1.Spatial variation in filters imposed by the abiotic environment causes variation in functional traits within and among plant species. This is abundantly clear for plant species along elevational gradients, where parallel abiotic selection pressures give rise to predictable variation in leaf phenotypes among ecosystems. Understanding the factors responsible for such patterns may provide insight into the current and future drivers of biodiversity, local community structure, and ecosystem function. 2.In order to explore patterns in trait variation along elevational gradients, we conducted a meta-analysis of published observational studies that measured three key leaf functional traits that are associated with axes of variation in both resource competition and stress tolerance: leaf mass:area ratio (LMA), leaf nitrogen content per unit mass (Nmass), and N content per unit area (Narea). To examine whether there may be evidence for a genetic basis underlying the trait variation, we conducted a review of published results from common garden experiments that measured the same leaf traits. 3.Within studies, LMA and Narea tended to decrease with mean annual temperature (MAT) along elevational gradients, while Nmass did not vary systematically with MAT. Correlations among pairs of traits varied significantly with MAT: LMA was most strongly correlated with Nmass and Narea at high-elevation sites with relatively lower MAT. The strengths of the relationships were equal or greater within species relative to the relationships among species, suggesting parallel evolutionary dynamics along elevational gradients among disparate biomes. Evidence from common garden studies further suggests that there is an underlying genetic basis to the functional trait variation that we documented along elevational gradients. 4.Taken together, these results indicate that environmental filtering both selects locally adapted genotypes within plant species and constrains species to elevational ranges based on their ranges of potential leaf trait values. If individual phenotypes are filtered from populations in the same way that species are filtered from regional species pools, changing climate may affect both the species and functional trait composition of plant communities.
Summary data for leaf N studies in meta-analysis
This file contains summary information and calculated effect sizes extracted from studies that measured leaf Nmass and/or Narea along an elevational gradient. Column titles: study, author and year published, see online appendix S1; r, untransformed correlation coefficient (effect size); n. sites, number of sites sampled; indiv.per.site, number of plants sampled per site; n. indiv., total number of plants sampled; n. reg., n used for the regression where r was estimated; by.mass.or.area, which of Nmass or Narea was measured; within.or.among, whether interspecific or intraspecific variation was sampled; pft, plant functional type; biome, which of temperate/tropical/boreal; grad.min, minimum elevation; grad.max, maximum elevation; lat.mean, mean latitude; species, 1 or more species measured; details, notes if necessary.
leafn3.csv
Summary data for LMA studies in meta-analysis
This file contains summary information and calculated effect sizes extracted from studies that measured SLA or LMA along an elevational gradient. Column titles: study, author and year published, see online appendix S1; r, untransformed correlation coefficient (effect size); n. sites, number of sites sampled; indiv.per.site, number of plants sampled per site; n. indiv., total number of plants sampled; n. reg., n used for the regression where r was estimated; sla.or.lma; which of SLA or LMA was given in paper (SLA = 1/LMA); within.or.among, whether interspecific or intraspecific variation was sampled; pft, plant functional type; biome, which of temperate/tropical/boreal; grad.min, minimum elevation; grad.max, maximum elevation; lat.mean, mean latitude; species, 1 or more species measured; details, notes if necessary.
lma3.csv
Raw LMA data
This file contains all the raw elevation-LMA data extracted from each study in the meta-analysis. Column titles: elevation, the elevation in m above sea level at the data point; lma, the LMA value in g m^-2 at the data point; study, a numeric identifier for the study that the data point came from; latitude; the mean latitude for the study; name, a unique identifier (author's name) for the study; lat.lapse, the latitude to the nearest degree of the data point; long.lapse, the longitude to the nearest degree of the data point.
lmaraws.csv
Raw Narea data
This file contains all the raw elevation-Narea data extracted from each study in the meta-analysis. Column titles: elevation, the elevation in m above sea level at the data point; narea, the Narea value in g m^-2 at the data point; study, a numeric identifier for the study that the data point came from; latitude; the mean latitude for the study; name, a unique identifier (author's name) for the study; lat.lapse, the latitude to the nearest degree of the data point; long.lapse, the longitude to the nearest degree of the data point.
naraws.csv
Raw Nmass data
This file contains all the raw elevation-Nmass data extracted from each study in the meta-analysis. Column titles: elevation, the elevation in m above sea level at the data point; nmass, the Nmass value (percentage N by mass) at the data point; study, a numeric identifier for the study that the data point came from; latitude; the mean latitude for the study; name, a unique identifier (author's name) for the study; lat.lapse, the latitude to the nearest degree of the data point; long.lapse, the longitude to the nearest degree of the data point.
nmraws.csv
Summary information for studies in common-garden review
This file contains all the summary information from studies found in a literature search for common-garden or reciprocal-transplant experiments testing the hypothesis that there is a genetic basis to elevational or latitudinal variation in LMA, Nmass, or Narea within a species of plant. Column titles: STUDY NAME; author's last name and year published (see Appendix S2); Altitude common garden, whether the gradient is elevational; n. altitudes or latitudes, how many sites were sampled; Latitude common garden, whether the gradient is latitudinal; other, details if necessary; Trait(s), which traits were sampled; Genetic basis, whether statistically significant genetic basis was found; Effect size type, what statistical test/model was used; LMA, Nm, and Na, which of the 3 traits were sampled.
common_garden_review.csv
R functions to reproduce all analyses in paper
R file with all functions used in the accompanying R script file (see comments in body of file).
meta-analysis_functions.r
R scripts to reproduce all analyses in paper
R file that when run will reproduce all analyses in the paper, using functions in the accompanying file (see comments in body of file).
meta-analysis_scripts.r
README describing all accompanying files