Seasonality and morphological variation shape intraspecific seed dispersal networks in gopher tortoises

Intraspecific variation within animal seed disperser populations can influence the structure and function of plant-animal networks, with important consequences for vegetation dynamics and consumer behavior. However, such variation remains poorly studied. We used an individual-based bipartite network approach to examine how morphological traits (e.g., carapace size) and seasonality (wet vs. dry season) shape seed dispersal interactions of gopher tortoises (Gopherus polyphemus) inhabiting South Florida’s hyper-diverse pine rockland ecosystem. Over 1.5 years, we dissected fecal samples from 14 radio-tracked tortoises and identified seeds from 55 plant species. The annual tortoise–plant network was significantly modular and specialized but not nested, indicating that distinct subsets of tortoises and plants interacted more frequently with each other than expected by chance. Larger individuals were more generalized and dispersed a greater diversity of seeds than smaller tortoises. Seasonal subnetworks also displayed high modularity but differed markedly in structure, with 61% interaction dissimilarity driven primarily by interaction rewiring (89%) rather than species turnover. During the wet season, both tortoises and fleshy-fruited plant species exhibited reduced specialization and increased partner diversity, reflecting the influence of fruiting phenology on network structure. Together, our findings demonstrate that morphological variation and seasonal resource availability jointly shape seed dispersal networks. These results underscore the importance of preserving intraspecific variation in disperser populations and highlight the value of individual-based network analyses for understanding the ecological and evolutionary dynamics of seed dispersal under environmental change.