Ecological and human use traits shape lemur-tree interaction networks across human-modified landscapes

Functional traits drive species interactions that structure ecological communities around the world. Both ecological and human-use traits may be associated with the structure of ecological networks in human-modified systems. In secondary and primary forests in northeast Madagascar, we quantified the importance of lemur species and the tree genera they consume using network measures of centrality, determined the ecological trait predictors of tree centrality, and investigated the relationships between tree centrality and human use. Our study advances understanding of ecological interactions by: combining ethnobiological data with direct observations to reduce undersampling of cryptic interactions; using a bipartite network approach to understand the connections between land use types; investigating frugivory, seed predation, and herbivory interactions; and accounting for phylogenetic signal in tree centrality. Diurnal lemurs tended to be more central to primary forests, whereas nocturnal lemurs were more central to secondary forests. Tree centrality in primary forest networks was negatively associated with tree diameter, wood density, and endemism status. Network structure was related to human use traits in the secondary forest but not in primary forest; trees central to secondary forest networks were more likely to be used by people, especially in herbivory networks. Our results highlight the importance of combining research-based observations with ethnobiological data to advance our understanding of the trait-based functioning of ecological networks. Conservation approaches should be attentive to the implications of ecological interactions for both ecological functioning and human well-being.