Estimation of inter- intraspecific variation across scales
We used variance partitioning among two factors (Ribas et al. 2006) to
estimate the relative contribution of inter- vs. intraspecific trait
variation at the continental scale by comparing each model (phylogenetic
and environmental) to the combined model following Munoz & Real (2006).
The idea of using variance partitioning to understand intra- vs
inter-specific trait variation was originally developed by de Bello et
al. (2011; see also Leps et al. 2006), but this work focused on
estimating variance from field data in the absence of a model. We use
the traditional approach from statistics by quantifying the proportion
of variance attributable to purely phylogenetic drivers
(σ2Phylo =
R2comined –
R2Env), purely environmental drivers
(σ2Env =
R2comined –
R2Phylo), and the proportion that is
jointly shared between them (σ2joint =
R2comined –
σ2Phylo –
σ2Env).
To quantify the relative effects of environment, species and phylogeny
on inter- and intraspecific trait variation at the regional scale
(eastern US), we used the combined model to estimate the leaf traits for
all individual trees in the FIA data.