Functional traits determine formation of mutualism and predation interactions in seed-rodent dispersal system of a subtropical forest

• Seeds and rodents show convergent or divergent formation of mutualism and predation interactions.
• Seeds with high handling and nutrition traits show high mutualism but low predation with both rat and mouse species.
• Seeds with high tannin trait show high mutualism but low predation with mouse species.
• Anti-predation seed traits increase mutualism suggesting formation of mutualisms may be closely related to predations.
• The handling time hypothesis, high tannin hypothesis, and high nutritional hypothesis were supported in some, but not all.

Network structure in plant-animal systems has been widely investigated but the roles of functional traits of plants and animals in formation of mutualism and predation interactions and community structure are still not fully understood. In this study, we quantitatively assessed interaction strength of mutualism and predation between 5 tree species and 7 rodent species by using semi-natural enclosures in a subtropical forest in southwest China. Seeds with high handling-time and nutrition traits (for both rat and mouse species) or high tannin trait (for mouse species) show high mutualism but low predation with rodents; while seeds with low handling-time and low nutrition traits show high predation but low mutualism with rodents. Large-sized rat species are more linked to seeds with high handling-time and high nutrition traits, while small-sized mouse species are more connected with seeds with low handling-time, low nutrition value and high tannin traits. Anti-predation seed traits tend to increase chance of mutualism instead of reducing predation by rodents, suggesting formation of mutualism may be connected with that of predation. Our study demonstrates that seed and animal traits play significant roles in the formation of mutualism and predation and network structure of the seed-rodent dispersal system.