How seed defense and seed abundance predict dispersal and survival patterns in Camellia.

Abstract

Little is known about how seed defense and seed abundance interact with behavioral responses of seed dispersers to predict dispersal and survival dynamics in animal-dispersed plants. By tracking the fate of individual seeds in Camellia stands with high and low seed abundance in Southwest China in 2007, we investigated the dispersal and survival of 2 high-saponin Camellia species (Camellia oleifera and Camellia sinensis and 1 non-saponin species (peanut Arachis hypogaea) as a control. Saponins in Camellia seeds are chemical compounds that act as seed defense. Our results were most consistent with the predictions based on the predator satiation hypothesis and the plant defense hypothesis. At the abundant Camellia stand (predators and dispersers were satiated), more Camellia seeds survived at the source but fewer were hoarded and survived at cache sites. At the sparse Camellia stand (predators and dispersers were not satiated), no Camellia seeds survived at the source, but more Camellia seeds were hoarded and survived at cache sites. Unlike Camellia seeds, no peanuts survived at the source at both stands, while more peanuts were hoarded and then survived at cache sites in the abundant Camellia stand compared to none at the sparse Camellia stand. In addition, the 2 Camellia species showed similar trends for seed fates across different dispersal stages. Our study indicates that the combined effects of seed abundance and seed defense, compared to their separate effects, provide a more accurate prediction for dispersal and survival patterns in animal-dispersed Camellia species.