Consistencies in post-dispersal seed predation of temperate fleshy-fruited species among seasons, years and sites

1. Seed predation of 12 fleshy-fruited species was recorded in experimental dishes under early successional forest in south-west Germany (four seasons 1992 and 1993) and in south England (summer 1995). On each occasion, 200 dishes were laid out, each containing five seeds of a given species. The mean time for three or more seeds to be removed was taken as a measure of granivore preferences. We tested correlations of these preferences with several physical and nutritional seed traits.
2. Live trapping and selectively accessible dishes indicated that rodents were the major granivores ( Apodemus sylvaticus, Apodemus flavicollis, Clethrionomys glareolus ); no predation by birds or insects was observed. The rank order of the rodents' seed preferences was consistent among sites, seasons and years, but mean predation differed between species, sites and seasons. Seed predation was highest in summer and lowest in winter. Possible implications of the seasonal pattern in predation risk are discussed.
3. The preferences of rodents were significantly correlated with the species-specific viability of seeds (i.e. percentage of sound seed) in five of eight experiments and with the percentage of water in the embryo-plus-endosperm fraction (EEF) in four of eight experiments. Surprisingly, preferences were not correlated to seed mass, EEF mass or nitrogen concentration. Predation was lowest among toxic species ( Berberis vulgaris, Euonymus europaeus, Sambucus nigra ) and among species with woody endocarps ( Cornus sanguinea, Crataegus spp.).