Anthropogenic and environmental factors are associated with frugivore interaction diversity

Species interactions are a key component of biodiversity; frugivore interactions drive tree population dynamics and landscape connectivity, especially in tropical forests. Here, we quantify the effects of anthropogenic factors on interaction diversity in forests across Gabon, accounting for natural environmental variation. Using data from 252 1-ha botanical plots and frugivory interaction data among 153 frugivore species with distributions in Gabon, we (i) assess the relationship between frugivory syndrome—i.e., whether or not a tree has fruits that are consumed by animals—and contribution to tree taxonomic and phylogenetic β diversity, (ii) quantify the effects of environmental variables on interaction diversity, and (iii) investigate anthropogenic effects as drivers of frugivory syndrome, as well as the richness, α diversity, local contribution to β diversity, and evolutionary distinctiveness of interactions. Frugivore interactions were predominant across Gabon; 84%–85% of individual trees were frugivore trees. Frugivore trees made greater contributions to tree β diversity across Gabon than trees without frugivore interactions, suggesting the importance of frugivory for maintaining regional biodiversity through seed dispersal services. Anthropogenic effects were associated with interaction richness, α diversity, and β diversity, but not evolutionary distinctiveness. While forest plots in areas of higher population density tended to have lower interaction richness and α diversity, they tended to make more contributions to national β diversity. However, the opposite was true for plots closer to villages. Overall, our findings provide new insights into the role of humans in frugivore interaction diversity; different anthropogenic effects have varied and nuanced impacts on interaction diversity. • Approximately 85% of trees across Gabon were frugivore-dispersed. • Trees consumed by frugivores contributed more to national β diversity. • Population density was associated with lower interaction α diversity but greater β diversity. • Plots closer to villages had greater interaction α diversity but lower β diversity.