A little while back, commenter Holly K shared an interesting view on theory papers in evolution vs. ecology journals:
I am someone very interested in ecological theory in the pure data-free sense. But I think often strategic (general) theory is in the realm of evolutionary ecology, or even just evolution (behavior or speciation theory, for example). Truthfully, I read Am Nat, Evolution, JEB and Proc B much more faithfully than Ecology because I have noticed they tend to publish more insightful theory (including my own, admittedly I am biased!).
Which led to a little discussion in which a couple of people suggested that there’s greater appreciation for theory in evolutionary biology than in ecology. I’m mostly a dabbler in evolutionary biology, but I share the impression that theory in evolution isn’t seen as some separate subfield the way it often is in ecology. I share that impression in part because it seems like evolution journals publish a mix of theory papers and data papers, whereas ecology journals publish one or the other.
But rather than rely on possibly-erroneous impressions, I decided to compile a bit of data. I went through the Jan. 2015-May 2015 issues of two top evolution journals (Evolution and J. Evol. Biol.), five top ecology journals (Ecol. Lett., Ecology, JAE, J. Ecol., and Oikos), and a top journal publishing in both fields (Am Nat).* I counted up the number of theory papers. “Theory” was operationally defined as a paper based largely or entirely on one or more mathematical models. I didn’t count statistical models, things like Leslie matrices or or integral projection models, or papers that manipulated empirical data to simulate some hypothetical scenario (e.g., randomly deleting species from an observed food web in order to study extinction cascades). I kept a separate count of papers which developed a theoretical model, but also tried to parameterize or test it with quantitative data from some specific system or other. Fortunately, there were only two or three papers in the whole set for which I was in any doubt about how to classify them.
Here are the results, along with some brief comments. I didn’t bother expressing the results as a proportion of all papers, because the trends are totally obvious and wouldn’t be qualitatively altered by correcting for number of papers published by each journal.
- Evolution: 13 theory papers. Many but not all were population genetics models.
- J. Evol. Biol.: 10 theory papers, including 2 which used data to parameterize or test the model. One of those two was kind of borderline as to whether it was a theory paper.
- Am Nat: 14 theory papers in ecology, 11 in evolution (counting anything with evolution in it as evolution, which didn’t lead to any weird categorizations to my eye). Six of those 25 used data to parameterize or test the model.
- Ecol. Lett.: 5 theory papers, 2 of which involved data. One of those two was actually evolutionary, despite appearing in an ecology journal.
- Ecology: 1 theory paper. It involved data.
- Oikos: 1 theory paper. But note that I didn’t count the Jan. 2015 issue of Oikos, a special issue devoted to a single topic, which included several theory papers.
- JAE: 1 theory paper.
- J. Ecol.: 1 theory paper, and it’s actually an evolution paper.
The conclusions as I see them:
- Evolution journals really do publish a lot more theory than ecology journals. This is striking to me. They’re sister fields with a lot in common–but they differ greatly in this respect.
- The difference is even starker if you restrict attention to theory papers lacking any data. Only 2/21 theory papers in evolution journals involved data; 3/9 theory papers in ecology journals involved data.
- The differences would be starker still if you didn’t count the two theoretical evolution papers published in ecology journals.
- Am Nat is an outlier in terms of its mix of papers. Much more theory than any other journal on this list, but by no means exclusively theory. A mix of ecology and evolution. And an intermediate fraction of theory papers that involved data.
It’s interesting to speculate on the underlying reasons for these differences.** It would also be interesting to go back a decade or two (or more) and do the same exercise.*** But I think it’s most interesting to speculate on the consequences and implications of the differences.
For instance, which do you think is a symptom of a healthier theory-data interface in a scientific field: leading journals in the field publish both data papers and data-free theory, or leading journals in the field publish little theory, but the few theory papers they publish often include data? I’d probably stump for the former. After all, it’s not as if the data papers in Evolution and J. Evol. Biol. omit or ignore theory–many of them test theoretical predictions. As do papers in ecology journals, of course. So ecology journals are publishing a narrower range of stuff than evolution journals. That suggests to me a greater separation between the theoretical and empirical sides of the field.
This little exercise also reminded me what a precious outlier Am Nat is. I know that some empirically-minded folks think of Am Nat as a theory journal, but I don’t think they should. I think Am Nat fulfills a pretty vital role as the one leading ecology journal where theory and data papers both show up on a consistent basis. Because like it or not, publication venues do still matter. They reflect as well as shape our choices of where to publish and (crucially) what to read. As long as Am Nat exists, it means that empirical and theoretical ecologists still have something in common, because they’re still reading and publishing in the same shared space.
*Yes, of course there are lots of other journals I could’ve looked at. You get the background research you pay for on this blog. 🙂 I didn’t consciously choose journals so as to try to skew things one way or the other, I just haphazardly picked the first few journals that occurred to me. But if you think my results are way off because I didn’t look at Functional Ecology or Ecography or whatever, by all means go compile the data and share it in the comments!
**Presumably part of the reason is the perception on the part of many ecologists that ecology journals other than Am Nat only want to publish “realistic” theory.
***But I’m too lazy to bother. 🙂