“…After the first observations that the recruitment of many species in arid environments was favoured by a shaded microenvironment located under the canopy of shrubs (Niering, Whittaker, & Lowe, 1963;Shreve, 1931), many studies have confirmed the relevance of facilitation (Flores & Jurado, 2003), and its prevalence has been confirmed at different ecological scales (see reviews by Brooker et al, 2007;Callaway, 2007). On the other hand, the importance of competition in structuring vegetation in arid environments has generated a substantial amount of work suggesting that in these unproductive environments, plants compete intensely for the most limiting resource, water (see reviews by Fowler, 1986;Goldberg & Barton, 1992), yet have evolved morphological, physiological and demographic mechanisms that allow them to coexist (Cázares-Martínez, Montaña, & Franco, 2010;Ferrer, Montaña, & Franco, 2015;Goldberg & Novoplansky, 1997;Nobel, 1997;Schwinning & Ehleringer, 2001;Silvertown, 2004;Verhulst, Montaña, Mandujano, & Franco, 2008).…”