Tracking individual seed fate confirms mainly antagonistic interactions between rodents and European beech.

Abstract

Food-hoarding granivores act as both predators and dispersers of plant seeds, resulting in facultative species interactions along a mutualism-antagonism continuum. The position along this continuum is determined by the positive and negative interactions that vary with the ratio between seed availability and animal abundance, particularly for mast-seeding species with interannual variation and spatial synchrony of seed production. Empirical data on the entire fate of seeds up to germination and the influence of rodents on seed survival is rare, resulting in a lack of consensus on their position along the mutualism-antagonism continuum. Here, we quantified annual seed rain and rodent abundance in an old-growth European beech forest and tracked 639 beechnuts to the seedling stage with 84% of seeds successfully located. Over 4 study years that covered the range of seed-to-rodent ratios, not a single seed successfully germinated after dispersal, illustrating a predominantly antagonistic interaction between rodents and seeds of European beech. Therefore, our findings do not support the predator dispersal hypothesis and partially contradict the predator satiation hypothesis, as the highest number of germinants and intact seeds were found in situ after an intermediate seed crop, not a bumper crop. Our results underline the necessity to track seeds up to germination.