Data from: Elevational range sizes of woody plants increase with climate variability in the Tropical Andes

Aim: The climate variability hypothesis proposes that species subjected to
wide variation in climatic conditions will evolve wider niches, resulting
in larger distributions. We test this hypothesis in tropical plants across
a broad elevational gradient; specifically, we use a species-level
approach to evaluate whether elevational range sizes are explained by the
levels of thermal variability experienced by species. Location: Central
Andes Time period: Present day Taxon: Woody plants Methods: Combining data
from 479 forest plots, we determined the elevational distributions of
nearly 2300 species along an elevational gradient (~209 – 3800 m). For
each species, we calculated the maximum annual variation in temperature
experienced across its elevational distribution. We used phylogenetic
generalized least square models to evaluate the effect of thermal
variability on range size. Our models included additional covariates that
might affect range size: body size, local abundance, mean temperature and
total precipitation. We also considered interactions between thermal
variability and mean temperature or precipitation. To account for
geometric constraints, we repeated our analyses with a standardized
measure of range size, calculated by comparing observed range sizes with
values obtained from a null model.  Results: Our results
supported the main prediction of the climate variability hypothesis.
Thermal variability had a strong positive effect on the range size, with
species exposed to higher thermal variability having broader elevational
distributions. Body size and local abundance also had positive, yet weak
effects, on elevational range size. Furthermore, there was a strong
positive interaction between thermal variability and mean annual
temperature. Main conclusions: Thermal variability had an overriding
importance in driving elevational range sizes of woody plants in the
Central Andes. Moreover, the relationship between thermal variability and
range size might be even stronger in warmer regions, underlining the
potential vulnerability of tropical montane floras to the effects of
global warming.