Table 2.

Summary of the standardized total effects on plant-plant interactions (sum of direct + indirect effects, standardized from 0-1) for the Structural Equation Models performed for the ten regions surveyed. Two different sets of models were performed: 1) those only including aridity and plant height as indicators of environmental conditions and plant traits, respectively (“common structure”), 2) those models including more environmental variables and traits to maximize the amount of variance explained (“model maximum R²”). PhyDis = evolutionary relatedness between interacting plants; Height = facilitated plant height; R² = amount of variance explained in the number of individuals/plant-plant interaction metric (the latter in bold); Envir = variable(s) indicative of environmental conditions (* = only aridity, † = only fertility, ‡ = aridity + fertility), Traits = facilitated plant height and specific leaf area (height and NMDS axis in the case of Venezuela).

Regional groups	common structure				model maximum R2
	Aridity	PhyDis	Height	R2	Envir	PhyDis	Traits	R2
Chile	−0.30	0.07	0.11	0.15/0.41	−0.30*	0.07	0.11	0.15/0.41
Ecuador	−0.03	−0.07	−0.05	0.02/0.11	−0.03*	−0.07	−0.05	0.02/0.11
Peru	0.29	0.11	0.24	0.05/0.38	0.29*	0.11	0.24	0.05/0.38
USA	−0.09	0.04	0.33	0.15/0.37	−0.09*	0.04	0.33	0.15/0.37
Venezuela	0.20	0.21	0.07	0.21/0.12	0.20‡	0.22	0.11	0.22/0.15
Australia (shrubs as nurses)	0.01	0.21	−0.14	0.07/0.08	−0.03*	0.20	0.23	0.16/0.18
Australia (trees as nurses)	−0.22	−0.19	0.32	0.00/0.21	0.24†	−0.20	0.31	0.06/0.25
Mediterranean (Spain, Morocco and Tunisia)	−0.05	−0.19	0.31	0.03/0.11	−0.07†	−0.19	0.31	0.02/0.20
Spain (sprouting shrubs)	0.04	0.07	0.10	0.02/0.12	0.06‡	0.07	0.27	0.01/0.19
Spain (non-sprouting shrubs)	−0.10	−0.02	0.04	0.06/0.07	−0.11‡	−0.01	0.17	0.08/0.08