Posted by: Jeremy Fox | January 1, 2012

Why are some ecological ideas controversial?

Why are some ideas in ecology much more controversial than others? You might be tempted to say that “Ideas which apparently conflict with other ideas, or with empirical data, will be controversial.” But I think that’s wrong—in ecology there seems to be very little correlation between the amount of criticism or controversy surrounding an idea, and the theoretical and empirical support for that idea.

Just off the top of my head, here’s a list of some ecological ideas that were, at least for a time (perhaps a long time), very controversial, but for reasons largely or entirely unrelated to the available evidence:

  • Interspecific competition. Debate over the importance of competition, and how to test for it (the “null model wars”), was famously intense in the late ’70s and early ’80s. This despite the fact that there are good theoretical reasons to expect competition (see any introductory ecology textbook), and the fact that, when you do a removal experiment to look for interspecific competition, you usually find it (Schoener 1983, Gurevitch et al. 1992).
  • Density dependence. Intense as it was, the debate in community ecology over interspecific competition was nothing compared to the debate in population ecology over density dependence. But here again, you would have a hard time arguing that the debate was driven primarily by data, or even by conventional theoretical considerations—it was ultimately a reflection of very deep-seated conceptual commitments (Cooper 2007).
  • Trophic cascades. As a grad student in the mid-’90s, I lived through the “top-down vs. bottom-up wars”, as they were sometimes called, although the issues actually went beyond the question of whether communities are “mostly” structured by top-down or bottom-up forces (see the special feature in the June 1992 issue of Ecology). Even just 20 or so years later, it’s hard to understand why there was so much fuss. The most basic question—Are top-down and bottom-up effects common?—has a clear-cut answer. When we look for trophic cascades, in both aquatic and terrestrial systems, we mostly find them: removing predators causes their prey to increase, which causes the prey of those prey to decrease (Shurin et al. 2002). When we look for bottom-up effects, we mostly find them too. As for pretty much every other question, such as those about the determinants of the strength of top-down and bottom-up effects, either all the proposed answers are either unimportant or wrong, or else the available data are totally inadequate to test them (Borer et al. 2005). So rather than having silly arguments about particular cases (see, e.g., the amusingly contrasting views of Pace et al. 1999 and Chase 2000 on the implications of Spiller and Schoener 1994), we ought to be either coming up with better answers, or better data. NutNet is leading the way on the latter.
  • Neutral theory. Evolutionary biologists enjoyed the neutralist-selectionist debate so much that community ecologists decided to refight the debate themselves. And just for fun, they decided to fight it using a particular kind of data (relative abundance distributions) which evolutionary biologists had already found to be inadequate to the task of distinguishing neutrality from non-neutrality.*

Contrast the above—intense controversies that arose and often persisted in the absence of much data, or even despite a pretty clear-cut empirical consensus—with the history of the intermediate disturbance hypothesis, which has never been a very controversial idea despite a horrible empirical track record (much worse than that of trophic cascades, density dependence, interspecific competition, or neutral theory), and being based on outright logical fallacies. Or think of keystone predation, the prevalence of which has been the subject of active research and ordinary scientific discussion, but never vociferous debate, even though the empirical evidence could hardly be considered to be more clear-cut than that for, say, trophic cascades.

The same question about the origin of controversies could be asked in other fields as well.** I’m no expert, but as far as I know sexual selection and sexual conflict was a pretty well-developed body of evolutionary theory, well-integrated with a fair bit of data (Arnqvist and Rowe 2005). Not a topic that would seem ripe for a big controversy about fundamentals—until Joan Roughgarden created one pretty much single-handedly.

And that’s probably part of the answer. If someone really prominent says something controversial, lots of people often pay attention. In ecology, Don Strong had a prominent role in the controversies over both interspecific competition and trophic cascades, and Steve Hubbell pretty much single-handedly kicked off the neutral theory debate. In evolution, Gould and Lewontin single-handedly created controversy over the “adaptationist programme”. But personal fame isn’t sufficient. In evolution, I don’t think many people paid much attention to Lynn Margulis’ stranger claims about “symbiogenesis” as an alternative to natural selection. And in ecology, Hal Caswell proposed a version of neutral theory in 1976 but as far as I know failed to kick off anything like the recent controversy over Hubbell’s neutral theory.

So, when this blog makes me massively famous and influential, what controversy would you like me to create? Because with great power comes great responsibility. 😉

*I actually think it’s very valuable that ecologists now collectively have a much better sense of what sort of dynamics distinguish neutrality from non-neutrality. I just think we learned it the hard way.

**And in fact it has. But I haven’t read the enormous social science literature on this. You get the background research you pay for on this blog.


  1. Happy New Year, Jeremy!

    I can think of plenty of existing ones… but I’ll limit myself to just a couple, which you’re free to develop.

    (1) Empirical vs theoretical ecologists: All your models are wrong vs all your data are belong to us crap. A microcosmologist’s take might also incorporate the “model experimental systems are crap compared to natural systems” vs “the natural world is too bloody messy to study rigourously” that’s been discussed elsewhere already.

    (2) Single vs multi-trophic level community/foodweb models. You’ve touched on this above (interspecific competition), and it’s a personal bugbear of mine, with some reviewers dismissing some of my papers because the models don’t include predation. “But all models are wrong!” I want to shout. “And you forgot to include all the other important interactions in your (stupid) wrong model (mutualisms, parasitism, intra-guild predation, …)”. I think it’s far more important to see what we can learn from the different approaches than simply dismissing those that don’t include our favourite interactions.

    But I suppose these are existing controversies. Why don’t you create a controversy that’s sexy right now. The irrelevance of ecological dynamics for evolution and vice-versa.

  2. Just klicking on some of your links showed me that Joan Roughgarden published her kick-off paper in Science, whereas Hal Caswell published his non-controversy-starter in Ecological Monographs. Maybe a second requirement to start a controversy is to publish in … you know which ones.

    • Nah. Hubbell’s neutral theory was first published in Coral Reefs after Nature rejected it. Only when his book came out did the controversy begin. And IIRC, the battles over intersp. comp. and density dependence did not really involve Nature or Science papers.

      • I think that also speaks to the role of editors in the way that science operates. Joan Roughgarden can easily publish her work whereas Hubbell was rejected. I don’t know if you remember last year’s “Don’t judge species on their origin” debated kicked off by Nature, but the editors were begging for the authors of that paper to be more controversial and they had to pull back! Nonetheless, that still catalyzed a rather ferocious debate that still exists today. It is important to realize that the scientific processes has a strong subjective human component so we can begin to recognize that and fix our flaws rather than just denying them.

  3. There are NO controversial ideas in ecology, and there never have been. You are just creating a controversy by bringing it up. 😉

    Seriously though, I think you pretty much answered your own question, i.e. some combination of a lack of quality data to address the topic at hand, which leads to various forms of complex hand waving, combined with the principal one way that the human ego manifests its need for attention in the academic environment. Pretty straightforward I think.


  4. Jeremy, thanks for another good post.

    I think a common ingredient in ecological controversies is an attempt to make inferences about important processes from easily collected survey data. All of your examples (except maybe trophic cascades) have this in common. It’s hard to resist the temptation: Go out and collect some observational data and then conduct an ingenious analysis to answer a fundamental process question. It fuels controversy because the claims can’t be supported (typically many other processes can produce the same pattern) and, because the data are easy to come by, the debate attracts lots of participants. I think the moral of the story is that if we want to learn about processes, we need to study them directly instead of giving in to the temptation of pattern interpretation.

    • Preach on Peter!

  5. belated comment by an amateur reader — I’d bid for coming up with a highly complicated model of the deep biosphere in which elaborate specialized structures are built in the pores of the rock by bacterial communities, slowly, over vast time, accomplishing great things as cooperators. Take off from straightforward observations like

    and elaborate from there to assert finding evidence by looking at the structures that bacteria are busily trying to form on the inside of oil pipelines after being ripped out of their environment and call those evidence of self-assembling complexity then extrapolate back to what they could have been doing way down where they came from.

    Maybe it’s more of a science fiction novel than an ecological controversy; perhaps both?

    • Hmm…bit outside my field, sorry.

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  7. I fist think that these controversies showcase great strides in our field. A stronger scientific field is one that uses controls, and in complex, adaptive, large experimental settings like those in our field, adequate controls can be difficult or impossible to implement. An adequate supplement is using a modeling approach to act as a null or neutral model greatly enhances our understanding of the biological processes that we wich to understand and predict. So maybe Connor and Simberloff v. Diamond or Hubbell v. deterministic ecologists did not ADD to our understanding of ecological phenomena, I think that they tempered our experimental processes and interpretation of our data.

    P.S. Hubbell told me once that he had no idea why his version of NT was the one that rose to fame, as opposed to Caswell or Bell. I think that he thought is was a random draw.

    P.P.S. Biologists really love to attack Margulis. Remember that she had endosymbiotic theory rejected by over a dozen journals before she was able to publish one of the most important biological discoveries of the past century. Remember that symbiogenesis at the ecological scale, like virtually all evolution, is intangible. But view the origin of new variation, forms (e.g., hybrid speciation), and other punctuated evolutionary events (a.k.a. “major transitions” sensu Maynard Smith) in a symbiogenetic context highlights that symbiogenesis is a concept that must be included in our understanding of large-scale biological diversity and form.

    • That’s a very interesting remark of Hubbell’s. He could well be right.

      Sorry, I have no idea what your point is about Margulis. I don’t know what you mean by “symbiogenesis at the ecological scale”, or what it could possibly mean for it to be “intangible”. Nor do I know what it could possibly mean for “virtually all evolution” to be “intangible”. I don’t know what you mean by “origin of new variation”, but from the context I’m guessing you don’t mean “mutation” or “recombination”. I don’t know what you mean by saying all the various things you list can be “viewed” in a “symbiogenetic context”, or what you think this context highlights. And “major transitions in evolution”, as defined by Maynard Smith, are not synonymous with “punctuated” evolutionary events or the other things you list.

      I’m sorry if this seems too blunt, but I think you’re using vague arm-waving where it would be much more useful to talk in a concrete and detailed way about specific claims of Margulis’ for which we do or do not have evidence. For instance, we have strong evidence of the symbiotic origin of mitochondria and chloroplasts. Yes those claims of Margulis’ were initially rejected–and now they’re in the textbooks. This is the way it generally works with major scientific claims that cut against the conventional wisdom. It is *not* an injustice to Margulis that her claims about mitochondria and chloroplasts were initially rejected, that’s just a reflection of the conservative nature of peer review. We *want* peer review to be conservative, otherwise the literature would be rife with mistakes. Most radical claims that get rejected in peer review (such as many of Margulis’ other claims) are rejected because *they really are wrong*.

      If you sincerely believe that there are other claims of Margulis’ which continue to be rejected despite strong evidence for them, please state those specific claims and the evidence. For instance, we do not, to my knowledge, have any evidence at all for the symbiotic origin of any other organelles, despite Margulis and her students spending many years looking for, e.g., genes in other organelles. We certainly have no evidence for, and massive evidence against, new species emerging from hybrid matings between distantly-related species, a concept Margulis supported by backing a now-retracted PNAS paper.

      • Jeremy, so seem to be very confused by my post, so allow me to clarify several things for you.

        Substantial evolutionary (including symbiogenetic) changes are not measurable or observable on ecological timescales and are therefore not perceivable (hence my use of the work “intangible”).

        The contemporary evolutionary literature uses “variation” to mean much more of the classical “variation” and “recombination.” Variation is a premise for evolution to work, and there need not be reason to narrowly define it as just genetic. There are other genetic means (e.g., genome duplication) and the past couple of decades have shown many other non-genetic means that produce variation for evolution to act. So variation was meant to be read in a context for evolution to work. Is that more clear?

        Also, most of the major transitions DO include symbiogeneitc forms–endosymbiosis, sociality, multicellularity, and sex.

        Your second paragraph you describe the crux of this post–that even with evidence ideas can be controversial and rejected. At heart, this is an un-scientific approach. For Margulis to have ample evidence to describe endosymbiotic theory and to be rejected as controversial speaks to that.

        I disagree that we want peer review to be conservative. I think that we want it to be fair, neutral, and examine ideas and not the people or their beliefs.

        “. . . we do not, to my knowledge, have any evidence at all for the symbiotic origin of any other organelles” Other organelles? So Margulis gets a bunch right and your arguments is that she did not find more?

      • Thank you for clarifying what you mean by “intangible”. But now I’m unclear why “intangibility” in this sense is relevant. Nothing I said has anything to do with what does or does not occur on ecological timescales. I hope you don’t mean to claim that, because putatively “symbiogenic” evolutionary events occur rarely, or occurred in the distant past, that we have no way to study them or test whether they really were symbiogenic or not. For instance, the laughable claim of instantaneous origin of new species via an extremely rare hybridization of distantly-related species in the distant past would leave easily-detectable signatures in the genome of the new hybrid species. Much as mitochondria and chloroplasts arose as symbionts in the distant past–and we know this because of the very-tangible genetic signature those past events left, in the form of mitochondrial and chloroplast genes.

        I am well aware of various mechanisms, established and speculative, by which heritable variation can arise. Much of this literature is these days termed “evolutionary developmental biology.” Some of this literature is controversial, some not. None of it has anything to do with symbiogenesis. You appear to define “symbiogenesis” roughly as “anything that, in your view, wasn’t sufficiently emphasized in the neo-Darwinian synthesis”. I do not think it is useful to lump together all the evolutionary mechanisms that weren’t emphasized in the neo-Darwinian synthesis, and using this definition of “symbiogenesis” makes it very difficult for me to engage constructively with your comments. For instance, the massive body of theoretical and empirical work on the evolution of eusociality has nothing to do with symbionts. And please don’t respond to this point by arguing that Lynn Margulis defined “symbiogenesis” this way, because if she did then that would simply mean that her definition was equally overbroad. I could well have used this definition of “symbiogenesis” in my old post on overly-general concepts in ecology and evolution.

        Yes, of course we want peer review to be fair. Peer review can be both conservative and fair. Peer review mistakes happen sometimes–this is not unfair, but merely inevitable. You have provided no evidence that peer review was unfair to Lynn Margulis. It seems to me that, in the end, peer review did a very good job of sorting Lynn Margulis’ true, well-supported claims from her untrue, unsupported claims. This is surely perfectly fair. Just as it would be unfair to someone for their true claims to be rejected for no good reason, it would be equally unfair (favoratism) to someone for their false claims to be accepted for no good reason. I’m sure you’ll deny it, but frankly you seem to me to be arguing that reviewers should’ve shown favoritism toward Lynn Margulis, based on her work on mitochondria and chloroplasts.

        You seem to be having difficulty understanding what I’m claiming about Lynn Margulis. As should have been obvious from my comments, I am NOT criticizing her for failing to get even more things right than she actually did get right. (That would be an extremely bizarre criticism) Here is a short, hopefully-clear list of the claims I would make about Lynn Margulis:

        1. Lynn Margulis was right about the symbiotic origin of mitochondria and chloroplasts. The scientific community eventually accepted these claims.

        2. That the scientific community initially rejected Lynn Margulis’ claims about mitochondria and chloroplasts before accepting them was not unfair to Lynn Margulis. It merely shows that peer review is conservative, and occasionally makes mistakes.

        3. The scientific community continues to reject many of Lynn Margulis’ other claims, which are contradicted by large bodies of evidence. This is not unfair to Lynn Margulis.

        4. Lynn Margulis deserves, and received, great credit for her remarkable and hugely important discovery of the symbiotic origin of mitochondria and chloroplasts

        5. Lynn Margulis deserves, and has received, criticism for overgeneralizing from her success with mitochondria and chloroplasts, making or backing many claims which are contradicted by large bodies of evidence.

        6. Far from being ignored or unfairly treated, if anything many of Lynn Margulis’ incorrect claims were more widely-discussed than they deserved to be based on the evidence for them, especially late in her career. This was thanks to Lynn Margulis’ fame as the discoverer of the symbiotic origin of mitochondria and chloroplasts.

        I believe my comments have been very clear. If I do not respond to any further comments you provide on this issue, it means I have decided that further exchanges between us would not be productive.

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