Large-scale facilitative effects of Vachellia caven

The importance of nurse plants structuring plant communities is well appreciated at local scales, yet the effect of a single nurse on large scales has been neglected in analyses. So far, studies only use environmental gradients within one type of ecosystem and tend to generalize the nurse effects. To assess how the effect of a single nurse species is modulated by different environmental settings, interactions between the shrub Vachellia caven and the surrounding plant communities were evaluated at 481 paired plots (outside vs underneath the plant crown), in 39 sites across two distribution ranges, the Mediterranean west and the mostly subtropical east of the Andes mountains (covering ca. 2x10 6 km2). Cover, abundance, and richness of perennial plants underneath and outside V. caven were used as response variables to estimate an index indicative of plant interactions (RII) and tested how this was affected by the rainfall gradient and distribution range.
Overall, RII responses to rainfall..., , , # Large-scale facilitative effects of *Vachellia caven*

## Description of the data and file structure

Three datasets are included.

The first file (**RII Data.csv**) corresponds to the RII data, including the three RII variables (cover, richness, and abundance) and rainfall, for each contrast, site, and range.

1. RII variables are measured with the Relative Interaction Index (Armas et al., 2004)*, which varies between -1 and 1, with values >0 expressing positive interactions, and values <0 negative interactions. In this data, indicate the effect of comparing underneath versus outside V. caven conditions using each of the raw variables (cover, richness and abundance)
2. Range and site are categorical variables, indicating the side of the distribution range and the specific sampling location, respectively.
3. Contrast is a categorical variable, indicating the ID of the contrast sampled (underneath versus outside V. caven conditions).
4. Rainfall is measured in mm

The secon...