Data from: When does intraspecific trait variation contribute to functional beta-diversity?

1. Intraspecific trait variation (ITV) is hypothesized to play an
important role in community assembly and the maintenance of biodiversity.
However, fundamental gaps remain in our understanding of how ITV
contributes to mechanisms that create spatial variation in the
functional-trait composition of communities (functional β-diversity).
Importantly, ITV may influence the perceived importance of environmental
filtering across spatial scales. 2. We examined how ITV contributes to
functional β-diversity and environmental filtering in woody plant
communities in a temperate forest in the Ozark ecoregion, Missouri, USA.
To test the hypothesis that ITV contributes to changes in the perceived
importance of environmental filtering across scales, we compared patterns
of functional β-diversity across soil-resource and topographic gradients
at three spatial grains and three spatial extents. To quantify the
contribution of ITV to functional β-diversity, we compared patterns that
included ITV in five traits (leaf area, specific leaf area, leaf water
content, leaf toughness, and chlorophyll content) to patterns based on
species-mean trait values. 3. Functional β-diversity that included ITV
increased with spatial extent and decreased with spatial grain, suggesting
stronger environmental filtering within spatially extensive landscapes
that contain populations locally adapted to different habitats. In
contrast, functional β-diversity based on species-mean trait values
increased with spatial extent but did not change with spatial grain,
suggesting weaker environmental filtering among larger communities which
each contain a variety of habitats and locally adapted populations. 4.
Synthesis. Although studies typically infer community assembly mechanisms
from species-mean trait values, our study suggests that mean trait values
may mask the strength of assembly mechanisms such as environmental
filtering, especially in landscape-scale studies that encompass strong
environmental gradients and locally adapted populations. Our study
highlights the utility of integrating ITV into studies of functional
β-diversity to better understand the ecological conditions under which
trait variation within and among species contributes most strongly to
patterns of biodiversity across spatial scales.