Plant-plant interactions are a major mechanism governing plant communities and their responses to environmental changes. However, it remains unclear how phylogenetic similarity affects interactions and how they influence the resulting community structure. Thus, our aim with this Thesis was to clarify fundamental aspects of plant interaction, their dependence on phylogenetic similarity, and the consequences for the dynamics of communities. We wanted to test i) whether there are complementary effects of foundation species increasing species richness and phylogenetic diversity; ii) if phylogenetic similarity among species influences plant interactions; iii) how these interactions change along an environmental severity gradient; iv) whether phenotypic variability in a foundation species modulates species richness and phylogenetic diversity, and whether it affects facilitation costs; and finally, under homogeneous environmental conditions, v) we expect ontogenetic shifts towards more negative species interactions for closely related species and towards less negative interactions for distantly related species. For these purposes we made various observations and experiments in the field supported by a series of physiological and functional analyses of plant communities.

Este trabajo ha sido posible gracias a la concesión de una beca predoctoral para el desarrollo de tesis doctorales en el marco del Programa “Junta de Ampliación de Estudios” (JAEPre_2010_01004) y ha sido desarrollada en la Estación Experimental de Zonas Áridas en Almería, instituto perteneciente al Consejo Superior de Investigaciones Científicas (EEZA-CSIC). Además, el proyecto OAPN (002/2009) financiado por el Organismo Autónomo de Parques Nacionales, Ministerio de Medio Ambiente y Medio Rural y Marino, ha contribuido al desarrollo de esta tesis.

Peer reviewed