Ecologists, especially community ecologists, are always looking for shortcuts. By which I mean, they’re always looking for ways to make strong inferences about mechanisms and processes, just based on clever analysis of easily-collected or already-existing observational data. In the past, I’ve criticized various such shortcuts: randomization of species x site matrices to infer interspecific competition, plotting coexisting species onto a phylogeny to infer contemporary coexistence mechanisms, plotting local vs. regional species richness to infer whether local communities are closed to invasion, and using the shape of the species-abundance distribution to infer whether the world is neutral. And there are many others I’ve never mentioned, some of which have been refuted by others, such as the use of ordination methods to infer the process dominating metacommunity dynamics (refuted by Gilbert et al. 2010), the use of power law distributions of movement lengths to infer whether foraging animals follow Levy walks (e.g., Augur-Methe et al. 2011) and using body size ratios of co-occurring species to test for stable coexistence via resource partitioning (the latter is an old, “classic” example of a shortcut).
It’s a pain to shoot down dead-end “shortcuts” one at a time. So in the interests of efficiency, I’m going to pose a question: has any shortcut in ecology ever worked as advertised? Can anyone name one?
I emphasize that I’m not talking about methods that are merely suggestive, or one potentially-useful tool among many, or that are useful in conjunction with other lines of evidence, or that are powerful but mostly impractical (e.g., attractor reconstruction, which if memory serves requires time series thousands of points long), or that don’t comprise a relatively simple “recipe” that pretty much anyone can apply in any system (e.g., there’s no set recipe for how to “develop and parameterize a dynamical model of your study system”). I’m talking about methods that, caveats aside, were originally sold and used something like how phylogenetic community ecology was originally sold and used: as a simple, broadly-applicable, straightforward and yet powerful way to infer process from pattern. Methods that were sold and used as a way to cut through the complexity of community ecology and provide a clear, short path to major insights. That’s more or less how every one of the shortcuts listed above was sold and used originally, and none of them panned out. Hence my question: has any shortcut in ecology ever panned out?
Another way to pose the question is to ask: what would have to be the case for a method based solely on observational data to allow more-or-less reliable inferences about underlying causal processes? Is it likely that any such method exists in ecology? If it did, is it possible that it would be simple, broadly-applicable, straightforward, and yet powerful?
Based on the example of successful observation-based sciences like astronomy, which I’ve discussed previously, I’ll tentatively suggest that no such methods exist in ecology. If you don’t have a quantitative, well-validated theory that incorporates all the processes affecting the observations of interest, then you basically have no hope of solving the “inverse problem” of inferring the underlying processes from the observations.
Note that I do think there are cases outside the physical sciences where valid shortcuts exist. I’m thinking of methods like the HKA test and its derivatives, used to test for selection in population and evolutionary genetics just based on gene sequence data (here is a brief reivew). Notably, much as with the case of astronomy, this is a case where we can write down a more or less complete list of the underlying processes that affect the observational data of interest, where we have a rigorous, quantitative theory of how those processes will affect the observed data, and (crucially) where different processes (here, selection vs. drift) are predicted to affect the data in quite different ways, leaving quite different “signatures”. In contrast, a common failing of putative shortcuts in ecology is that the process for which the shortcut purports to test often is only one of many that could give rise to data that look a certain way.
Can anyone name any shortcuts in ecology that actually turned out to be shortcuts, in the sense defined above?