In a paper published in Ecological Monographs in 1990, Kirk Winemiller described and compared four aquatic food webs from Costa Rica and Venezuela, and related their properties to properties of the biotic communities and the physical environment. Winemiller’s study was one of the first to put food web theory to test using well-sampled empirical food web datasets. Twenty-seven years after the paper was published, I asked Kirk Winemiller about his interest in food webs, memories of field work and what we have learnt since about this topic.
Citation: Winemiller, K. O. (1990). Spatial and temporal variation in tropical fish trophic networks. Ecological monographs, 60(3), 331-367.
Date of interview: Questions sent by email on 18th December 2017; responses received by email on 8th March 2018.
Hari Sridhar: I would like to start by asking you about the origins of this paper and the study it describes. Correct me if I’m wrong, but this work seems to have formed a part of your PhD dissertation. Could you tell us the motivations for this particular study in the larger context of your PhD? In 1990, you wrote another paper with Eric Pianka comparing lizard and fish assemblages. Was such a comparison a broader goal right from the start, given the lab you worked in?
Kirk Winemiller: The paper was a part of my dissertation research. As a graduate student I was interested in fish community ecology, but also ecological theory. I became very interesting in the emerging field of food web ecology, and most of the research at that time was motivated by theories about abstract relationship such as complexity and stability. Theories were far outpacing empirical evidence to test them, and most of the empirical datasets were very crude — just ball and stick diagrams involving a handful of species and predator-prey interactions. I wanted to collect data from real communities and produce detailed descriptions of food webs to compare with the theoretical models and resulting “food web laws”. It turned out that my food web research revealed the many methodological and scaling issues that complicate comparisons of food webs. One can even question whether it makes sense to identify an individual food web that can be compared with other such entities. I found that community composition and predator-prey interactions shift in time and space, and it is difficult to bound a system in space and time in a manner that is objective.
HS: Stepping back a bit, could you tell us how you got interested in fishes? I notice that you worked on them earlier, for your Master’s project, as well.
KW: For some reason, I’ve always been fascinated by fish. I can recall from a very young age that I was mesmerized by fish in a fish bowl or small stream. When I was 5 years old, my family moved from the town to the countryside, and I spent much of my youth catching fish, frogs and other creatures from a stream near our house. I also raised tropical fish in aquaria.
HS: If you don’t mind my asking, could you tell us why your PhD supervisor was not an author on this paper?
KW: I designed my own research project and obtained my own funding to do the research. I actually had two major advisors for my PhD studies, and both were incredibly helpful and great scientists. However, they were not actually involved in my food web study.
HS: How did you choose to do fieldwork in the Venezuelan Llanos and the Atlantic lowlands of Costa Rica?
KW: I wanted to work in the tropics where fish diversity is very high. I was lucky to find opportunities to conduct research in both of those countries. At a conference, I met a professor from a Venezuelan university, Donald Taphorn, and he invited me to help me do research there. He was enormously supportive of my efforts. I was introduced to Costa Rica during a graduate field course, and it seemed a good place for a foreigner to do field research.
HS: Have you been back to these sites since the time when you worked there for this study? When as the last time? In what ways have they changed since then? For example, if you went back to the locations in Figure 1 and took photographs today, how would they look? Does ‘Quebrada’ have another name now?
KW: I continued to work in Venezuela for many years. My students and other collaborators have researched many different questions involving fish and rivers throughout the country. As the socioeconomic and political situation deteriorated in the late 1990s, we were forced to discontinue our work in Venezuela. Sadly, most of my professional colleagues who are Venezuelan have left the country, but a few remain, and they face a difficult situation today. I returned to Costa Rica several times over the years, usually accompanied by students conducting research projects.
HS: From the description of your methods, it seems to have been a lot of work! When you think back to those field days, what are your most striking memories? Any particular incidents that you remember vividly? Did your PhD supervisor visit you when you were doing fieldwork?
KW: My most vivid memories of the research for the food web project are sitting for hour after hour and day after day at a microscope with preserved fish specimens while doing stomach contents analysis. I dissected several tens of thousands of fish specimens to determine what they ate, and to estimate the volumes of diet items. At the same time, I recorded data on gonads and reproductive status, which ultimately was used for an analysis of life history strategies. No, my supervisors did not visit me in Venezuela or Costa Rica, although I did invite Dr. Pianka to accompany me to the Venezuelan Llanos region a couple of years after I graduated. We had a memorable field trip.
HS: You deposited your specimens in museums in Venezuela, Costa Rica and Texas. What is the status of your collections today? Have you had the chance to visit these museums and see them after your study?
KW: I still examine the specimens that were deposited in the Texas Natural History Collection in Austin. One of my current students has been borrowing many specimens in order to take measurements for his research project. One of my former students did research in Costa Rica, and she examined some of my specimens in the ichthyology collection in San José. The collection of the Museum of Natural History in Guanare, Venezuela, is one of the largest and best in all of Latin America. Donald Taphorn was the founder and curator of that collection, but he left Venezuela around 2000 and has not returned. The collection is being maintained by colleagues at the university there, but without resources and without visits from scientists who need to use the material, its future is uncertain.
HS: You use the formula of Adams et al. 1983 to calculate trophic levels for fish species. Today, do you still use this formula or some variant of it in your work? Similarly, do you continue to use a version of the computer program you used for building the food webs in this study?
KW: The Adams et al. formula works perfectly fine with dietary data. Yes, we have used that formula in several studies. The programs used to calculate food web statistics was created to run on Apple computers that are obsolete today, and the code was never revised for more modern machines. So it is not used anymore. Another reason it is not used is that comparisons of food web statistics has lost its appeal in more recent years, and that is for the reasons I mentioned in answering your first question.
HS: You acknowledge a long list of people at the end of your paper. Could you tell us a little more about who these people were, how you knew them and how they helped you?
a. G.H. Orians — gave me advice when I was exploring research ideas
b. D. Haydon — helped write the food web computer program
c. D.L. DeAngelis — gave me advice
d. S.L. Pimm — gave me advice
e. D.C. Taphorn — supported my efforts in Venezuela
f. L.G. Nico — assisted me with fieldwork in Venezuela
g. A. Barbarino — assisted me with fieldwork in Venezuela
h. E. Urbina — assisted me with fieldwork in Costa Rica
i. C. Martinez — assisted me with fieldwork in Costa Rica
j. L.K. Winemiller — assisted me with fieldwork
k. P. Rodriguez — assisted me with fieldwork in Venezuela
l. N. Greig — assisted with fieldwork in Venezuela and Costa Rica
m. K. Sherwood — wrote the code for the first version of the food web computer program
n. J. Martinez — assisted with logistics in Costa Rica
o. E. Chamorro — assisted with logistics in Costa Rica\
p. H. Haug — supported my efforts in Costa Rica
q. F. Mago-Leccia — supported my efforts in Venezuela
r. C. Hubbs — gave me advice
s. P. Urriola — supported my efforts in Venezuela (landowner of a study site)
t. R. Schargel – supported my efforts in Venezuela
u. F. Cortez — supported my efforts in Costa Rica
HS: How long did the writing of this paper take? When and where did you do most of the writing?
KW: I spent about 6 months preparing the tables, figures and text for the manuscript. Most of this was written during my last year of the PhD program. Several months later I revised the dissertation chapter for submission to a journal.
HS: Did this paper have a relatively smooth ride through peer-review? Was Ecological Monographs the first place this was submitted to?
KW: Ecological Monographs was the only place this was submitted. Amazingly, this paper received very little resistance from reviewers and editors. I recall that they liked it very much. I think the time was just right for ecologists to receive this evidence and lesson about comparative studies of “real” food webs. My conclusion was a cautionary — theory was outpacing empirical evidence.
HS: Would you remember what kind of attention this paper received when it was published?
KW: I received messages from a few ecologists. I recall very well that Gary Polis was one who contacted me to congratulate and learn more.
HS: What kind of impact did this paper have on your career and the future course of your research?
KW: It had a very great impact. It remains one of my most cited papers. In 1993 I won the Mercer Award from the Ecological Society of America for that paper.
HS: Today, 27 years after it was published, would you say that the main conclusions of this study still hold true, more-or-less?
KW: I believe that the conclusions definitely hold true, and the lessons remain relevant as ecologists continue to seek better ways to study “real food webs”.
HS: If you were to redo this study today, would you do anything differently? Would you use different methods to sample fish?
KW: I would not change any aspect of the field or lab work related to fishes, however, I would have like to have acquired dietary data for invertebrates, birds and other components of the system. However, it was a daunting task to work with so many fishes as things stood. More recently, my lab employs stable isotope methods to study food web ecology — which is much faster and easier than dissecting thousands of fish specimens and examining fragments of food items under a microscope.
HS: In your paper you highlight the incompleteness of the food webs you built primarily due to the difficulty of sampling diets of many taxa and omission of rare species. Subsequent to this study, were you able to build more complete food webs for these areas? In general, could you comment on the improvement in our abilities to build accurate food webs in the last 27 years?
KW: One of my former students studied an estuarine food web, and he examined gut contents of both fishes and macro invertebrates. It was very time consuming and laborious, but he did it (I tried to dissuade him at the beginning). As I mentioned, now we can use stable isotope analysis to discover certain things about food web ecology, but even that method has its limitations.
HS: In the paper you say that it is too early to make generalizations about the scale-invariance and “C as a function of n” because of the quality of the data. Today, do you think we can have such generalizations been attempted?
KW: I now feel that it is a fairly useless endeavour to attempt to quantify the density of trophic links in a food web. There are too many sources of bias in such data. How does one bound a food web? When do we count a link? When do we count a species as present in the local food web? What is local? I could go on and on. There are more interesting an approachable questions in food web ecology.
HS: Towards the end of the paper you reflect on the future of food-web research and suggest many improvements to further the field. Today, if you look back to the 27 years since this paper, how satisfied are you with the way the field has evolved?
KW: I am a bit dismayed that some ecologist have carried on to this day with attempts to compare food web features based on studies conducted using different criteria, methodologies, spatial scales, temporal scales, and scales of resolution for consumers and resources. In many cases, these critical influences are not even mentioned. However, food web ecology remains a vibrant field of study, and there are new approaches to address new questions. I mentioned stable isotope analysis, but experimental approaches, and new kinds of ecological models also are breaking new ground.
HS: Have you ever read this paper after it was published? If yes, in what context?
KW: On occasion I have looked for bits of information in the paper to use for things I’m working on. Sometimes I’m a little impressed that I wrote some of the passages — I think the statements were clearly expressed and some points remain valid and relevant.
HS: Would you count this paper as a favourite, among all the papers you have written?
KW: I’m certainly very proud of that particular paper, and mostly because of the hard work and time that went into it. The best accomplishments in life are from the things that are most difficult! I also think that I was a bit lucky with the timing of that study. Food web ecology badly needed more robust empirical evidence.
HS: What would you say to a student who is about to read this paper today? What should he or she take away from this paper written 27 years ago? Would you add any caveats?
KW: I would say that the questions asked in that paper remain relevant, but the approaches needed to answer them will need to be more multifaceted compared to what I did. We need descriptive work, experimental work, and modelling in order to understand the structure and functioning of trophic networks. Also, a good question and a good study system for which one has passion make hard work seem not so hard, and long tedious hours seem shorter and even exciting.