Mucilage secretion by seeds doubles the chance to escape removal by ants

9 páginas, 3 figuras.-- Título en el preprint: Post-dispersal seed anchorage to soil in semiarid plant communities, a test of the hypothesis of Ellner and ShmidaPost-dispersal seed predation is a risk for plants in semiarid environments, leading to strategies to protect their propagules from seed collection by animals. In this study, we evaluated the importance of mucilage secretion in seeds as a mechanism to reduce seed collection by ants. We selected three Mediterranean species with strong mucilage secretion on their seeds which become sticky upon wetting. Seeds of Rosmarinus officinalis, Fumana ericoides, and Fumana thymifolia were exposed to ants and survival was compared between dry loose seeds and seeds glued to the soil with previously secreted mucilage. The study site was in the Sierra Calderona, 25 km north of Valencia (Spain). The ant-plant interaction was analyzed by scrutinizing seed collection by ants and by analyzing the waste piles of ant nests. To test survival, groups of 10 seeds were placed on the ground. Each group consisted of five control (dry) and five mucilaginous seeds (previously mucilage secreted) and was covered by the cover of a Petri dish modified to permit only the entry of ants. Seeds were inspected weekly for seed disappearance and the survival function (Kaplan-Meier estimator) was calculated. Seeds of the target species were important food items for ants and were actively collected, and more than 50 % of the experimental seeds that were glued to the ground with their own mucilage survived at the end of the study period but only 0-20 % of the control seeds survived after the same time of exposure. The implications for plant establishment of these findings are discussed.This research was supported by the Spanish "Plan Nacional de I + D + I" projects CGL2005-03912 (ARIDERO) and CGL2009-07262 (ROSMARINUS)]. We would especially like to thank Xavier Espadaler for his identification of the ant species and Cristian Escrihuela for his continuous help in the laboratory and in the field. Also we would like to thank Santiago Donat, Svenja Stadtschreiber, and Mechtild Engelbrecht for their assistance in the field and to two anonymous reviewers for their comments that greatly improved the manuscript. Meike Engelbrecht enjoyed a grant from the Spanish National Research Council (CSIC) [JAE-Pre 08 00758]. The National Meteorological Agency of Spain kindly provided the precipitation data of the 1990–2011 periods.Peer reviewe