Unpacking the drivers of gut-passage times of seeds dispersed by frugivorous lemurs

Abstract

The impacts of endozoochory on plant populations are primarily determined by how seeds are processed in animal guts. Therefore, understanding the factors that determine how long seeds remain in the gut is crucial for predicting the outcomes of animal-mediated seed dispersal. We sought to provide a comprehensive understanding of the factors that may influence gut-passage times of endozoochorous seeds by (1) examining the extent of interspecific variation in gut-passage times across a diverse range of plant species and among a frugivore assemblage, (2) investigating the mechanistic drivers that may influence these gut-passage times of endozoochorous seeds, specifically focusing on the influence of seed and fruit traits, consumption of leaves following seed ingestion to dispersal, and animal activity patterns, and (3) exploring the degree of intraspecific variation to determine how gut-passage times fluctuate within species. We used data from direct observations of the interactions of three frugivorous lemur species with their food plants (81 species) over approximately 3 years, along with the traits of the plant community they dispersed. We found interspecific variations in seed gut-passage times for both lemur and plant species. Also, we found that fruit protein content, leaf consumption after eating fruits, and high levels of inactivity were positively associated with seed gut-passage time. In contrast, the fiber and fat content of fruits and the proportion of feeding times had a negative influence, while seed size and fruit sugar showed no significant effects. Additionally, our data show significant intraspecific variations in gut-passage times among different individual plants of the same species; however, we did not find significant differences in gut-passage times between male and female lemurs. These results provide compelling evidence of the significance of both plant and frugivore traits in shaping seed gut-passage times. They also highlight the importance of considering both intra- and interspecific differences in seed dispersal studies and the broader implications of endozoochory for plant population dynamics.