Structure and Stability of Lemur‐Tree Ecological Networks Across Primary and Secondary Forests

ABSTRACT Forest degradation is disrupting species interactions, altering the structure and stability of ecological communities. Understanding the organization of species interactions across human‐modified landscapes is urgent in biodiverse areas experiencing major conservation threats, such as Madagascar. In both primary and secondary forests in northeast Madagascar, we investigated lemur‐tree network structure and stability. We combined ethnobiological data (interviews with 81 local knowledge holders) with direct observations during field work to construct ecological networks representing frugivory, herbivory, and seed predation. In a multilayer approach, we examined interactions both within and between forest types. We found that primary forest networks supported substantially higher interaction abundances, diversity, and evenness compared to secondary forest networks. There were also differences in structure across interaction types; for example, herbivory networks had a more modular structure than frugivory or seed predation networks. Simulated species extirpation showed that primary forests were more stable to perturbations than secondary forests or multilayer systems, even after accounting for how lemurs likely adjust their diets as plants go locally extinct (i.e., interaction rewiring). While seven lemur species connected primary and secondary forests, multilayer networks were consistently less stable than single‐layer networks, emphasizing the likely vulnerability of human‐modified landscapes to environmental change and the ecological importance of species that connect the primary and secondary forest networks.