Moms are better nurses than dads: gender biased self-facilitation in a dioecious Juniperus tree

10 páginas, 4 figuras, 2 tablas.Questions: Can gender of nurse plants affect regeneration patterns and spatial population structure? Is there a seedseedling conflict in the regeneration process? What factors are responsible for the clumped spatial population structure observed for adult trees?Location: Mediterranean cold semi-arid high mountains in Spain.Methods: The spatial pattern of adult Juniperus thurifera trees was studied by means of Ripleyʼs K-analysis. χ2 analyses were used to test for natural seedling frequency in each of three main microhabitats: (1) under female and (2) male tree canopies and (3) in open interspaces. The observed pattern was explained experimentally by studying seed and seedling survival for two years. Survival probabilities were calculated across life stages for each of three main microhabitats.Results: Adult J. thurifera trees were aggregated in space. Most seedlings were found underneath female J. thurifera trees. Experimental studies demonstrated that from seed dispersal to seedling survival all life stages showed the same positive or negative trend within a given microhabitat, indicating stage coupling and no seed-seedling conflicts. Attraction of frugivorous birds by reproductive female junipers and improvement of environmental conditions beneath tree canopies were the main factors responsible for the variation in seedling density among microhabitats; highest underneath female trees and lowest in open interspaces.Conclusions: In dioecious species, the gender of nurse plants can significantly determine the spatial population structure. In J. thurifera forests, facilitation beneath female trees occurs among all life stages without any sign of seed-seedling conflict. The most critical factors shaping the spatial population structure were directed seed dispersal and environmental amelioration beneath female conspecific trees.We wish to thank Rune Økland, Ragan Callaway, Eugene Schupp and Alfonso Valiente-Banuet for their revision of the manuscript. Thanks also to the inhabitants of the mountains for their hospitality: “Gracias a todos los habitantes de la Puebla de San Miguel, a su Alcalde, Luis María Alcusa, a Jesus Monedero, de la Guardería Forestal y a la brigada de IMELSA, especialmente a Paco, por su ayuda y atenciones durante la realización de este trabajo. Gracias también a Emilio Laguna, Amparo Olivares, Vicente del Toro, Paco, y el resto de la Brigada de las Microrreservas de Flora por su ayuda con las vallas de exclusión del ganado”. Thanks for their help and support to the Llavoratori: Tono Bellido, Jorge Sellés, Gabriela Gleiser, Jaume Tormo and Esther Bochet. This work was funded by the Spanish Ministerio de Educación y Ciencia (AGL2001-1061). Daniel Montesinos enjoyed a grant (BES-2002-1828) from the MEC.Peer reviewe