Fine-scale spatiotemporal variation in seed-rodent interactions: A potential contribution to species coexistence

Abstract

Seed predation and dispersal by rodents plays an important role in seedling establishment and forest regeneration. Spatiotemporal variation in seed availability at fine scales is ubiquitous in the forest because of the different spatial locations and fruiting phenology among tree species, which may further lead to spatiotemporal variation in seed-rodent interactions. However, previous research has generally treated such variation as random effects among experimental replicates and provides few relevant explanations. Therefore, in this study, we directly tested the spatiotemporal variation in seed predation and dispersal at a fine-scale by manipulating a dynamic pattern of seed availability, releasing different species of seeds into the forest at 10 m intervals in space and 6 day intervals in time. In total, we tracked the dispersal and predation of 40,500 seeds belonging to 45 tree species in a subtropical forest in southwest China for three consecutive years. Our results provide strong evidence that fine-scale spatiotemporal variation in seed dispersal and predation by rodents always exists, although the overall intensity of seed harvest and removal significantly differs among experimental years and plots. Furthermore, the fine-scale spatiotemporal effect differs among plant species, indicating that the spatiotemporal effect may be species specific. Consequently, any specific seed may have the probability to survive or be dispersed as long as it appears at a specific site and time. Our findings further suggest that the fine-scale spatiotemporal variation in seed-rodent interactions may contribute to species coexistence in the forest, at least at the seed stage. Generally, we expect that similar fine-scale spatiotemporal variations occur in other plant-animal interactions, such as herbivory and pollination. Incorporating fine-scale spatiotemporal variation into future plant-animal studies may help us to gain a better understanding of species coexistence and biodiversity maintenance.