As part of my #ESA100 reflections, I commented that variance partitioning was dead as a way to infer the drivers of metacommunity structure. Mathew Leibold didn’t get what I was on about at all. Understandably–my remarks were brief and in retrospect not as clear as they should’ve been.* He was kind enough to take the time to comment at length on what he sees as the main problems with variance partitioning and how it’s currently applied, which gave me the chance to clarify my own views. I agree with Mathew on many points.
Wanted to highlight this exchange because I think it addresses an important issue in ecology. Understanding metacommunities is a really important job for community ecology, and right now variance partitioning is probably the single most popular tool for the job. It’s vitally important that we use that tool in effective ways, improve it if we can, and have a good understanding of what it can’t and can’t do. Mathew and I agree that:
- There’s been excessive enthusiasm for using variance partitioning as a diagnostic test for metacommunity theories. There are too many possible “kinds” of metacommunities–far more than the small number of “paradigm” special cases on which existing theory focuses–for variance partitioning to be used as a diagnostic tool.
- Insufficient attention has been given to how to interpret variance partitioning even if various statistical issues with it are addressed. (I’d add–don’t know if Mathew would agree–that this is a common problem in ecology. When a new statistical tool is developed, subsequent work tends to focus on identifying and resolving technical statistical issues with that tool. Which is fine, but tends to have the unfortunate side effect that equally or even more important non-statistical issues of how to interpret the tool tend to get neglected. Or worse, get mistaken for technical statistical issues.)
- Variance partitioning remains a potentially useful statistical tool, and future work needs to focus on how to interpret and use that tool most effectively. (Not as a standalone diagnostic tool, but as one line of evidence among others, I’d say.)
I also think this exchange of comments was a nice example of how blogging can contribute to scientific discussion. So I wanted to highlight it for that reason as well.
*Mathew’s a friend and knows how my brain works. So if he can’t tell what the hell I’m on about, probably lots of other people couldn’t tell either. Which is my bad.