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  • Post date: 4 months 4 days ago
    Citation for this post: BibTeX | RIS

    Contributed by Sofía Campana, Georgina Conti, Florencia Spirito and Laureano Gherardi

    The was held on  September 18th to 23rd, 2016 in Puerto Iguazú, Argentina. This small town is known for its proximity to the Iguazú Falls, one of the Seven Natural Wonders of the World. It is situated within one of the biggest remnants of Atlantic Forest, which is a biodiversity hotspot in South America. This natural setting provided a perfect atmosphere for our meeting, which theme was “The challenge of integrating society and nature: proposals from ecology". 

    The Binational Meeting of Ecology is organized every two years by the ecological societies of these two neighbouring countries: the Chilean Society of Ecology () and the Argentinian Ecological Association (). This year, more than 600 ecologists attended the meeting, including undergraduate and postgraduate students, researchers and natural reserve managers from Argentina, Chile, Uruguay, Brazil, Paraguay, Ecuador, Mexico, United States and Spain. The meeting consisted of six plenary conferences, 25 symposia, seven courses/workshops, 27 oral sessions (with ca. 200 speakers) and more than 300 poster presentations.

    The challenge of linking nature and society

    This year, the ecological meeting highlighted a main challenge across ecologists: to address the need to make a theoretical and empirical link in continuous feedback between natural ecosystems and human societies. This was reflected across plenary conferences, starting with Ulysses Alburqueque (Federal Rural University of Pernambuco, Brazil) proposing the need to consider humans as ecosystems engineers in ecological approaches. He showed a controversial framework that generated several interesting questions and debate across attendees. This first plenary was followed by several symposia addressing agroecology, etnobiology, etnoecology, etnozoology, ecological restoration, eco-economy concluding the first day with a plenary conference leaded by Irina Izaguirre (University of Buenos Aires, Argentina) showing the effect of anthropogenic changes in aquatic ecosystems embedded across the Argentinian Pampa.

    A very interesting and enjoyable plenary conference was the one proposed by Patrick Lavelle (Pierre and Marie Curie University, France) showing the complexity of underground systems continuously evolving over time. In this context, conventional agriculture acts disrupting and turning back processes and systems, making soils simpler and poorer in terms of biological activity. He proposed a redefinition of agriculture in particular, and managed landscapes in general, calling for special research attention on the restoration of anthropized ecosystems.

    Plenary conferences called for a change in the general paradigm conducting ecological research in southern South America, as was pointed out by Audrey Grez (University of Chile) and repeated across symposium, oral and poster sessions: there is a bias in ecological studies towards the study of natural ecosystems where managed or disturbed ecosystems are underrepresented even though these managed ecosystems support most food provisioning services contributing to human well being.

    INNGE: “Seeds in the South”

    Last year a small group of young ecologists from Argentina started the South American INNGE sub-group, called “INNGE: seeds in the South”. For our inaugural event we organised the symposium entitled “The ecology and the ecologists to come: challenges and opportunities in the next decades”. We were motivated by our joint vision for the future of ecology, and the slogan of the meeting was a perfect framework for our first symposium as INNGE South America. We invited five inspiring speakers who are leaders in ecological science to talk about three key topics: (i) academia and the role of ecologists in society (, ), (ii) cooperative networks in ecology (), and (iii) science communication beyond scientific literature (). The symposium was a great success and very well attended, with high levels of participation from the audience. After the symposium, a lot of people showed interest in being involved and collaborating with other INNGE activities across South America. It was a great first step for us! At present, we are actively participating together with a group of more than 30 researchers, putting together several ideas and discussions of collaboration, evaluation of the actual situation and future goals of early career ecologists.

    If you would like to collaborate or know more about the group “Seeds in the South”, you could write to:

  • Post date: 4 months 1 week ago
    Citation for this post: BibTeX | RIS

    In published in Animal Behaviour in 1991, , and Carolyn Sanders showed, through an observational study, that: 1. mating success of male peacock was related to the number of spots on their tails; 2. the relation between mating success and number of tail spots was a result of female choice, i.e. females preferentially mated with males with a greater number of tail spots. Twenty-five years after the paper was published, I spoke to Marion Petrie about the making of this study and what we have learnt since about the tail of the peacock.

     Questions sent via email on 1st July 2016; responses received on 21st September 2016

     Petrie, M., Tim, H., & Carolyn, S. (1991). Peahens prefer peacocks with elaborate trains. Animal Behaviour, 41: 323-331.


    Hari Sridhar:  In the Introduction of your paper you cite only three references. One is Darwin. The other two are studies that manipulated a male character and measured mating success. What role did these studies play in motivating your work?

    Marion Petrie: Although Darwin first suggested that the peacock’s train had evolved as a result of female choice, no one had tested this idea. I was working at Whipsnade Park on a study of Chinese Water Deer, and, whilst staying overnight in the park, noticed the free-ranging peacocks displaying in groups (lekking).  I thought that it would be feasible to study the peacocks at Whipsnade (that it would be relatively easy to catch and mark them) and test Darwin’s hypothesis.  The beauty of a lek mating system is that the process of active female choice is directly observable.


    HS: This paper has three authors. How did this group come together and what was the contribution of each author? Who did most of the writing?

    MP: Tim Halliday held a lectureship at the Open University, which was the closest University to Whipsnade Park, and had an interest in mate choice.  I met Tim at a conference and talked about studying the peacocks at Whipsnade.  We wrote a grant application to the to start the study together. This grant included provision to appoint field assistants for the breeding season and Carolyn Sanders acted as my most excellent assistant on the project. The paper was written after the field season and Carolyn was not involved with writing.  It is hard to recall exactly who wrote what, but looking through my files it looks like I produced a first draft which Tim then improved and added to. Tim is also a talented artist and drew all the lovely figures.


    HS: What is the history of the "free-ranging, feral population of blue peafowl at Whipsnade Park"? When were peafowl brought there and what for?

    MP: Whipsnade Park belongs to the Zoological Society of London, and I am afraid that I know very little about the history of the population of the peafowl, although it had been in existence for at least 40 years when I started working there. I know that peafowl born in captivity at London Zoo were brought to Whipsnade, and that Whipsnade provided a home for other peafowl from other sources. The keepers at Whipsnade sometimes caught and sold peacocks.  So my impression was that there were movements in and out of the population, and that this had been going on for some time.


    HS: Have you ever had the opportunity to observe peafowl in their natural range?

    MP: I have been to India twice for short filming trips during the peafowl mating season, and had the opportunity to watch peafowl there, although they were not ringed.  It was possible to observe a “lek” and courtship, and, although I didn’t see an actual mating, it was fairly easy to observe peacocks displaying close together in Sariska National Park. One of the aims of the filming trips was to film tigers and peafowl, so I also went to Ranthambore National Park. I can remember seeing peacocks in flight there…a fabulous sight!  Although I didn’t note any obvious differences in behaviour between Indian and UK birds, there was an obvious phenotypic difference: the peacocks in India tended to have longer legs, and, as a result, held their trains further up from the ground.


    HS: What was a typical day like when you were doing this work? Did you do the trapping and banding and lek observations yourself? Who was Nigella Hillgarth, who you acknowledge "for help in marking and measuring the birds"?

    MP: I don’t think I can describe one typical day because they would vary so much over the year. But some tasks would predominate at particular times of the year. I was heavily involved in catching birds in the months prior to the breeding season, and took all the measurements myself, whilst Nigella held the birds (to make sure the same person took all the measurements).  My memories of this was that it was very cold as we had a small unheated shed to work in, and under these adverse conditions, Nigella and I became great friends.  Sometimes we had large numbers of birds to process all at once, so we would work very long hours. At the time, Nigella was a PhD student working on pheasants in the Zoology Department in Oxford, and was her supervisor.  Nigella was interested in the ecto-parasites of peafowl, and as part of her work, we recorded the number of feather mites drinking at the eyes of the peafowl in a time period. Nigella and I are still in touch, and she is now the president and CEO of the .

    During the mating season, I was heavily involved in watching the birds. The lek watching started in mid-April and continued until the end of May; Tim and Carolyn also covered some of the watches.  The aim was to arrive at the lek early in the morning, before peacocks left their roost sites, and continue until the males stopped displaying, around the middle of the day. This could mean very early starts for me, as I was living in Norfolk at the time, and it was a 100 mile drive to the Park. We would watch from a small canvas hide, sitting on a small canvas chair, but sometimes we had to kneel to move round the hide, in order to follow females moving between males situated around the hide.  Watching the birds was extremely interesting and stimulating.  There was always something new to see, and many observations would make you ask ‘why are they doing that’? Some observations would provoke analyses that contributed to a paper.  An example of this was the observation that certain females would sit by particular males and engage them in courtship at times when another female tried to approach them.

    After the mating season I was involved in data analysis and writing up, preparing to give talks at summer conferences, applying for grants and jobs!  This went on until Christmas and then the cycle would begin again.


    HS: The observations ended in May 1988 and the paper was submitted on 8 July 1989. Can you give us a sense of what happened in the intervening one year?

    MP: Whilst the observational work ended in May 1988 for this paper, we were still working at Whipsnade. In April and May 1989, I had four field assistants and we watched at four leks within the park.  After the end of the observation season in 1988 there was a period of analysis and writing the paper first for Nature and then for Animal Behaviour.  The referees requested changes so the paper needed to be revised before it was eventually published in Animal Behaviour On a more personal note my second child was born on 1st August 1989.


    HS:  Was the term "hoot-dash" used for the first time in this paper? Is it still used when describing peafowl mating?

    MP: No, hoot-dash was in the literature and is still used as far as I know.


    HS: Was the photo in Fig. 2 of the "hoot-dash" taken in Whipsnade park? Was Chris Pierpoint a professional photographer?

    MP: Yes it was, and Chris was one of the four excellent field assistants working in 1989 and was a very good photographer.


    HS:  Did this paper have a smooth ride through the publication process? Was Animal Behaviour the first place you submitted it to?

    MP: We first submitted the paper to Nature but it was rejected, so we rewrote the paper for Animal BehaviourNature has a very strict word limit, so the first draft of the paper for Nature was a lot less expansive than the Animal Behaviour version. 


    HS: You acknowledge Morris Gosling and Robert Gibson for "comments on an earlier draft". Could you tell us who these people were and how you knew them?

    MP: and I worked together on Chinese Water Deer at Whipsnade and on lekking in Topi in Kenya.  He is also my long-suffering husband.  is a colleague who has done some outstanding work on mate choice and lekking in sage grouse.


    HS:  How did the collaboration with , for the female choice null model, come about?

    MP: I gave a talk at the Zoology department in Oxford and presented the data on the sequence of males and females visited.  Alan attended the talk, came up to me afterwards and kindly offered to analyse the data as it is now presented in the paper.


    HS: You say "a large part of the variance in mating success can be attributed to train morphology and that females choose to mate with those males that have the most elaborate trains of those sampled". You also say "Our data do not suggest that competition between males is an important determinant of mating success". Today, 25 years after the paper was published, do these statements still hold true for peacock mating behaviour?

     MP: I do think that there is good evidence for these statements from the data that we collected at that time.  Whether it is ‘true’ for all peafowl everywhere is a different question, and whilst some studies have found the same positive relationship between train morphology and mating success, at least claims that no such relationship exists (although, they did find a non-significant positive correlation).  Of course, if females do not prefer peacocks with elaborate trains it does raise the question of why the peacock’s train has evolved, and I haven’t seen any good data that support any alternative hypothesis.


    HS:  In the Discussion, you highlight many questions for future research - how females assess males, why do females choose males with more elaborate trains, what determines whether males obtain a display site, how do males choose leks - have these questions been addressed since? 

    MP: I do think we are further ahead with these questions:

    Why females choose males with more elaborate trains formed the basis of much of my future peacock work, after the publication of this paper.  I removed peacocks from Whipsnade and bred from them in captivity.  This was a controlled breeding experiment, where each Whipsnade cock was mated with 4 females, and the subsequent eggs removed from pens and artificially incubated and hatched in separate compartments, so we knew the sire for all the offspring produced.  The young were reared in large groups and monitored regularly to record growth.  When the offspring were old enough, they were released into Whipsnade Park and we observed their subsequent survival and future behavior. 

    We also followed the male offspring of the release experiment through to sexual maturity and looked at where males started to display.


    HS:  Your study was entirely observational and with a small sample size (N = 10 males). Since this study, have you had the opportunity to repeat these tests with larger sample sizes and in an experimental way?

    MP: Yes, I looked at the relationship between train elaboration and mating success in a much bigger sample from four lek sites.  I have also removed eye spots of peacocks and shown a change (reduction) in subsequent mating success.  but this has not been cited nearly as widely as the Animal Behaviour paper. 


    HS:  Did this paper create a buzz - within academia and outside - when it was published?

    MP: My memory is that there wasn’t a huge amount of buzz around this paper, although it did get some attention. Other papers that I have published created a bigger response in the media, such as showing evidence for improved growth and survival of the offspring of males with more elaborate trains.


    HS: How important has this paper been in your career? Has it had a major influence on the course of your future research?

    MP: I think that the peacock work has had a huge impact on my career and it was certainly critical in my obtaining a NERC advanced research fellowship which I held in Zoology at Oxford and which provided the wherewithal to do a further 5 years of pure research.


    HS: Have you ever gone back and read this paper after it was published? When you read this paper now, what are the aspects about it that strike you first?

    MP: I did have a look at the paper again recently, in response to your questions, and it does seem like something from a different era, where natural history and simple field observations were considered to be important.  Times have changed enormously in academia, and it is now extremely difficult to obtain money to do this sort of work.  This is a shame, to say the least, as there is so much that we don’t know about the natural world.


    HS:  If you compare this paper to papers you write today, are there any differences, e.g. in writing style?

    MP: I am not sure how my writing style has changed, if it has at all, but how you produce papers has changed.

    As you become more senior in academia your job changes from being one where you do everything yourself (from collecting data to analyzing and writing papers) to one where you spend a lot of time applying for grants for other people to work as part of a team.  Your job becomes contributing ideas, reading other people’s work and contributing to that, rather than writing your own papers from scratch.


    HS: Have you had the opportunity to go back to your study site after the paper was published? Are any of the birds you banded still around?

     MP: I wrote a number of papers on peacocks after this one was published in 1991, and this involved doing several years more field work at Whipsnade. However, in 1996, I moved to a new post at Newcastle University, and once I moved to the North-East, it was logistically difficult to continue working at Whipsnade.  I continued to work on peacocks at a peacock farm in Norfolk.  I have been back to Whipsnade once, a few years ago, and saw very few peafowl.  Apparently, there was a big cull when there was an avian flu scare in the UK, as the keepers were worried that avian flu could be passed from the free-ranging peafowl to other animals in their collection.  I saw one of my marked birds, and it was begging at one of the restaurants in the park.  Flint pit paddock still exists, but it is no longer full of peacocks.


    HS:  This paper has been cited 360 times (Google scholar) as of today. Do you keep track of these citations, and do you know what this paper gets cited for, mostly?

    MP: I do not look at the citations of this paper very closely nowadays, but think it is usually cited as evidence for female choice. Although this is not universal, and in my experience, what people actually cite in a paper sometimes has more to do with what they are trying to say, than what you have actually said!


    HS: What would you tell a student who is about to read this paper today? Any caveats? What should he or she takeaway from it?

    MP: Probably the most important parts of the paper are the data on individual females.  These show two things: one is that females don’t mate with the first male that they approach; they always look at more than one male and this is very good evidence for female choosiness.  The second is that they mate with the male that has the highest eye-spot number of those visited.   This suggests that the male’s train has something to do with their choice, although it is not necessarily eye-spot number that is being assessed, and it may be something that is related to eye-spot number. It may also explain why males with relatively few eye-spots obtain matings (by being the best of those sampled), and that this doesn’t always result in a high correlation between train characteristics and mating success either within a lek or across several leks.


    HS: Among all the papers you have written, is this your favourite?

    MP: I wouldn't say that this paper is my favourite. The first paper I wrote from my PhD work will always have a special place in my heart and that iswhich was published in Science in 1983.






  • Post date: 4 months 2 weeks ago
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    In 1971, published in Ecological Monographs providing experimental evidence for the role of physical and biological disturbances, as well as competition, in influencing an intertidal community off the west coast of USA. Forty-five years after the paper was published, I spoke to Paul Dayton about the making of this paper and the impact it has had on his career and our understanding of intertidal communities.

     (Questions emailed on 3 September 2016; responses received on 25 September 2016)

     Citation: Dayton, P. K. (1971). Competition, disturbance, and community organization: the provision and subsequent utilization of space in a rocky intertidal community. Ecological Monographs, 351-389.


    Hari Sridhar: How did you become interested in marine ecology?

    Paul Dayton: I grew up living a life mostly outdoors, first in Arizona, as my father worked on a ranch and in a deep gold mine, and then moved to Oregon where he worked first in logging camps, eventually trying to make a living selling life insurance after moving back to Arizona.  In the logging camp era we started making Christmas trips to a, then very remote, bay near Guaymas, where I learned to snorkel, in 1952, when I was 11 years old.  At that time marine life was not well known, as scuba gear was still being developed by in Europe. To me it was also scary initially.  I had spent most of my life outdoors and was very familiar with terrestrial systems, but this was utterly new and a huge challenge and I was hooked!


    HS: Through reading the and looking at your website, I came to know that this paper formed part of your PhD at the University of Washington. What was your motivation to work on intertidal communities for your PhD?

    PD: This is independent of the last question. I was already committed to marine ecology and was working with , but my thesis was also much influenced by ’s emphasis on basing ecology on the study of evolutionary processes.  I was also influenced by a paper by about the importance of testing hypotheses, as Paine was doing. But it is hard now for modern ecologists to understand how absolutely dominated ecology was by the dogma that all evolutionary ecology was a result of competition.  It was an over-reaction to a long history of density-independent dogma and an ecological focus on using environmental physiology to explain the distribution and abundance of species. But instead of focusing on processes such as predation, facilitation as well as competition, there was an aggressive focus only on competition.  This was because the first focus on evolutionary processes was led by charismatic physicists and mathematicians who really did not much care for understanding nature as much as having their models used, and their models were bounded in ways that were not very receptive to predation and facilitation, and many of them went to some effort to downplay the importance of these more realistic processes.  I am very dyslexic and was totally unable to understand the beauty of their math, and most models seemed rather irrelevant to the natural world as I perceived it, thinking with pictures as dyslexic people do.

     When I first came to graduate school I was diving around Friday Harbor, but the underwater system that I could relate to was already spectacularly studied by , an excellent student finishing his thesis at the time. So I focused on the intertidal, but focused on some poor questions relating to sea anemones. But in so doing I was also working at sites around Makah Bay where Paine was working.  Along with Platt, all of us were much influenced by ’s intertidal work, which was very influential in supporting the competition paradigm.  But as I crawled around the intertidal habitats of the Washington outer coast and San Juan Islands, I did not see much competition; rather I saw various types of disturbances that ameliorated most potential competition.  The potential for space competition was obvious, but many agents that disrupted the competition also seemed common.

     Ecology has grown into a discipline of very good, but also very specialized, scientists. Fortunately, I was not influenced by these specialties, and was able to crawl around the very different intertidal systems in the region and try to figure out what processes were at work in each place.  And there were all sorts of important factors influencing the patterns.  I was most interested in biological questions such as predation, or disturbance such as limpet bulldozing young barnacles and eating small algal recruits, or the facilitation of specific algae that served as nurseries for mussel spat, or refuges from desiccation such as anemones for snails, creating zones of intense snail predation that differed from areas with no anemones.  Another form of facilitation was algal overstories sheltering a whole community of small algae. But of course there was some competition, especially in the lower algal dominated levels.  But one of the things that is lost by specializing on specific processes, or, importantly, working in a limited number of habitats, is an appreciation of the huge importance of non-biological factors.  Every place I worked was physically different, and the differences included the obvious influence of wave exposure and the many critical oceanographic factors determining the recruitment, growth and survivorship of the plants and animals. There were also differences in the rock substrate running from soft sandstone to hard greywacke sandstones to various igneous rock types, and these differences can structure the settlement patterns with all of the subsequent biological interactions. On top of this, in my own areas, the battering by drifting logs was also an important factor. So really, a dyslexic naturalist crawling over this habitat sees all sorts of processes going on at the same time, and the entire spectrum of processes changes from site to site.  I did my best to test and describe these processes, missing a lot.  The most important lesson for me was that while the habitats are different, the fundamental processes themselves can usually be seen, but they have different ecological strengths from place to place. To really understand the bigger picture, it is good to be able to work in different habitats, to compare the different interactions strengths.  But this personal appreciation for seeing the big picture is why I think that those non-naturalists focusing on their statistical dogmas have done so much damage to a general understanding of natural systems.  I would say the same thing about those working only with models or in the laboratory.   Surly appropriate statistics, models and laboratory research can be extremely valuable, but only when they are tied into real natural history.

    Sorry for the long rant responding to a simple question!


    HS: If you don't mind my asking, how come your PhD supervisor - Robert Paine - wasn't an author on this paper?

    PD: I don’t mind your asking, but really I think you should unask the question and instead ask why is it that most ecologists slap their names on anything they can, including their students research.  In those days none of the good ecologists put their names on their students’ papers.  I don’t think Paine ever put his name on a student’s paper, nor do I remember Joe Connell doing so, nor nor or any good ecologists of the era.  I did not do so either. Joint authorships were done when you genuinely worked together on a project, and I put Paine on as he contributed a lot.  So the real question is why it is so common now, and the obvious answer is that our “fame” seems to depend on number of papers and citations rather than the creative breakthroughs or important advances to a field.  I like to think that the colleagues I care about are able to evaluate my “worth” based on, both, publications and independent students not dragging my name around as a “!”  The problem is that our bureaucrats are too lazy to do their jobs well, and want to be dazzled by metrics such as numbers of papers irrespective of whether the papers say anything worth while or those stupid H values that reflect nothing of much importance that I can see.  And nobody any more keeps track of successful students we mentor, and here is where I want to stake my legacy. 


    HS: Do you continue to visit and work in the sites that you sampled during this study?

    PD: I so wish I had done so.  I always wanted to but only got back a couple times. I offer the normal excuses: I was busy with other time-consuming projects, mentoring wonderful students who really mentored me, and I was totally committed to spending my summers camping with my kids until they got into high school.


    HS: Would you remember how long the writing of this paper took and where you did most of the writing? Apart from your supervisor, Robert Paine, were there other people who you were regularly discussing your work with at the time?

    PD: Good question. I got a tremendous amount of mentoring by Bob Paine, Joe Connell, and Bob Fernald, but most of my real learning came at the hands of graduate students.  Graduate students shared large offices and most of us did our writing at home.  I wrote it all by hand, as I write badly and it needed lots of smoothing.  My cohort of graduate students, especially , , and broke their butts trying to teach me math and theory – that they failed is no fault of their own as I now understand the severity of my dyslexia.  In the end, my good wife did all of the statistics in the paper, and helped with my prose. I finally sat in the kitchen and painfully typed all of the piles of scribbles, and my committee did an excellent job reading it and helping me make it literate!  But it did not really take very long, as I had thought about it a lot and knew pretty much what I wanted to say.  I think I started writing in February and was mostly finished in early summer.


    HS: How were the figures in the paper drawn?

    PD: By hand!  In those days we had sets of frames that we used to draw lines, curves and letters, but they were all carefully traced by hand.


    HS: Could you give us a sense of what your daily routine was during the fieldwork for this study? Did you mostly work alone or did you have people to help you?

    PD: Entirely alone.  I worked in two areas that were several hours from Seattle, where I had to return to teach labs for my salary until the end. It is documented in my thesis, but I think I was in the field over 60% of the 5 years I was in graduate school. The outer coast sites were rainy and difficult to get to, but very rewarding and fascinating for their high diversity and all of the fascinating interactions.  The tides were often in the middle of the night, and I spent the day fishing for Salmon from Bob Paine’s tiny boat.  I slept and ate in my small 4-wheel drive vehicle.  The San Juan Island sites were much dryer and more difficult to work because the rock was so hard. I struggled to maintain the cages.  But there I had the luxury of a house to stay in and I was better able to work up data and get caught up.  I spent my free time solo diving, looking at sea star foraging biology.  At the time, I think I was stressed trying to keep up with all the driving and fieldwork and keeping up with the data, but in hindsight those were absolutely the best times of my life.  and he kept reminding me how lucky I was, and he sure was right.


    HS: Did this paper have a relatively smooth ride through peer-review? Was Ecological Monographs the firs place this was submitted to?

    PD: Yes and Yes!  I marked up the actual thesis very carefully, in the first month of my job, the generous Department secretary retyped it, and I submitted it within a few months of defending the thesis.  The reviewers were and Joe Connell and both were very careful and constructive and helped me in many ways, but it went right through.  I don’t know who reviewed the , and , but they were all very constructive and I did not have the nightmare that many young students experience now.  The people in Paine’s generation were very constructive and helpful, but unfortunately those of my generation seem hyper-critical and often hostile.  I very much regret this situation.


    HS: Could you give us a sense of what kind of impact this paper had on your career and on the future course of your research?

    PD: The Ecological Society of America recognized it with their Mercer Award, which meant a lot to me.  In the beginning, it did not have much effect on my career and I am not sure it influenced my tenure promotion.  By that time, I had published several pretty good papers from the inter-tidal, the Antarctic and the kelp system.  I would expect that the Mercer Award helped with the promotion, but I don’t think many people have actually read the 1971 paper, even though it is heavily cited.


    HS: Today, 45 years after it was published, would you say that the main conclusions of this paper are still true, more-or-less?

    HS: Yes. Even without the reasonable caveat of putting it back to the state of the science then, I immodestly think that the conclusions are pretty much true today.


    HS: If you were to redo this study today would you do anything differently?

    PD: I would write it very differently.  It is heavily cited but not read.  People cite and recycle something apparently without realizing what I had done.  Sometimes this is reader laziness, but in this case there is no doubt that the paper is very hard to read. That is entirely my fault. I still struggle with my prose, but I dearly wish I had struggled a lot harder with that paper, perhaps breaking it into several papers. 

    The other thing I would emphatically do differently is bring in all the different strengths of the processes as one goes across this huge environmental gradient from Tatoosh Island to Colin’s Cove.  I was so entrained into the battle with the competition folks that I focused too narrowly on my message, that in the real world nature is much more influenced by disturbance than resource competition.  I drove thousands of miles working the two areas at the same time and really completely failed to discuss the obvious lessons about the physical effects of the shifting environmental conditions across that gradient.


    HS: You say "The most important physical factors correlated with differences in the relative distributions and abundances of the important sessile species in the intertidal are (1) wave exposure, (2) battering by drift logs, and (3) physiological stresses such as desiccation and heat". Today, do these three factors continue to be the most important?

    PD: If I said that it represents another terrible omission. Most of the focus of the paper and my career is on the various evolutionary roles of biological interactions: competition for potentially limited resources, predation, disturbance, and facilitative interactions.   Certainly those three factors are critically important, but I would also add biological interactions!


    HS: This paper is today a 'citation classic'. At the time when you were doing your work did you anticipate at all that it would have such a big impact on the field? Would you know what the paper mostly gets cited for, i.e. is it cited appropriately most of the time?

    PD: I was young and insecure and I hoped all marine ecologists would read it and agree with the idea that disturbance trumps competition in most systems.  It took awhile, but eventually I think that the message did get across.  I think that most of the citations I have seen are appropriate and I am very grateful that my peers recognize it.  I think my colleagues are very generous with their citations and I am grateful.


    HS: Have you ever read this paper after it was published? When you compare this paper to ones you write today do you see any striking differences?

    PD: Not really: it is hard for me to read also! Once in a while, I go back and dig something out to remind myself what I did. Surely, it would never even be reviewed now because of its length.  This is probably a good thing because it would be more readable, yet I have always enjoyed my “story telling” approach to ecology, that involves an understanding of the big picture in time and space.  Even as a student I realized how important scaling time and space were, and that would be lost if the paper were to be chopped up as demanded by today's standards.


    HS: Would you count this as one of your favorites, among all the papers you have published?

    PD: I am very proud of the paper and grateful for the recognition.  And I am still proud of the total thesis, although I don’t think it was as good as the one Bob Vadas did before me.  Students then were doing interesting projects and I think that there were many good theses.  Frankly, I am more proud of a couple of my kelp papers, and the one I am most proud of was done in the Antarctic at the same time I was doing my thesis.  , and the reason I am proud of it is that it was done in two brief and difficult field seasons, but we had to reject the entire research paradigm that we based the project on to start with.  We had to switch questions in the field and focused on asteroids and sponges, and in the second season none of our experiments had worked because we totally underestimated the slow growth rates. At that point, I had to find a way to estimate the predation rates and consumptions over a year.  This was done using the ecosystem approaches of the era that I did not know and had to learn in the field in Antarctica.  Bob Paine visited us there, and was very helpful as we struggled to estimate the effects of the predators on the sponge populations.  These days, ecosystem and population people rarely interact, and have developed very different specialties, but being able to synthesize both approaches made that paper possible.


    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 45 years ago?

    PD: I would tell her that this paper is very difficult to read, but it has a lot of interesting information that might be useful to her.  I would explain the value of story telling as a means of understanding nature, and that there are several interesting stories in the paper. I would suggest that as she reads it she copies the table of contents and lists the various vignettes or stories in the paper, and at the end see if she can synthesize those that are of interest to her into a big pictures story that makes sense. 


    HS: Thanks so much!

    PD: My pleasure, sincerely.  Thanks for including me in your project.  I just did this at home and realize it is more complete than I would have done in an interview because I had to write it in short bits of times getting the grandkids ready for their sabbatical!  But I kept thinking that if there is anybody interested enough in the paper or in me, that there are a lot of fun stories in the I did with .  The dynamite story comes to mind as something that is simply not conceivable today and people find it amusing.  If it is possible I suggest that you send them to to read it if they are interested.




  • Post date: 4 months 3 weeks ago
    Citation for this post: BibTeX | RIS

    In in Nature, , Heather Bryga and , showed, through an 11-year experiment on a natural population of guppies in Trinidad, that predators can cause significant life-history evolution. Twenty-six years after the paper was published, I spoke to David Reznick about its making, the influence it had on its career and what we have learnt since about life-history evolution in guppies.

    (Interview conducted via Skype on 28th July 2016)

    Citation: Reznick, D. A., Bryga, H., & Endler, J. A. (1990). Experimentally induced life-history evolution in a natural population. Nature 346: 357-359.


    Hari Sridhar: Before this study, you had already done a lot of work on life-history and evolution in this system. What was your motivation to do the work presented in this paper in relation to all that you had done before? At what stage in your career did this come?

    David Reznick: My original motive for going into research was to test some aspect of the theory of evolution in nature. And to do experiments. Evolution had largely been dealt with as a historical discipline, or in work on model systems in the laboratory, like fruit flies. I felt that it should be possible to look at evolution in real time. I was originally inspired by work by on , which was coming out in the 1960s and 70s. Janis was seeing evidence for evolution on timescales of centuries, but I felt that something more might be possible, based upon what I’d learnt in population genetics. My earlier papers that led up to this were really to develop the potential to do this experiment. The first question was to consider the natural history of guppies in Trinidad. I had been to a seminar by John Endler where he had talked about localities where guppies lived either with or without predators, and how the predators had shaped the evolution of male colour patterns. What I took from that talk was that those localities differed in the risk of adults experiencing mortality. When there are predators, adult male guppies showing colour were at risk of being eaten, but when predators were absent, males that were mature and showed colour were at much less risk of being eaten. That’s the only way Endler could have gotten his result. For me that paired well with life history theory. There’s a body of theory developed in the 70s that predicted how life history should evolve in response to a change in the risk of adult mortality. This work on guppies gave me a link to a specific facet of evolutionary theory that made a prediction. It meant that I could make that prediction and test it. The first step was to actually see whether or not there is a pattern in nature that was consistent with the prediction - whether or not guppies that lived with predators were on average younger at maturity and more rapidly developing and devoting more resources to reproduction than ones that lived without predators. That’s what the earlier papers had accomplished.


    HS: You said you were inspired to do this work after hearing a seminar by John Endler. Do you remember when and where this was?

    DR: I do. The talk was given at the in October 1977.


    HS: At this time, had you already finished your PhD?

    DR: I was doing my PhD at the time and I was working on a very similar problem. I was working on mosquito fish from Illinois and North Carolina and New Jersey and looking at life histories and variation among populations in life histories. And it was approaching the point where I might have been able to do something like I did in guppies. I had found farm ponds in Illinois with introduced mosquito fish, of which some had and some did not have sunfish (family Centrarchidae) in them. So the question was whether or not there is evidence of life history evolution there. So when I went to John’s seminar, my mind was primed, and his system was much more attractive for a variety of reasons. I was beginning my fourth year of graduate school, but after I saw his seminar I wrote the sort of proposal that we were encouraged to write for our qualifiers as second year students. And I gave it to my committee in December that year and asked them to consider letting me change my PhD project. They liked the paper. They thought it was very good and worthwhile for me to, not really discontinue the work on mosquito fish, but to put it on a back burner, and switch to guppies. So the guppy work papers published in 1982 and 1983 were from my PhD thesis, which I submitted in 1980.


    HS: And did you continue working on guppies for your postdoc?

    DR: Well no. At the point when I finished my degree I had no papers and got nowhere on the job market. But I had this idea to transplant guppies and predators and study evolution in real time. So I wrote a proposal to the National Science Foundation (NSF), but I wasn’t allowed to be a principal investigator on the proposal. So I found somebody whose name I could put down as Principal Investigator and submitted it before I finished my degree. Then by the time I finished my degree, the proposal was funded and it included my salary. I was then, what I described as, an incipiently unemployed research scientist, meaning that I was paying my own salary with my grants.


    HS: This paper has three authors – you, John Endler and Heather Bryga. How did this group come together?

    DR: The connection with John Endler was his seminar in 1977. I went out to dinner with him that night and said: I have this idea based upon your work. He was very supportive. I first went to Trinidad in 1978 - in March and April of 1978 - and he was there then and guided me. He gave me all the kind of background I needed to be able to work there - he took me out to the field, showed me how to identify the fish, showed me where I could go to collect what I wanted, etc. And I continued to interact with him after that point. In fact, the experiment in the 1990 paper is one that he initiated in 1976, which he talked about in the seminar I saw, and based on which a publication came out in 1980. So there is a natural and continuing connection between us.

    Heather Bryga was my lab technician. She was an undergraduate who started working with me when I began as a faculty member in UC Riverside in 1984, Later I was able to hire her and pay her as a full-time technician with my continuing support from the NSF.  Heather was the one who oversaw the lab work. I was still in the lab a lot those days but not always. She is the one who sort of kept things on track.


    HS: In the paper you say you reared the descendants of these fishes through two generations. Where was this done? Did you bring the fish back to the US?

    DR: Yes. It’s interesting, I was looking at the paper the other day and thinking - Nature papers had, I think, a 1200 word limit, because of which you can’t see what you need to see in that paper. So the key sentence, where it says that, refers you to earlier papers. You would have to go to the earlier papers to read the methods. What I did was I collected wild adult females from the two sites, brought them back to the laboratory at the University of California, where I had a lab in the Biology Department vivarium.  The experimental side of the lab was really like a fish file system since I had hundreds of two-gallon aquaria and reared one or a few fish per aquarium.  I isolated each female in her own aquarium. Guppies store sperm, so each female produces a series of litters of babies, and they became a numbered pedigree. I reared them to maturity and separated males and females before they matured so I had virgin stock. Then I did crosses among the different pedigrees.  The cross design was such that each wild caught female was equally represented, and all crosses were unique. There was no sib-sib mating. So it meant that my first lab generation was mated to produce the second lab generation that evenly represented the genetic diversity of the original sample from the field. The goal in doing that was to separate out environmental effects and maternal effects from what I wanted to evaluate, which was genetic differences among populations. By working on grandchildren, the idea was that the environmental effects and the maternal effects had been separated out. They were no longer confounding feature of the design.


    HS: In your email to me, you mentioned that you are going back to Trinidad soon. I'm assuming that means you are still working there. Do you continue to work in the same sites that you sampled in this study?

    DR: No, our main work now is located in a neighbouring drainage.  We have gone well into the headwaters of what’s called the Guanapo River. We still do, sometimes, work in those old sites. Those sites are a living resource and all the introduced and evolved populations are available for sampling. For example, we have a proposal that will be submitted this week, to study the genetics of adaptation in guppies. Part of that will be to compare guppies within a river that live either with or without predators, but another part will be to take advantage of the experiments, where we know which the ancestral and descendent populations were. So these sites continue to be a valuable resource for looking at the evolution of various traits.  I and other people continue to use them.  But I’m not doing specific work at those sites.  I just occasionally use the fish for studies.


    HS: Have those sites changed a lot since the time you worked there for this study?

    DR: The Aripo tributary is pretty much intact.  It’s in good shape, and the main site downstream where we collected the guppies that lived with predators is okay.  But other parts of know, right now what I’ve heard is that in the last year, a land squatter -  I mean somebody who didn’t own the land but  has cleared a section of forest nearby –might have modified the lower channel of the tributary that was the basis of that 1990 paper. This has happened before; I’ve seen people come and try to garden there. It’s hard because it’s not very good soil and its very steep. In the past they have used it for a year or two and given up and left. Further back in the forest the site is still in very good shape; there is no serious modification there.  But a lot of the sites I used to work on in Trinidad have changed considerably. In the other introduction that I started in 1981 on the El Cedro River, the downstream control - the ancestral site - is very severely modified by human activity.


    HS: Are these sites protected?

    DR: Well [laughs] technically they are National Forest and should be protected, but they are not.


    HS: Could you tell us a little about how the writing of this paper happened. Did the three authors ever get together in one place, or did all the discussion happen over the phone?

    DR: I wrote the first complete draft on my own. At that point, John Endler was in Santa Barbara, which is, about, a 2.5-3 hour drive from here [Riverside]. So I just drove to Santa Barbara and we sat down at John’s computer and reworked the paper together. And then I submitted it.  I can’t remember if Heather Bryga read or commented or participated in the writing at all.


    HS: Do you remember how long it took you to write the first draft?

    DR: That’s interesting. I, actually, got the results in 1988. But the inconvenient event at the time was that I was getting a divorce, so I wasn’t able to work on it as quickly as I would have otherwise. I think, I wrote the first draft fairly quickly. I can write reasonably quickly and I don’t think I spent more than, maybe, four sessions of a couple of hours each to write that paper.  Then, when I met with John, I think we spent 2-3 hours working on it together on his computer.


    HS: That is really quick! At that time, did you have a specific writing routine, i.e. with regard to when and where you wrote?

    DR:  Yes, I write in the morning. I do things like outlining and working on figures and tables and things like that in the night. In terms of writer’s block, I always tell myself that outlining isn’t writing. Outlining is just putting your ideas down and I can do that any time of the day.  So I tend to work on outlines of papers and sketch out the order of ideas in the evenings, and then I get up and do the writing, the actually sentence construction, in the morning.


    HS: Where do you write, usually?

    DR: At that time, I was living in Riverside, in a small town house that I had just gotten, and did all the writing there, at the dining table.


    HS: Did this paper have a relatively-smooth ride through peer-review?

    DR: Yeah, it did.  I got word of it when I was in Trinidad. They just asked for some small changes. It was not controversial, in that regard.


    HS: How did you make the figures for this paper? Did you hand-draw them?

    DR: 1990.. No, I think I just used some kind of computer program we used for drawing figures then. I think Heather Bryga did those figures, or certainly helped with them.


    HS: How was the paper received when it came out? Did it get a lot of attention?

    DR: Oh my, it changed my life. It appeared and the World Herald Tribune and in many other newspapers. I was called to do a TV interview, but I couldn’t make it. They woke me up at 8 am and asked if I can be in downtown LA at 9 am! I, also, got many invitations for seminars. It did a lot to help establish my career.


    HS: Why do you think this study attracted so much attention?

    DR:  Because it showed evolution in real-time. You take it for granted now. It’s like no big deal now to say – ‘Oh, I study contemporary evolution', since so many others have done it. But what people don’t realise is that this change in how people would respond to the study today versus in 1990 is what you could think of as a paradigm shift. When I proposed the experiment in 1980, in the original grant I wrote for the NSF to do this experiment, people used to smile at me and say – "it’s a good idea and we hope you live long enough to see something happen." Even , who is a very prominent evolutionary biologist, saw me present this in a seminar in 1984 and said - "I hope this works.  It’s a good idea.” It seemed like I was expecting a lot, to be able to see any kind of change over such a short time-scale.  The ' work was coming out just then.  Their work was 1980-81 and it was getting a lot of attention. Initially, however, they were looking at selection, not evolution. They didn’t nail it down as evolution until a couple of years later. But it wasn’t experimental work, and it wasn’t linked to a body of theory that made specific predictions.  So I think the thing that was attractive about my work was that I had a prediction based on a body of evolutionary theory and I went and found a plausible situation in nature where we could test it. By the way, this is the second paper. , on the earlier experiments showing the evolution of male life history traits, and it got no attention at all.  This was from the the El Cedro river experiment, but in that we looked for evolution after only four years.  That seems kind of bold now, but I was an assistant professor looking for tenure, so I figured I would take a chance and see if it worked. And it did work, in the sense that the male traits had evolved, but there was no evolution of female traits.  The 1990 paper was based on an eleven year experiment, and there the female traits showed up. But if you look at Table 1 in this paper, you will see the 1987 experiment is also in the left hand column. That’s from the earlier paper.


    HS: What kind of impact did this paper have on your career?

    DR: I think it made me known in my university. And it got me a lot of seminar invitations. I had linked it to my earlier papers, so it attracted more attention to the whole sequence of the work. But I will tell you what the biggest impact was, which I find hard to talk about. My choosing to become a scientist didn’t go over well in my family.  For them, it was okay if that’s what I wanted to do, but my father wanted me to go into the family business or to veterinary school, which I had gotten admission into. Becoming a scientist seemed like an eccentric and not so meaningful thing to do. But you know, even though they didn’t understand my work, seeing me in the newspapers gave it legitimacy in their eyes. You don’t usually hear about this, but that really was, more than anything, the most important consequence of that paper.


    HS: How did this paper influence the future course of your research?

    DR: The other thing I was trying to work on at the time, which I was having some success with, but which I didn’t publish till much later, was the demography of natural populations through mark-recapture.  Up until this point in time, the assumption was that if you live with a predator your probability of dying is higher. That seemed reasonable,   but I wanted to actually prove it.  So between 1986 and 1990 I got NSF money for detailed mark-recapture work.  I was marking guppies using acrylic latex paint that I made less viscous by diluting it with . I found that, in a lot of these streams, the probability of catching a fish if it was alive was exceedingly high. Said differently, the odds of not catching the fish were so low that I could interpret the number re-caught as being very close to the number still alive. So it became a way of estimating mortality rate and I could show that, in fact, mortality rates were higher in streams with predators.

    There was a major revolution in how people perform and analyse mark-recapture data that came between when | began and finished the work. The new statistics let you discriminate between causes for not seeing an individual in a given census. It may be because it died, emigrated or was present but not caught.  If you sample properly you can get independent estimates of all of these things.  I had collected data in a way that would allow me to know if emigration or escaping capture were important issues because they could bias the data, but I had not collected data in a form amenable to the new sorts of statistics. This means there was a special burden to address these potential sources of bias.  I delayed publishing so I could add some extra experiments to convince people the data were okay.

    One inspiration for the delay and extra work is that I presented my results at a conference in France with one of the founders of the new theory in the audience (J.D. Lebreton).  He raised his hand and announced that he did not believe I could catch all of the fish.  The extra work I did showed that I can, indeed, come so close to catching them all, and that the data were okay.

    The weird thing though was - and didn’t come out until 1996 - that the shape of the mortality curves for the high- and low-predation guppies was not what it needed to be, to be consistent with the original theory that predicted how life history should evolve. The original theory was based upon differences among age-classes in risk of mortality. And what I found was that in high-predation localities, all the age-classes had a higher risk of mortality to an approximately equal degree. And the theory I was using said they shouldn’t evolve, and that you couldn’t get evolution unless there was heterogeneity among age-classes in risk. At first, the result was upsetting, but then I realised – ‘Well no, I had seen them evolve!’ I had already done it. And so it wasn’t a question of whether or not they evolve, or whether or not predation had anything to do with it, but it still said that there is something more going on. And that has led directly, in two ways, to the kind of work that I’m doing now. First, the reason the low-predation life history evolves is not because of the lower risk of mortality, but because of the indirect effect of population densities being much higher and depleting the environment of resources. It’s a version of what people now call eco-evo. interactions. In 2006, I got the biggest grant I’ve ever got - a multi-investigator grant - to use guppies to evaluate the importance of eco-evo. interactions in a natural ecosystem. That was a partnership that included theoreticians, geneticists and ecosystem ecologists.  That work still goes on. The second thing was that, once we perfected the mark-recapture, it became possible to repeat the kind of introduction experiment we had done earlier, but to begin with marked individuals. We could then census them monthly, mark all new recruits, save scales from each of them, and get DNA from the scales. Using the DNA, we can construct pedigrees, quantify individual reproductive success and look at evolution in a very different way, i.e. as variation in individual reproductive success. Then we could associate this variation in reproduction with individual-based traits we had measured. One of the nice things about this system is that, at each stage, as I learnt more, I was able to use the learning to answer a greater diversity of questions. I continue to work on guppies in Trinidad till today and am, in fact, just finishing a manuscript on them.


    HS: It is now 26 years since this paper was published. Would you say that the main conclusions still hold true, more-or-less?

    DR: Yes, and the result has proved repeatable.  In the new experiments we have four replicates, and we show that it’s happening, but we also have a much better idea about why it’s happening, than we did then.  The aspect of that paper that didn’t hold up was that it was written around the idea that it was differences in age-specific mortality that caused the life-history patterns that we saw.  As I said earlier, we now know that that’s not the explanation. Indirect effects of predators and density regulation are playing a very important role.


    HS: If you were to redo these experiments today, would you change anything, given the advances in technology, theory, statistical techniques etc.?

    DR: Well yes. In the new wave of experiments we did, we did change things. In the earlier experiment, I just collected a bunch of fish and introduced them. Actually John Endler set that experiment up, the one in 1990. I had done the one in 1987. But in both we just collected a mixture of fish and put them in.  What that meant was that we didn’t have complete knowledge of who went in or what their genetic makeups were.  In the new experiments, what I did was to collect juveniles from the source site, rear them to maturity in single-sex groups, mark them, mate them, collect scales from all of them, photograph them and then introduce them. Then we continued with the same mark-recapture for every new recruit. Through this we know we know about individual movements and the community in which they are growing.   And we have their DNA, using which we can work out their pedigree. So the recent experiments are yielding a much richer body of information.  None of this was conceivable when this work was done in the late 70s or early 80s.


    HS: Do you continue to collaborate with John Endler on this work?

    DR: Yeah, actually we do. For a long time we didn’t, but he was the co-Principal Investigator on the grant I got from 2012 through 2016. He is looking at the evolution of colour patterns again, but using all of his new methods that weren’t available in 1980. I could tell you a little bit about that if you want to know.


    HS: Sure.

    DR: So after that work in the 80s-early 90s, John almost became like a neurophysiologist.  He was interested in, sort of, the neurobiology of how organisms perceive colour, and in the innate structure of colour in the environment and how light changes through the course of the day. He developed these predictive models that integrated the perceptual sensitivity of females with the colour spectra of reflectance of the males, to ask whether or not the pattern of evolution would affect the way females perceived males, or how predators saw males.  He was able to show that, in some circumstances, you could become more brightly coloured and attractive to a female but yet not more conspicuous to the predator, because of differences in their visual sensitivities.  In the current experiments, we have two localities where we have thinned the canopy to increase primary productivity which also changes light falling on the stream. The question is whether or not the change in light would affect the colour patterns of males and how they were perceived by females.  John used that as an experimental treatment to look at male colour pattern evolution, and we are now at the point where we can write the papers.  We know that the canopy has a significant influence on the evolution of structural components of male colour, the structural green and blue.  Part of the guppy coloration is structural and part of it is pigments, and we now have clear evidence for the evolution of the structural colouration. John will now be plugging in his models to see whether or not this is predictable based upon the nature of the light and nature of the visual sensitivity of the females.  Darrell Kemp is also playing a big role in this work.


    HS: In one place in the paper you compare the results of the four- year study and this 11-year study, based on which you argue for the need for long-term field experiments. In the years since this paper was published, to what extent do you think that has happened?

    DR: There’s been some. I'm actually giving a Skype talk in October to Florida International University where they have a (LTREB) grant.  That’s an NSF programme that I think came into existence in the 70s.  There is a lot of talk about the importance of long-term work.  Experiments like we are doing, there are some out there, but there aren’t many. The thing that has happened instead is long-term mark recapture on model systems. That’s mostly a British type thing - Soay sheep, red deer of Rhum, the meerkats in Africa, and various great tit populations. Long-term mark recapture on individual populations of birds has really blossomed. There’s a lot of that kind of work.


    HS: Towards the end of the paper you say your results demonstrate "the importance of predation in moulding life history evolution in guppies, though of course other factors may be important." Subsequent to this paper, were other such factors discovered?

    DR: Yeah, the indirect effects that I told you about is one factor. Another is resource availability. When you talk about density dependence what it means is that guppies are adapting to themselves. People don’t usually think about density-dependence that way. The eco-evo. interaction idea was alive dating to about 1961 but it wasn’t mainstream at all.  It was silent in the background, but now this idea is very much in the fore front. That’s the other main factor that emerged with guppies.   I wasn’t thinking of that precisely then but I was wondering about the importance of resource availability, because it seemed to be a feature of the head-water streams versus the downstream localities. The head-water streams are much darker because they have completely closed canopies, which affects light and productivity.


    HS: In the final sentence of your paper you say "The widespread evidence for size-specific predation in other species suggests that this could be a common factor in life-history evolution". Has work after this paper found support for this suggestion?

    DR: That’s a good question. I’m trying to think. In the bird literature, that wasn’t a new idea, conflict between predation and the ability of parents to provision their young. Certainly within the field of bird life history evolution, which is the biggest area where that kind of work is being done, predation emerged as a big deal. was reading the guppy papers at the same time as . It wasn’t original to him but he did more than anyone to develop the idea and show that it was important in bird evolution. I’m trying to think of other organisms. I know that it has turned up. Now, life history evolution has kind of faded in to the background. It’s not a premier topic as it was then, but I think it is fair to say that predation already was and it’s grown since, as an important factor in shaping how life histories evolved.


    HS: This paper has been cited over 800 times. Do you have a sense of what it mostly gets cited for?

    DR: I think for the idea of contemporary evolution and experimental studies of evolution in nature. Like I said you may have always grown up with the idea that evolution is contemporary and you can see it happening in real time. But that was a new idea then, and I think this paper has maintained some interest for helping pioneer that.


    HS: In the 26 years since it was published have you ever read the paper again?

    DR: I actually read it again yesterday because I was meeting with my undergraduates. I don’t always assign my own papers, but I figured it was a reasonable one to introduce them to the system.  Maybe it was because you had made me think of it with your email. But at other times too, I remember looking back at it, every once in a while. I'm always impressed with how brief and simple it was. I don't know if you noticed, but it doesn’t report any sample sizes, which is very embarrassing.


    HS: What strikes you most about it when you read it now?

    DR: The thing that strikes me was that it was simple. I guess I try to write papers like that today as well, you know, have a short simple sentence structure and not clutter it with extraneous ideas. I guess I didn’t realise I had figured that out at a pretty early stage in my career.  I remember, one of the books I read about writing was .  I had read it in 1988-89, sitting at my dining table.  So that was fresh in my mind at the time I wrote this paper. So when I read it now, I’m glad to see did an okay job with it, in terms of simple sentences and being clear.


    HS: Would you consider this one of your favourites, among all the papers you have published?

    DR: Oh yes, it still is. It still serves as a standard I try to live up to, with the work that I do now.


    HS: What would you say to a student who is about to read this paper today? What should he or she take away from it?

    DR: They should take away the idea that evolution is a contemporary process happening in real time, and it’s one that can be studied empirically with experiments in nature. It’s a question of finding the appropriate setting to do it. So the contemporary nature of evolution is probably the most important message. Also, that it’s possible to extract, from evolutionary theory, specific predictions that can be tested in a natural setting. Finally, in terms of how the system has developed over time, it’s also a statement for why it’s good to do things in nature and not just do them in the lab. The lab version of reality is highly abstracted and it cannot capture the range of interacting factors that you see in nature. People will say you do it in the lab because you can control it and be clear about what’s going on.  That’s true, but if you want to know why animals or plants are the way they are in the real world, then you need to work  in the real world, because  the full scope of factors that interact in  shaping evolution can’t be anticipated or replicated in the lab. I made a similar argument one time, way back when people asked me why I wasn’t doing these experiments in the lab. I said it’s because I want to know why things are the way they are in the real world, and I don’t have faith in the lab being able to reproduce that.  The way this project has developed has shown that there’s no way that any lab work could have led me to an understanding of ongoing interactions between ecology and evolution.  You just can’t capture that in the lab. I couldn’t have anticipated that when designing the lab study. Therefore, I think it’s important to work in nature whenever you can.







  • Post date: 5 months 16 hours ago
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    In in The Annual Review of Ecology, Evolution and Systematics in 2000, attempted to “tame” the wide array of models and ideas about species diversity maintenance, especially in the context of species coexistence in local communities. Chesson’s paper went on to become a cornerstone of modern coexistence theory. Sixteen years after the paper was published, I spoke to Peter Chesson about his motivation to write this paper, and how research on species coexistence has progressed since then.

     (Questions emailed on 3rd September 2016; responses received on 18th September 2016)

     Citation: Chesson, P. (2000). Mechanisms of maintenance of species diversity. Annual review of Ecology and Systematics: 343-366.


    Hari Sridhar: Could you share with us your motivation for writing this paper? Was it written following an invitation from the journal?

    Peter Chesson: I wanted to write this paper for several reasons.  The first was that there was a general lack of appreciation of several important ideas in competition theory with regard to what it means for species to have similar niches.  There seemed to be little appreciation that average adaptedness to the environment, what I called in this paper "average fitness," needed to be considered very differently from the details of how a species uses the environment.  It always seemed obvious to me, but it took me years to realize that it was not obvious to everyone.  In addition, I felt there was not enough general appreciation of the theoretical advances that had been made to incorporate the role of environmental fluctuations in coexistence theory. Finally, I felt that although there are lots of common themes in coexistence theory, many people seemed to think of each hypothesis rather differently, when many of them could be united.  These were my motivations.  I was not invited by the journal to write the paper.  I submitted a proposal three times in successive years before it was accepted.


    HS: Stepping back a little, could you tell us how you got interested in the topic of species coexistence? Which came first: an interest in ecology or an interest in mathematical modelling?

    PC: I have been fascinated by ecology since I was a small child.  I developed an interest in mathematics as a teenager, and ultimately decided to do a mathematics degree with the idea of applying it in ecology.  I got interested in species coexistence after seeing 's treatment of it in his book, "". My imagination was captured by 's , but also, I thought there could be a better development of the role of environmental fluctuations than appears in May's book.


    HS: How long did the writing of this paper take? When and where did you do most of the writing?

    PC: It took me about two weeks of concentrated effort to write the paper as I rushed to meet the deadline for submission. Naturally, I had been thinking about the issues for a long time.  Most of the writing was done in my office at UC Davis between teaching terms when I could focus on it.


    HS: You acknowledge for his help on this paper. Can you tell us a little more about how he helped?

    PC: After the paper was submitted, I sent it out to more than a dozen colleagues.  The majority of people who responded were enthusiastic, but had no concrete suggestions.  Peter Abrams gave a series of critical comments that helped me bring out more clearly some of the points that I was making.  I was glad to get these comments from him because of his often critical appraisals of the field as a whole.


    HS: At the time when you were writing this paper, did you anticipate at all that it would have such a big impact on the field?

    PC: I certainly hoped it would have an impact, but I did not expect that the stabilizing-equalizing dichotomy that is highlighted in the abstract would have such a life of its own.


    HS: Would you know what this paper mostly gets cited for? Would you say that most of the citations are appropriate, i.e. that people understand the theory correctly?

    PC: The paper gets cited in two ways.  Most commonly it is "coexistence theory" as a general reference or for a specific hypothesis that authors presume I have discussed in the paper, regardless of whether I actually have.  Naturally, that leads to a large number of mis-citations.  Some citations are for the exact opposite of what it does say.  These are primarily for cases where it takes on the conventional wisdom with the regard to environmental fluctuations or natural enemies, and the citing authors have either not understood what I have said or have not bothered to read the paper.  Other citations are for the stabilizing-equalizing dichotomy, which by the way does not refer to strict alternatives.  A coexistence mechanism can be both stabilizing and equalizing, and this fact is clearly demonstrated with examples in the paper, but this subtlety is often lost.  I think many people get the basic ideas in the paper, but we have a serious problem in ecology that education about theory and the use of models is not widespread or in depth.  Thus, for most people, a deep understanding of the ideas in the paper is not possible. However, the paper itself seems to have inspired some labs and some intrepid graduate students to dig more deeply into theory, and has led to many applications of at least some of the ideas.


    HS: Did this paper have any kind of a direct impact on your career? How did it influence the future course of your research?

    PC: It has not changed any major plans in my research, but it does seem to have drawn more attention to my work.


    HS: Could you reflect on the kind of impact this paper has had on empirical research?

    PC: The most obvious impact I can see is various efforts to investigate the stabilizing-equalizing distinction.  There have also been numerous effects to apply that idea in related areas of ecology and evolutionary biology.  The major impacts may be more subtle in providing the understanding required for better interpretation of empirical studies.


    HS:  If you were to rewrite this paper today, would you update the theory in anyway?

    PC: There is much to update really.  The most obvious update would be the much more comprehensive understanding that we have today on the role of predation in species coexistence.  The paper had just a small section on this.  In effect, it has been updated though in in . Another big update would be more on the effects of spatial and temporal scale, especially spatial scale.  Early in the paper, I make the statement, "Many models of species coexistence are thought of as models of coexistence in some defined local area. However, to make any sense, the area addressed must be large enough that population dynamics within the area are not too greatly affected by migration across its boundary (103). At some spatial scale, this condition will be achieved, but it may be much larger than is considered in most models and field studies."  This is actually a warning against the focus on the "local community" in empirical studies.  At the time, I did not have much to say about how to get around that problem.  But that has changed with the further development of , which provides an adequate framework now for how to deal with multiple spatial and temporal scales including non-stationarity of the environment in space and time, which we need for addressing long-term climate change.  Finally, an update would provide a better guide on how to use the various concepts empirically.


    HS:  In the last sentence of your paper you say "Allee effects in sparse (low density) populations and stochastic extinction in small populations both potentially limit how similar the niches of coexisting species can be when similar niches mean sparser or smaller populations. These possibilities deserve further study as they have the unique property that they would still work when species are equal in average fitness". Subsequent to this paper, have these aspects been researched further?

    PC: In fact, I am not aware of serious research by theoretical ecologists following up the point on Allee effects.  However, the mathematical literature on dynamical systems in ecology has been investigating Allee effects mostly for the interesting nonlinear outcomes in dynamical systems that include them.  None of this, however, is motivated by, or seriously addresses, niche relationships between coexisting species.  The effects of stochastic local extinction on niche similarity of coexisting species have in effect been investigated by and , but I do not think they were influenced by the last sentence of my paper.


    HS: Have you ever read this paper after it was published? If yes, in what context?

    PC: I am constantly going back to it see if I actually spat out clearly some point that I know I had in mind at the time, so I can refer to it.  I sometimes consult the paper when I see a strange citation of it, to see how the citing author could possibly have got that idea.  I do not recall having read the whole thing through though, after I returned the proofs.


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

    PC: Yes, I would count it as a favorite.  I like it because it "says it like it is" without worrying about what reviewers might think.  It seems to have communicated effectively, and I am proud of it.


    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 16 years ago? Would you add any caveats?

    PC: The main thing I would say to a student today is, don't just read it, make sure you understand why it comes to those conclusions.  I would then refer them to updates.  But really, the paper is aging well.



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