones that have maternal care. Within the treehoppers themselves, parental care is very very widespread. And that's what I was trying to get at, is earlier, is when you see maternal care showing up in a variety of different genealogies if you will, then you have to begin to ask questions, what -why? Are we talking about maternal care being the result of simply dealing with different ecological pressures molding and forming, molding parental care, certainly maternal care does result in high survival, higher survival of offspring and this sort of thing or is it an ancient trait that goes way back in time. Actually treehoppers have the highest incidence of maternal care probably of any hemipterous group, here we're talking about hemiptera and homoptera. I don't think I'm getting across what I need to get across.

0.15.21 -0.17.57 AC: Well, I don't TKW: I mean maternal care is very very widespread in the group, and as a result they require some attention in that sense in terms of study. I'm not sure what you're trying to get me to say ... AC: I guess I'm just TKW: You want some one-liners and I'm not very good at that. AC: No no no no, that's okay, you're doing fine. I'm, you know, I want some one to say, the work that Rex Cocroft is doing is significant because, TKW: Well, it's significant because I think it's umm, my biases are toward the treehoppers, and it's a significant breakthrough in terms of understanding the biology of these treehoppers. In terms of the communication systems, it actually may turn out to be more complicated than communication systems that exist in other kinds of insects. But that's not exactly what you want. AC: No! That's great! I mean that's pretty interesting, don't you? TKW: Well, yeah I'm fascinated with it, urn, maybe I'm just too close to it in many respects because um I'm just well, I'm fascinated, well-My love for the last 36 years have been treehoppers. And I think it's fascinating to see that even though there has been a lot of work done on these things, that you take somebody that has a completely novel perspective they can come in and look at a group, and find something that most of us never dreamed of 30 years ago. And to me that's the beauty of science. You have a body of work that builds up and then someone comes in and takes a slightly different look at it and all of a sudden there are whole new ways avenues that are opening up in terms of how we view life, and to me, that's the fascination of science.

0.17.57 -0.19.07 AC: When you say whole new avenues opening up into the way that we view life, would science view life differently if you learned that treehoppers have this kind of maternal offspring communication that seems to me amazingly complex and it never occurred to me that any insect would do this kind of thing. RC: Well, yeah I mean we knew in the 70s that we had this high instance of maternal care and to expand it to the point, and this is the beauty of Rex's stuff, to the point where they -parents and offspring are actually talking to each other in a sense, well they are talking to each other, they're communicating to each other in a real sense about the offspring are communicating well they're threatened by a predator, and the females can respond back and forth, I think that's terribly exciting.

0.19.07 -0.20.33 AC: Can you think of a good question for me to ask Rex that would be, that would kind of illuminate all this for people? What should I ask him when we're out there listening to treehoppers today? RC: oh boy. You're a tough man! I guess that's your job. Uh, well I think the question is, where does he see it going in the future, in terms of the avenues of work and so on ... I'd do this better over a beer. AC: Well, come on down, Tom! TKW: You buy, I'll be there! It's only an hour and a half drive ... Well, it's actually the comparative stuff, in terms of what -I would ask him questions, how unique is this communication system, is this just unique to Umbonia, or is it.

0.20.33-0.22.26 AC: You know what I think of when I see this, I wonder for me, when Rex explained this to me and showed that he could demonstrate, I mean he can absolutely demonstrate that his insight here is correct, it changes the way that I think about insect. RC: Oh, I see what you mean, yeah. See the problem is that I've just lived too close to them for all of these years, that is the treehoppers -it's the only thing my wife is truly jealous of. It certainly, to most people that aren't aware of these things, to me I can't go by a tree anymore without thinking there's a whole, when you have a lot of treehoppers on a particular tree, they're talking back and forth, you can't hear them at all. All of a sudden it's opening up a new, it gives me a new appreciation for what's going on on a tree. I mean there's a whole lot of sex going on out there. And these things are having courtship signals, they're communicating by signals that are being transmitted through the branches, and then we've got this parental care and now we have offspring-parent communication, there's even a possibility that there might even be communication between nymphs, immature treehoppers, and ants, which provide protection to them. So it's opening up a whole new way of looking at the evolution of mutualism, parent-offspring interactions, at least as far as treehoppers are concerned.

0.22.26 -0.23.22 AC: Maybe a new way of looking at evolution itself? TKW: well, I don't know if it's a new way of looking at evolution, but it certainly is a component that we can put into our evolutionary perspective in terms of trying to understand what are those processes that produce the diversity of life that we've got within this group, diversity of life histories, diversity of shapes and this sort of thing. We haven't even gotten to the point yet, and actually some of the work that Rex has been doing in Binghamton with some of the engineers there, AC: Ron Myles TKW: Yeah, right. Is very very fascinating.

0.23.22 -0.28.23 AC: let me just ask you this, what is is that you and Rex are doing next summer, and maybe Randy Hunt's a part of that too. TKW: Randy Hunt is very much a part of some of this work, because, and they both came on the scene at the same time, I'm not sure what Rex told you, what we're going to be doing next summer ... AC: .. You have a joint project going on ... ? TKW: Well we're trying to put one together, yeah, and this is getting at the role of, all right, in part what I think Rex is alluding to is that for 30 years I've been working on the role of host-plant shifts, that is when an insect changes it's host -shifts to a novel host whether that initiates genetic divergence that would lead to speciation. Okay? And basically the model that we're using is a sympatric speciation model which does not require geographic isolation, and about 5, 6 years ago, after 30 years we had a set of hypotheses that explain appears to explain speciation in a group of north temperate treehoppers, known as Incanopa, but, it's like science -you spend a long time developing data to generate a hypothesis, then about 5 or 6 years ago, I thought well jeez, if everything that I've been talking about for the last 30 years is occurring, we ought to be able to set up a long-term experiment to actually empirically test the hypothesis, so what we did was set up some experimental host-shifts, where we took treehoppers and shifted them onto novel host plants, to assess whether we would get divergence on these new host plants. And the idea then is next year to go in and see whether we have any divergence in the courtship signals, mating-courtship signals in these treehoppers. And that's what I think he's talking about. Because the whole issue is, what comes first -is it divergence in a sense, selection imposed by a host plant for host adapted genotypes, that is, does the host plant impose the selection ... AC: On the insect, or does the insect begin to look for a new host plant? TKW: because a difference mate-recognition signals, and so this experiment is set up in a sense that, and we have data that you know, a new host plant does impose high mortality and this sort of thing, and then, are we getting, one of the measures if you will is we're going to get diversions has got to be somewhere along the line, diversions in courtship signals.

AC: all right, Tom, thank you

TKW: It's a 30 year experiment.

AC: 30 year experiment ... all right Tom

TKW: You didn't get what you wanted did you?

AC: Yeah we did, but we don't want much

TKW: That's not true

AC: Next time you come to Washington call me up, and we'll get a beer.

AC and TKW chat about beer.

0.28.23 END OF TAPE

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