The onset of precipitation mediates plant-avian disperser interaction in recalcitrant seeds: the case of Cryptocarya alba (MOL) Looser, in Mediterranean ecosystems, Central Chile

Background: Arid and semi-arid environments impose limitations on plant regeneration. This is especially important during biotic dispersal in plants with recalcitrant seeds, in relation to when and where birds disperse these seeds. Aims: We examined the effect of the onset of seasonal precipitation on the regeneration of Cryptocarya alba (Lauraceae), comparing seedling recruitment during early and late onset of precipitations. Methods: We conducted field experiments using bird-dispersed and gravity-dispersed seeds; half of the seeds were placed during the initiation of precipitations; the other half was kept, then was placed in the forest ground 2 months later. We compared seedling recruitment probability among treatments. Results: Seedling recruitment was positively affected by avian dispersal. Seedling recruitment was significantly increased only for the fraction of bird-dispersed seeds that matched with the beginning of precipitations. Conclusions: The ecological context as well as seed recalcitrance are critical in determining the fate of bird-dispersed seeds. Although this trait may be not adaptive in seasonal ecosystems, it is correlated with other traits that are adaptive (seed size, directed dispersal, spread of the dispersal season), thus explaining the persistence of species with recalcitrant seeds in such environments.