Note from Jeremy: This is a guest post from Mark Vellend.
I wrote a book on community ecology while on sabbatical last year. In a paper published a few years ago I communicated the core theme: the huge number of models, ideas, and theories in community ecology can mostly* be boiled down to different combinations of just four “high-level” processes – selection, drift, dispersal and speciation. This core idea leads to what I think is a different and more conceptually coherent view of theoretical community ecology, and the book was my attempt (an experiment of sorts) to see if it “works”. Of course I think it does, but you all can be the judge eventually.
While writing the book, I read hundreds of papers and book chapters and books**, spent countless hours pondering what they all collectively have to say, and so generated far more in the way of thoughts and ideas than could reasonably fit into a shortish book. Chatting about these with Jeremy last year prompted the idea of some guest posts on DE, which I decided was a good idea, both for the normal public-benefit reasons of provoking thought and discussion in the scientific community, and also for the selfish reason of perhaps piquing enough interest among DE readers to increase book sales (available in late summer 2016 from Princeton University Press!). (I can assure you there’s no financial motivation here: I will make no more than a few dollars off of each book sold, which I promise to pay you back with a beer at a conference if you bring the book to use as a coaster.)
So, here’s one line of questioning I find quite interesting. Why do some ecologists (such as myself) envy the theoretical state of evolutionary biology? Is this affliction justified?
First off, why evolution envy? On Team Evolution we have Darwin (natural selection) and Mendel (heredity), and then the Modern Synthesis that ties everything together into a lovely coherent whole in which the models all boil down to different combinations and manifestations of four main processes: selection, drift, gene flow, and mutation (sound familiar?). Who wouldn’t want to be on that team? Notwithstanding modern developments that have led some to question the adequacy of the Modern Synthesis, it’s a beautiful thing and a huge attraction of the field of evolutionary biology. As a result, evolutionary biologists all speak the same theoretical language, so there’s a feeling of oneness in the discipline that must make them all feel warm and fuzzy all the time (and perhaps a smidgen smug)***.
Ecology, in contrast, has splintered into innumerable sub-disciplines (e.g., population vs. ecosystem ecology) and sub-sub-disciplines (e.g., food-webs and coexistence of competitors within community ecology), each of which has its own distinct dialect, such that practitioners can hardly communicate with one another, and everyone spends excessive amounts of time arguing why their sub-sub-discipline is more important than the next. Who would want to be on that team? In community ecology (the focus of my book), one consequence of this is that students have great difficulty figuring out the connections between island biogeography, resource-competition theory, the intermediate-disturbance hypothesis, and multivariate ordination (just to name a few topics one might cover under this umbrella). The number of models and hypotheses keeps growing every larger, with reductions (i.e., global rejection and discarding of hypotheses) exceedingly rare. So, it’s a conceptual basket case.
Focusing on the “micro” portion of evolution and noting that population genetics theory is the conceptual core, then a great quote from Van Valen and Pitelka sums it up nicely: “Unlike population genetics, ecology has no known underlying regularities in its basic processes”.
Next question: Is evolution envy justified? Another way to approach this question is to ask: is evolutionary biology actually “better” at anything than ecology (as opposed to just being more aesthetically pleasing)? If so, then surely we are justified in having evolution envy. This question potentially opens the huge can of worms regarding what constitutes success in a given branch of science (no doubt Jeremy will point to old posts about this here, here, here, and here), but for now let’s just think about the ability to make predictions. I’m thinking specifically about predicting the future state of some biological system based on knowledge of its current state and the processes that cause it to change.
Despite its lovely theoretical apparatus, I’m not sure evolutionary biology is any better than ecology at making good predictions. (Actually, I have no idea, which is one reason to write a blog post and hope for illuminating input from you all.) Here’s a hypothetical example: if we know that someone is about to start dumping nutrients into a lake or that fires will become more frequent in some terrestrial ecosystem, how well can we predict the future states of ecological variables (e.g., community composition, total biomass) vs. evolutionary variables (e.g., intraspecific distributions of heritable traits, allele frequencies)? It seems to me that we can actually make half-decent ecological predictions, even if this is sometimes based only on predicting that the same thing will happen as the last time someone dumped nutrients in a lake (does that count?).
However, for any individual species, we might be highly uncertain even about whether it will persist (and therefore have the chance to adapt – although I guess that’s also a failed ecological prediction), and if it does persist, whether the direct selection pressure (nutrients or fire) will be countered or magnified by indirect effects (e.g., changing abundances of other species) and whether the adaptive significance of particular genes or traits is altered in the novel conditions, thus making predictions bunk or at least valid only over exceedingly short time scales. No doubt we could also list predictive successes of evolutionary biology (e.g., HIV treatment; please offer more in the comments), but hopefully I’ve made my point clearly enough: it’s not clear to me that we’re all that good at predicting future evolutionary trajectories of populations.
At the end of the day, does Team Evolution actually come out ahead of Team Ecology? What are the shining examples of success in each discipline? Should evolutionary biologists actually have ecology envy rather than vice versa? I’d love to know what you think.
*the book largely concerns communities of species on the same trophic level or at least those potentially competing for the same things (e.g., space), but this is not the place to get into all that.
** I use the word “read” in its broad sense, including (very light) skimming.
*** If it’s not obvious yet, I’m doing some tongue-in-cheek role-playing here – communicating extreme stances on things just to be provocative. I may or may not believe any of it.