Advantages of masting in the European beech: Timing of granivore satiation and benefits of seed caching support the predator dispersal hypothesis
The predator dispersal and predator satiation hypotheses provide alternative explanations for masting. Both assume satiation by seed-eating vertebrates. They differ in when satiation occurs: before or after seed removal and caching by granivores (predator satiation and predator dispersal, respectively). This difference is often overlooked, but it is demographically important because cached seeds are dispersed and often have a microsite advantage over non-dispersed seeds. We conducted rodent exclosure experiments in mast and non-mast years to test contrasting predictions of the predator dispersal and predator satiation hypotheses in our study system: yellow-necked mice (Apodemus flavicollis) interacting with European beech (Fagus sylvatica). Specifically, we tested whether: (1) removal of seeds from forest floor is similar during mast and non-mast years (i.e., lack of satiation before seed removal), (2) masting decreases removal of cached seeds (i.e., satiation after seed removal), and; (3) seed caching increases probability of seedling emergence relative to non-cached seeds.
1. Masting did not result in satiation of seed removal.
2. Masting decreased removal of cached seeds.
3. Seed caching dramatically increased the probability of seedling emergence relative to non-cached seeds.
European beech benefits from masting by scatterhoarder satiation that occurs only after seeds are removed and cached in suitable microsites. These findings do not exclude other evolutionary advantages of beech masting. However, they indicate that fitness benefits of masting range beyond the most commonly considered advantages of predator satiation and increased pollination efficiency.