CONICET | Buscador de Institutos y Recursos Humanos

Pre-dispersal filters imposed on the seed stage can alter the likelihood of seed dispersal. We evaluate pre-dispersal seed loss due to predation by insects and abortion in Prosopis flexuosa and P. chilensis. This studywas conducted in two protected areas in the Monte Desert. We collected P. flexuosa and P. chilensis fruits from different trees, from two plots and two years. Samples were maintained for 50 days in translucent PVC boles stored in a laboratory under stable temperature (25 °C) and natural photoperiod, awaiting the emergence of insects. Then we opened the fruits and individually examined all seeds to determine their condition. We found that total pre-dispersal seed loss was 32% in P. flexuosa and 21% in P. chilensis. Seed predation by insects was the major source of pre-dispersal seed loss (19% in P. flexuosa and 14% in P. chilensis). The main seed predator was the apionid weevil (Brentidae: Apioninae) in P. flexuosa, and bruchid beetles (Chrysomelidae: Bruchinae) in P. chilensis. Some bruchid beetles prey upon seeds, completing their life cycle, whereas others remain inside seeds (41% in P. flexuosa and 49% in P. chilensis, of total seed damaged by bruchid beetles). Seed abortion wasanother important source of seed loss, especially for P. flexuosa, but its cause still remains unknown. We show and discuss the extent of a proposed methodology to account for pre-dispersal seed predation that includes the immature stages of non-emergent bruchid. Pre-dispersal seed loss by insects and abortion represent an ecological filter that limits the amount of seeds available for dispersal and establishment of these species. Understanding seed loss process may contribute to know and predict Prosopis population dynamics, revealing the natural regeneration mechanisms to forest recovery.