|Just one example of how genes of large effect explain less than half the variance in traits. This figure is from Hendry (2013) based on data from Rogers et al. (2012).|
|Studies of parallel evolution in fishes ranges from near-perfect parallelism (near 1) to near perfect non-parallelism (near 2). These data are from an early version of the analysis conducted by Oke, Leblond, and Hendry. For details, contact A Hendry.|
|Any value less than 0.7 means that less than half of the variance in the behavior at one time can be explained by variance in behavior at another time. From Hendry (2015) based on data from Bell et al. (2009).|
|Some typically messy biodiversity-ecosystem function relationships (from Loreau et al. 2001).|
In general, it seems that the variance explained by a given factor in ecology is often quite small – about 2.5-5.4% - as revealed by Moller and Jennion’s (2002) meta-analysis of meta-analyses. Peck et al. (2003) later argued that the more important question was “How much variation is NOT explained” and came up with an answer of “roughly half.” Together, these two analyses suggest that ecological and evolutionary variation is multifactorial and that, if we are to explain much of the variation, we need to look beyond single causation. Stated another way, we shouldn’t focus so much effort on single explanatory factors that explain relatively little of the total variance but we should instead embrace multi-factorial causality that can explain much more.
|From Moller and Jennions (2002).|
Reflecting on the above four research areas for which proponents show high enthusiasm but the data indicates low explanatory power, I am reminded of David Queller’s (1995) response to Gould and Lewontin’s anti-adaptationist rhetoric: “That’s well said, but let’s get back to our field work.”