Accepted Article ‘This article is protected by copyright. All rights reserved.’ Mimicking a rainfall gradient to test the role of soil microbiota for mediating plant species responses to drier conditions Michael J. O’Brien 1,2 , Francisco I. Pugnaire 1 , Susana Rodríguez-Echeverría 3 , José A. Morillo 1 , Francisco Martín-Usero 1 , Almudena López-Escoriza 1 , Diego J. Aránega 1 and Cristina Armas 1 1 Estación Experimental de Zonas Áridas, Consejo Superior de Investigaciones Científicas, Carretera de Sacramento s/n, ES-04120 La Cañada, Almería, Spain 2 URPP Global Change and Biodiversity, Univ. of Zurich, Zurich, Switzerland 3 Centre for Functional Ecology, Dept of Life Sciences, Univ. of Coimbra, Coimbra, Portugal Corresponding author: Michael J. O’Brien, Estación Experimental de Zonas Áridas, Consejo Superior de Investigaciones Científicas, Carretera de Sacramento s/n, ES-04120 La Cañada, Almería, Spain. Email: mikey.j.obrien@gmail.com Decision date: 19-Jun-2018 This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: [10.1111/oik.05443].