Dissecting the roles of seed nutrient content and coat thickness in seed dispersal and fate mediated by rodents: A field experiment using artificial seeds

Abstract

Seed traits such as nutrient content and coat thickness significantly influence the foraging behavior of scatter-hoarding rodents and the fate of plant seeds. However, isolating the effects of these traits is challenging due to their covariance. This study aims to disentangle these effects using artificial seeds with varying levels of coat thickness and nutrient content to simulate natural seeds in a subtropical forest ecosystem in the Dujiangyan region, China. These seeds were deployed in the field to assess rodent foraging behavior, including harvest preferences, likelihood of consumption, probability of scatter-hoarding, and dispersal distance. We found seed coat thickness and nutrient content independently influenced rodent foraging behavior. Thicker seed coats reduced harvest preferences and consumption likelihood, but increased the dispersal distance; the probability of scatter-hoarding was the highest for seeds with a medium-thick seed coat. Higher nutrient contents increased both harvest preferences and scatter-hoarding probability but reduced consumption likelihood. When both traits were considered together, an optimal trait combination emerged: seeds with medium coat thickness and higher nutrient content had a higher probability of being scatter-hoarded and longer dispersal distances. Our findings highlight the significant impact of seed coat thickness and nutrient content on seed fates and dispersal distance through their influence on rodent foraging behavior. This study provides a novel insight into the complex interactions between plants and animals, as well as offers vital evidence for understanding seed ecology and plant population dynamics in forest ecosystems.