Revisiting Duffy & Hay 2000

In a paper published in Ecological Monographs in 2000, Emmett Duffy and Mark Hay demonstrated, using outdoor mesocosm experiments and feeding assays, strong impacts of both fish and amphipods on a benthic community, but found the effects of amphipods were stronger when normalized for biomass. This study was particularly important because, at a time when the ecology of amphipods was still little known, the findings suggested an important role for this group of organisms in benthic community organisation. Sixteen years after the paper was published, I spoke to Emmett Duffy about his interest in this topic, memories of fieldwork and what we have learnt since about the role of amphipods in benthic community organisation.

Citation: Duffy, J. E., & Hay, M. E. (2000). Strong impacts of grazing amphipods on the organization of a benthic community. Ecological Monographs, 70(2), 237-263.

Date of interview: 6 October 2016 (via Skype)

Hari Sridhar: What was your motivation to do the work that was presented in this paper, the experiments presented in this paper? By looking at your publication profile, I came to know that, you’d already, at this point, done lots of work on the system. This is the system you worked on for your PhD too. So, I wanted to know, what was the motivation for these specific experiments in relation to the work you had done before this?

Emmett Duffy: When I first was exploring graduate schools, I talked to Mark Hay, who became my major professor, about possible ideas. And he was studying plant herbivore ecology and suggested that one thing we really don’t know anything about is what these small invertebrates like amphipods are doing in marine ecosystems. His background was plant herbivore ecology. And, you know, lots of people were studying grazing fishes and sea urchins, but nobody really knew much about what amphipods were doing. My interest was in invertebrate zoology and ecology, and so I said, yeah, that sounds like something interesting to study. So, when I came to North Carolina, I began going out in the field and collecting these animals and playing with them in the lab to see what they were doing. And we decided that they look like they are having a significant effect. So, ultimately, the way to determine what they’re doing in the system was an experiment. But it’s difficult to do experiments with these animals because they’re very small and very mobile. And so it was only a few years into it that we came up with a way to test that. So, I actually did this experiment after I had finished my PhD, and came back to North Carolina for a while. And then it took a while to get published, which is why it’s so much later than the others. But, basically, the motivation was to try to understand whether these small, inconspicuous invertebrates might be having a big effect on community organization that nobody had recognized before.

HS: Stepping back a bit, you said, you said you had an interest invertebrate zoology. How did you get interested in marine biology? Was marine biology a conscious choice you made when you were getting into graduate school?

ED: Yeah, that’s an interesting question. When I was a kid I just loved animals. I was very interested in animals and read books and looked for snakes and turtles and so on, all around. And so I knew early on that I wanted to study animals and be a biologist. I didn’t know what that meant, of course, but I knew that that’s what I wanted to do. For most of my early life, I was really more interested in the terrestrial systems around me. So I did a lot of backpacking and so on. And I think where I first became interested in marine animals was on a trip to California. My cousins lived in the LA area, and we used to drive out there – I grew up in Washington, DC area – and we used to drive out there and I can remember going to the beach one day, and there were some tide pools that had lots of interesting creatures – anemones and sea urchins and snails and algae. And I just remember thinking this was a wonderland, because I’d never seen anything like it. And I think that was the beginning of it.

HS: You say that, though you’d been working on the system for a long time, experiments were impossible till much later. What changed to make experiments possible? Was it some new method or technology or was it just, you know, that you were able to learn more about the system and figure out ways to do experiments?

ED: Yeah, I think it was the latter. We did these in a mesocosm tank. We later figured out how to do some of this in the field, in the ZEN (Zostera Experimental Network), but at that time, it was difficult to do. Well, let me let me step back. The typical approach in marine systems to exclude animals is caging and these guys are too small to cage. So we ended up using this insecticide. And that method had been used before. So we sort of knew about it from an early time, but, I think it was, as you say, we kind of learned about what was possible and learned about the natural history of these animals, and came to the conclusion that they probably were important in this system, and so decided to design an intensive experiment to test that.

HS: You use an insecticide called ‘Sevin’. How did you pick this insecticide? Was it something that people had used earlier for similar experiments?

ED: Yes, it had been used before. In particular, we knew that our colleague, Bob Carpenter, had used it in a paper he published, I think, in 1986 from the Caribbean. But, we also knew that Sevin was used for many years in the Pacific Northwest of North America to clear burrowing shrimp out of oyster beds. They actually dumped this stuff on oyster beds from airplanes. And so the thought was that even though it’s an insecticide it’s relatively mild. Its effects are primarily on arthropods – so crustaceans and insects – and have very little effect, supposedly, on any other animals. So, this was the main motivation for us. Once we figured that out, we decided we would be able to remove the amphipods without hurting anybody else.

HS: The experiments seemed to have involved many different components. Could you give us a sense of how you did these experiments? Did you have people to help you? What was your daily routine like when you were doing these experiments?

ED: Yeah, that’s a good question. I think this is the beauty of being a postdoc, as you may know soon, I hope. During your graduate studies, you have all kinds of classes and exams and so on. But in a postdoctoral position, generally speaking, your responsibility is just to do research. And for me, I had come back to the same place where I did my PhD, so everything was relatively easy. I didn’t have to adapt to a new place, I knew the flora and fauna, and I knew my colleague – my advisor – very well. So this was what I did for probably a year or two, all day, every day, more or less. We certainly had help from some of the other people in the lab, in terms of setting the experiment up, collecting the initial seaweeds to put into it and, and occasionally doing the censuses. This has been a long time now – 1992 – so I don’t remember all the details, but my memory is that, most of that work was done by me after it was set up, in terms of sorting the samples and taking the censuses periodically. But we did have helpers from the lab that would come when we had, you know, kind of a big push to do.

HS: From where did you get the seaweed and fish used in this experiment?

ED: The laboratory where I did the experiment is right near the water. It’s the University of North Carolina’s Marine Lab. Most of these organisms live very close by. There’s a rock jetty nearby the lab that has an abundant growth of seaweeds and it attracts fishes and all kinds of animals. So we just collected them from the field there and brought them in and attempted to start the experiment with relative abundances of seaweeds that were similar to what you would find in the field.

HS: Did Mark Hay get involved in doing the experiments, or was his role mostly supervisory?

ED: He was involved in some phases of the field work, although, mostly, that was my responsibility. I will say that the initial idea, or at least part of it, came from him, because it was part of a grant that he had gotten. He wanted to do something to do with experimental manipulation of the amphipods, and basically brought me back to North Carolina to run the experiment. And then I made some modifications to the design myself. He helped with the writing in terms of editing…we wrote it together – Mark and I always had a very collaborative writing relationship. Most of the actual field and lab work and the analyses were mine.

HS: Do you remember how long the writing took and when and where you did most of the writing?

ED: Um, gosh. I’m trying to remember this. It took a long time to get this paper out. My memory is that I had, of course, started analyzing the data immediately after the experiment. The experiment was done in 1992, I believe. Sorry, no, it was 1991 – 25 years ago; well!  Immediately afterwards I began analyzing the data, but a couple of things happened. I went off to another postdoc and got involved in some other research. Honestly, I think what happened was that it was such a big data set, and also, the statistics of it very tricky. It was a split plot design, which nobody knew how to analyze in those days; at least none of my acquaintances knew. This was of course before the internet, so I couldn’t just go on and, you know, find somebody with an R script that knew how to do it. So that stuck me back a bit. I had lots of conversations with people about how to analyze the data. A few told me, oh no, you can’t do it. I said, well, you know, of course we can do it; we just have to figure out a way. That was part of it. And, of course, sorting the samples took a long time, because we had samples full of amphipods and seaweeds to process at the end. And the other part of it was that, you know, I left North Carolina pretty shortly after the experiment was over. And so that was moving to a new place and getting settled and doing a new project and so on. So it took a really long time.

HS: Had Mark Hay moved to Georgia by the time the paper was published?

ED: That’s right. He probably left right about the time that the paper was published. I think he moved to Georgia Tech. in 2000. I believe that’s right; possibly 99

HS: The manuscript was received by the journal in 98. Just before you submitted it, did you and Mark get together, again, to, sort of, finalize it? Or was it done, mostly, over the phone and email?

ED: Let’s see…98, 99, 2000. Yeah, my memory is that it was done mostly over email. Gosh, at this stage, it might have even been by mail. I don’t even know if you could send an attachment back in those days. But, in other words, remotely; primarily remotely. At that time, I had been a faculty member at Virginia Institute of Marine Science for about four years. I don’t remember that we got together in person about this.

HS: Did the paper itself have a relatively smooth ride through peer review? Was Ecological Monographs the first place you submitted to?

ED: Yeah, that’s interesting. I submitted it to Ecology. The editor was Bruce Menge. Bruce was very keen on making sure that all of the ANOVA tables were actually published. To his credit, I think, he wanted to make sure that it was very clear how the statistics were done, and that somebody could, in principle, sort through them and, kind of, redo it themselves. We didn’t include the raw data; nobody did that in those days. Bruce wanted to make sure that all the ANOVA tables were in there, and there were a very large number of ANOVA tables. In those days there was no such thing as supplementary online material. And so, because the ANOVA tables added several pages to the manuscript, it bumped it up over the 15 page limit for an Ecology article; strangely enough, that’s essentially the distinction between Ecology and Ecological Monographs.

HS: Do you remember if the reviewer comments were easy to deal with?

ED: You know, honestly, I really don’t remember what the reviews were like on this. Those reviews are probably up in my attic somewhere. I checked to see if I still have them, but I couldn’t locate them, before your call. I don’t remember, actually. You know what, now that I think about it, Bob Paine might have reviewed this. I’m not sure if he identified himself or not. But, you know, my memory is that, in general, there was appropriate sort of scepticism and due diligence on the methods, but I wouldn’t say that we had a hard time with it.

HS: I also wanted to go over the names in the Acknowledgments to get a sense of how these people helped. Could we do that?

ED: Yes, of course.  So, let me go down here. Okay, so let’s see…Buffy Turner, Quaker Kappel and Bob Tempe for help with the experiments. Let’s see, Buffy was a technician, and the other two were students in Mark’s lab at the time. So those were my fellow graduate students. As I mentioned before, I had some help getting the things set up, and when we had a big push to harvest everything at the end, and we needed everybody on board. So those were some of the people that helped with that. This was kind of the way it worked in Mark’s lab, and the way I tried to do it in my own lab as well later, is that when anyone in the lab had to do something that really needed a lot of people, we would all pitch in and just go around and everyone would help with everyone else. So those were the people that helped with the experiments. Greg Skilleter was a postdoc in the lab of Pete Peterson, at the time. I had long talks with him about how to analyze the data. And, yes, now we’re getting to your question about the reviewers; that must be who these people are – Eric Berlow, Jim Estes, Bruce Menge, Bob Paine and Richard Taylor. Richard Taylor was I believe, a postdoc in Mark’s lab after I left, but he helped us with comments on the manuscript. As I mentioned, already, I’m pretty sure Bruce Menge was the editor of this manuscript for Ecological Monographs. And I guess that Eric Berlow and Bob Paine were reviewers, and maybe Jim Estes too. So, it appears that they identified themselves. I didn’t actually remember that, although, now that I think about it, I do remember that Eric Berlow was involved. I’m not sure if Jim Estes was a reviewer or we had sent the manuscript to him for comments.

HS: You say you used the digitizing program ‘NIH image’ you measure the areas of fronds. Tell us more about this program.

ED: Well, that was, more or less, my familiarity. I gather that it’s used to do things like look at the areas of cells or disease tissue or whatever, in microscope slides or other images in biomedicine; having come out of NIH. That would be my guess. This is similar to what I think now is called ImageJ, the freeware for image analysis. I think it was a precursor of that back in the day. I have no idea how I found it back then, presumably someone else around the lab was using it.

HS: Today, do you also use ImageJ for such analysis?

ED: Well, actually, I haven’t really had much need for doing these kind of digitizing activities in my recent research. We’ve used ImageJ in the past for doing some measurements in our taxonomic work, for example. We use Coral Point Count and the like for scoring benthic photoquadrats.

HS: At the time when the paper was published, do you remember if it attracted a lot of attention among colleagues and within academia, in general?

ED: Yeah, that’s a good question. I mean, it’s a different world now than it was then. You didn’t have the relatively real time citation metrics and so on, that are available now. It was not obvious to me that it had a big impact at the time. It has been cited quite a few times, which I’m very proud of. Back then when we didn’t have access to today’s online tools, we had to use other means of, sort of, evaluating its impact. And I do remember that I presented it at a benthic ecology meeting and a very senior colleague, who I respected a lot, told me that it was it was a really great story; that I really was excited about. And the fact that that it went for review to people like Bob Paine and Jim Estes and Bruce Menge, who were all, sort of, heroes of mine as a graduate student, meant a lot. First of all, that they would take the call, so to speak, that they would bother to review the thing. And, secondly, that, you know, they gave it a positive review. So that was kind of my metric of the interest in it. And it has had good citations I know now.

HS: Do you have a sense of what it mostly gets cited for?

ED: That’s a very interesting question, actually. I don’t know. I should go back and look at some of those citations. I mean, I think, mostly, it’s cited as showing that these small, inconspicuous animals can have a significant impact on the organization of communities. That, to me, was the major message of it, you know, if you look on a per biomass basis, small quantities of grazing crustaceans have a pretty big impact. There are always issues with how far you can extrapolate from mesocosm studies like this, but certainly, I think, within those constraints, it’s pretty clear that these guys are potentially important players.

HS: Did this paper have any kind of direct impact on your career?

ED: Yeah, it certainly did. In terms of jobs, it’s a little bit hard to say, kind of what it is that gets you a job in the end. Ecological Monographs is certainly one of the premier journals in the field, so I was very proud to have a paper there. And, because it’s a monograph, it’s inherently a very substantive piece of work; it’s not a least publishable unit. So, I was very proud of that. I think, others also interpret it as a significant contribution. The other thing that I would say about it is, to this day, it is one of very few studies that have really experimentally manipulated amphipods, which might sound like a sort of an obscure topic, but, the fact is that, amphipods are really a major group of animals in almost all kinds of aquatic environments. And up until this point, we had, actually, very little idea of what they were doing. The way I sometimes think about it is, you know, imagine oceanographers not knowing what planktonic copepods were doing; it’s somewhat similar. You asked how it influenced my career. I did a lot of experimental ecology as a graduate student, both in my own work and a lot of collaborative work with Mark, but this was really the first time that I had done a classical – I’ll say,  field experiment, even though it was in a mesocosm – but, in other words, a classical experiment looking at community organisation with different sorts of treatments over time. I learned a lot from that and I was very proud of the work. And it also, I think, really influenced my later development when I arrived at VIMS and started working on seagrass systems, for the simple reason that that was, basically, the only thing around that was similar to what I’d studied earlier. You know, my background had been in plant-herbivore interactions, and those were really the only plants around when I arrived in the Chesapeake. So when I started that work, I, similarly, built a mesocosm system and continued this work, in a sense, in focusing on how these small animals influence benthic community organization.

HS: In the paper you mention that there hasn’t been much experiment work on amphipods. Would you say that’s still the case?

ED: I should qualify it a little bit. There are many more people working on these small invertebrates in marine systems today. I think there’s a much better recognition of the fact that they are important herbivores. And, there is more experimental work, but I would say that most of it is either in the mesocosm or lab systems, or field experiments looking at amphipods as a response variable rather than manipulating their abundance. I think it’s fair to say that there has been relatively little field experimentation on these guys. I hope I’m not, sort of,  short-changing somebody’s papers that I’ve missed, but I think that’s still true.

HS: Today, it’s 16 years since the paper was published and 25 years since the work was done. Would you say that the main conclusions from this paper still hold true more or less?  I’d like to read a section from the paper: “Our results demonstrate that grazing amphipods can produce impacts on benthic community organization that are comparable or greater in magnitude, but markedly different in kind, to the widely appreciated impacts of fishes. Could you reflect on that statement and Figure 12 where you caricature this through four figures?

ED: I do think that’s still true. I mean, one might argue a little bit about the relative impacts. What I would say, in relation to that, is that’s about potential impacts. So, in other words, in many systems the potential impacts or interaction strengths of amphipods are not realized because they’re kept at low abundances by predators. But there are some systems where you have actually pretty high abundances of these animals. And so, I guess how would say it is that, when released from predation, they can reach very large numbers, and the combination of those large numbers and high impact per unit biomass means that they can potentially cause big changes in the organization of communities. I think, even though there have been relatively few additional experiments that have really looked at that carefully, everything we know about their natural history and their ecology is consistent with that. Fishes and larger macro invertebrates, generally, have stronger impacts because they tend to have higher biomass in most systems. But, you know, it’s relevant in terms of global change, broadly speaking, because, these guys can respond very rapidly to change. They have short generation times, and they often do respond, for example, to reduction of fishes in systems. So, I think that they are likely to be important parts of trophic cascades that happen widely in, for example, overfished systems, but that are still not very widely recognized.

HS: You also say you believe that “the isolated effects of amphipods are a realistic estimate of their potential community impact where fish predation is negligible, whereas a finding of strong amphipod impacts in the presence of fish is suggestive but needs re-examination under more realistic amphipod densities.”Has that happened? Have there been subsequent experiments by your group or others where they’ve been able to maintain densities at levels comparable to what is seen naturally?

ED: There have been relatively few experiments that have done that. And so, I think that, generally speaking, still holds. As I mentioned, most of the experimental work that’s been done in this general area has continued to use microcosms, and there are, a number of, possibly, confounding issues with that. One is that the amphipods tend to reach a lot higher abundances in microcosms than they do in the field. Part of that may be that they can’t emigrate and move around as much, predation pressure is probably lower, and another major thing, I think, is that the walls of the tanks tend to grow a lot of algae and so the productivity and food availability are much higher for them, typically, in these mesocosms, which also, of course, are in very shallow water up on land. So there’s lots of light and lots of algal productivity. So, the answer is, I think that question really has not been addressed very well, since.

HS: Do we now know more about factors that control amphipod densities in the field?

ED: Hmm, that’s a good question. I’m trying to think back on this. Well, let me let me say it this way: there have been a number of, sort of, classical caging studies in marine systems showing that amphipods, isopods, these kind of small invertebrates, tend to increase a lot in abundance when they are protected from predation. So, I think it’s fair to say that there is pretty good widespread evidence of strong top-down control on these animals. This is a complicated question, because the driving forces vary among scales, for one thing. You see the same thing, for example, in trying to figure out the importance of bottom-up and top-down factors in pelagic systems. So, for example, on a regional scale, if you look across regions, you’ll generally find a positive correlation between algal productivity and invertebrate productivity and fish productivity, for example, suggesting that they’re strong bottom-up control. And, you know, at some level that has to be true, right -if you don’t have light to grow plants and nutrients, you’re not going to get any animals. But at more local scales, where you have variation among habitats, or among patches within habitats, you can see negative correlations between trophic levels, which experiments have shown are consistent with top down control, at that scale.

HS: In the end, you make the general point that we don’t know so much about the community impacts of these smaller, inconspicuous animals, and that they deserve more attention. Would you say that, in the last 15 years, there’s been more than more attention on these groups?

ED: Yes, I think that’s definitely changed. I mean, when I started my PhD, which was in 1985, there was essentially nobody working on amphipods, in terms of their community interactions in marine systems. There were taxonomists, of course, and there were people doing, you know, feeding studies and biological studies, physiology and so on. And, to be fair, there was a lot of interest in the role of small crustaceans in more ecosystem contexts, as conduits of productivity flowing up to fishes and migrating birds and so on. But there was very little community ecology going on. In fact, the major exception to that was Graham Edgar‘s work in Australia, who, I think, to this day, has produced the strongest body of research on the role of these small invertebrates in ecosystem dynamics, particularly, working in both kelp beds and sea grass systems. But apart from Graham and I, there was very little else going on for quite a few years. And that’s different now. I mean, there have been a lot of people in the last 10 years or more that have been studying amphipods. I think they have recognized that they have a lot of very useful characteristics as model organisms, as well as being important in natural systems. And, you know, a lot of them came out of Mark Hay’s lab, and have some connection to Mark Hay – either his children or his grandchildren, so to speak. So, you know, this was a big theme in my lab at VIMS, a number of Mark’s students worked on amphipods, Jay Stachowicz who went to UC Davis and a number of his students have worked on them. But there have also been others. There has been some great work in the Baltic region coming out of Ulrich Sommer’s lab in Germany, as well as number of my colleagues in Sweden– first Suzy Baden and Per Moksnes, and now quite a few others. So, there’s really been, sort of, a renaissance of amphipod ecology in the last couple of decades.

HS: I you were to, in a sense, redo these experiments today, would you change anything? In the paper, you talk about the challenges in designing these experiments, and analyzing the data. I wanted to know whether you would do anything different in terms of the design or technology used or in the way you analyze the data.

ED: Yeah. As is often the case, experimental design is influenced as much by what’s possible logistically as it is by what you’d like to do. And that was the reason for the split plot design here, is that we could only apply insecticide to an entire tank. And so we had the fish on one side and not the other. And, you know, statistics have just been completely revolutionized since that time. So, we would have much more sophisticated ways of analyzing those data now, through, linear mixed models and Bayesian types of approaches that would have many fewer restrictive assumptions than what we were using. So, in that sense, I think, we would analyze it in a different way. I mean, I think, fortunately, the results are straightforward enough that you probably would get the same answer no matter how you look at it. In terms of the design, I think the basic question about the relative impacts of the fishes and amphipods is kind of the first step. I mean, what I might do next would be to try to relate that more specifically to some other kinds of environmental change drivers. It would be very interesting to see how changing temperature and acidification influenced those, but that’s essentially just adding another factor to a factorial design. And, in fact, Mary O’Connor, who was a graduate student later, just happened to be also at University of North Carolina, did some really nice work along those lines, looking at how warmer temperatures influenced the plant-herbivore interaction, and put it into a theoretical context too.  

After I did that experiment, I spent much of the next 10 years or so, looking at how not just the presence and absence of these animals, but their diversity influenced the development of the communities and sea grass beds. That was, kind of, a major new direction that I took after that.

HS: Will the experimental setup be the same today?

ED: I think it would be quite similar. I mean, what you want in a situation like that is a system that works and is as simple as possible, in terms of the work required in maintaining it, which was constant. I mean, basically, every day  – weekends and everything – the first thing I did in the morning and the last thing I did before I left was to check on the system and make sure that the seawater hadn’t gone off, that pump hadn’t broken, there were not clogs in the line and so on. So, that’s a lot of maintenance. But, it’s a very simple system. The dump buckets were a brilliant idea that was actually developed by Walter Adey at the Smithsonian. A lot of the technology was very simple, and I don’t know that I would do it any differently today. In fact, the system that I built at VIMS was based on that design with the dump buckets in the tanks. And a student of mine, Amanda Spivak, who set up her own lab at the Woods Hole Oceanographic Institution a few years ago, essentially built the same system there. I mean, it was much nicer, it was in a greenhouse  – she had more money to do it; let’s put it that way – but the basic design was very similar.

HS: Is the experimental setup in North Carolina still being used?

ED: I think it is. I have not been down there for a few years, but it was being used last time I was there. I think,  oftentimes, it’s used kind of more as a holding facility for animals, but I know that a number of other experiments have been done in those tanks.

HS: Who’s in-charge of the setup now?

ED: You know, I’m not sure has ownership, so to speak, of those tanks at this stage. I don’t know who controls them actually.

HS: In the paper you provide a table of abundances of different species at a place called Radio Island Jetty. Have you been back to the site after the study? Do you have a sense of whether it’s changed a lot since you worked there?

ED: Yeah, that’s a great question. I have been back there, I think only once underwater, and that was only maybe four or five years after I left. So I don’t know, but some of my colleagues worked there after me, some of my more junior colleagues that I know, and my memory is that the community has changed in the direction that one might expect from climate warming. You get more tropical species now. It was always sort of a transitionary community; it was very different in the winter than it was in the summer. The jetty in North Carolina got very cold in the wintertime, into quite chilly temperatures, and it was very much tropical in the summer, and we would see tropical Caribbean fish, you know, sort of post larval small fish on the jetty in late summer that just disappeared later. Offshore, some of the tropical Caribbean species live on hard grounds off shore. My memory is that people had told me that some of the more tropical algae that you see in the late summer there had begun to expand and stick around longer. But it’s been quite some time since I’ve been there.

HS: Have you ever read the paper after it was published?

ED: I have. I occasionally do that. Before we talked today,  I went through it quickly. So, I reread the abstract and I looked at all the figures again, just to remind myself what I’d done. But, unfortunately, I didn’t have the opportunity to, actually read, the whole thing in detail, which I would like to do. I enjoy doing that sometimes.

HS: In what context have you gone back to reading parts of it? Was it because you in responding to someone’s query about it or was it when you were writing something else?

ED: Yeah, both of those things. Occasionally, I’ll feel that I need to be up to speed on what I did in order to be able to answer questions, you know, not necessarily about this paper, but about what’s known about these animals. And, certainly, on occasions where I’m writing a review paper or writing additional papers about this general field, where I need to remind myself what has been done. So, I have had an occasion to read it a few times.

HS: When you compare this paper to the papers you write today, do you notice any striking differences in the way you write?

ED: Well, the big thing is that it’s a lot longer than most papers that I write today. But that’s less me than how the field has changed. There’s very little place for this kind of paper anymore. When I was a graduate student, Ecology was the premier journal in the field, as, I think, for the most part, it still is, although there are a lot more journals now, and some of the others have come in to prominence. But at that time, Ecology papers were very detailed, had a fair amount of natural history, and they were really meaty papers. In some ways, I feel that it was a kinder and gentler time, so to speak, in that you had more time to read in those days. I’d be interested to hear your take on this, actually, but I feel that it’s much more of a mash up society today – and this is true of me as it is, I think, of students – we have everything at our fingertips, everything is hyperlinked, it’s very rare to sit down and remove all distractions and actually read through a paper carefully and have a chance to think about it. I think it’s fair to say that’s the way we used to do it. When I was a student, you would sit in the library or sit at home with your journal or wherever, and read the thing, whereas now much of it as done online, you’re checking the abstract to see if it has something you need, you’re flashing through the figures. So, it was a different time. And I think the writing style, to some extent, reflects that. I’m not sure people read Ecological Monographs papers anymore. I don’t know. I think there’s been a big change in, you know, not just scientists or students, but in the population of the world, in general, in our attention span.

I have very fond memories, you know, from graduate school days, and even in the early days of my faculty job, of going to the library. And, at that time the library was, an intellectual centre. You would look and say, oh, what journals came out this week, and you would go look at them, and flip through these different papers that, you know, much of it is serendipity, and which you wouldn’t see in the modern era. So part of it was finding those papers, but the other part of it was, I feel that there was more acceptance in those days of the appropriateness of just sitting down and reading for a few hours. My impression is, certainly in my own case, it’s very difficult to do that. But I think even among graduate students, it’s not the way it once was.

HS: Would you count this paper as one of your favourites among all the papers you’ve published?

ED: I would, actually, for a couple of the reasons that we’ve talked about. I mean, this is probably the most in-depth work that I’ve done on any particular study -looking at the field abundances, a pretty substantial factorial experiment, feeding assays, and really trying to bring it all together. I tend to think that for an ecologist, you know, field experiments are kind of the gold standard of how you learn about how the world works. And this was the closest I could come to a field experiment, given the limitations of working with these animals. And plus it was very enjoyable to do the experiment. As I said, I was a postdoc – I won’t say I had nothing else to do; of course, we always have other things to do – but this was really my primary activity for over a year. And so, I was able to really, really immerse myself in it. As I say, I’m proud of the way that it worked out, and, I think, it’s stood the test of time. So, it is one of my favourite papers.

HS: What would you say to a student who is about to read this paper today? You What should he or she takeaway from, you know, this paper published 16 years ago, of work done 25 years ago? Would you add any caveats they should keep in mind when reading this paper?

ED: Well, I would say, take a deep breath and go to a quiet place and be prepared to sit there for a while; because it’s a long paper. You know, I’m not sure how to say this. exactly. I would not give them a caveat. My feeling is that it’s important for students to just go into this without prejudice, and see what they get out of it. Because, the more guidance one gives to a student doing something like that- it can be very helpful of course – inevitably, you’re constraining their viewpoint in a certain way. And, so much in science depends on creativity and individuality and seeing things in a new way. Beginning students are our best hope, so to speak, in terms of advancing the field because, they’re always seeing things in a new way. And so I wouldn’t say anything – with this paper and other papers – except to do your best to read them in a situation where you can really think about them. And there are a lot more papers than there were when I was in school, and so, it’s a big job just deciding what to read. When you do read, I think you get a lot more out of them from that deep reading. And you can’t do that with every paper, so there is some job involved in that selection process.