Data from: Habitat filtering determines the functional niche occupancy of plant communities worldwide

How the patterns of niche occupancy vary from species-poor to species-rich
communities is a fundamental question in ecology that has a central
bearing on the processes that drive patterns of biodiversity. As species
richness increases, habitat filtering should constrain the expansion of
total niche volume, while limiting similarity should restrict the degree
of niche overlap between species. Here, by explicitly incorporating
intraspecific trait variability, we investigate the relationship between
functional niche occupancy and species richness at the global scale. We
assembled 21 datasets worldwide, spanning tropical to temperate biomes and
consisting of 313 plant communities representing different growth forms.
We quantified three key niche occupancy components (the total functional
volume, the functional overlap between species and the average functional
volume per species) for each community, related each component to species
richness, and compared each component to the null expectations. As species
richness increased, communities were more functionally diverse (an
increase in total functional volume), and species overlapped more within
the community (an increase in functional overlap) but did not more finely
divide the functional space (no decline in average functional volume).
Null model analyses provided evidence for habitat filtering (smaller total
functional volume than expectation), but not for limiting similarity
(larger functional overlap and larger average functional volume than
expectation) as a process driving the pattern of functional niche
occupancy. Synthesis. Habitat filtering is a widespread process driving
the pattern of functional niche occupancy across plant communities and
coexisting species tend to be more functionally similar rather than more
functionally specialized. Our results indicate that including
intraspecific trait variability will contribute to a better understanding
of the processes driving patterns of functional niche occupancy.