Structure and stability of lemur-tree ecological networks across primary and secondary forests
Forest degradation alters species interactions, yet its effects on ecological network stability remain understudied in biodiversity hotspots. Using interviews with 81 local knowledge holders and field observations, this study mapped frugivory, herbivory and seed‑predation networks between lemurs and plants in primary and secondary forests of northeast Madagascar. Primary forests supported far greater interaction abundance, diversity and evenness, and were more resilient to simulated species loss—even when accounting for dietary rewiring. Herbivory networks were more modular, and seven lemur species linked forest types, yet multilayer networks were consistently less stable. Results underscore the ecological importance of intact primary forests and the heightened vulnerability of human‑modified landscapes.
Subject Tags
- Forest
- Biodiversity
- Wildlife
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.
Citation
DeSisto, C. M., Bezaralahy, R., Dimbiarijaonina, C., Emerancine, R., Feno, T., Mahazandry, E., ... & Herrera, J. P. (2025). Structure and Stability of Lemur‐Tree Ecological Networks Across Primary and Secondary Forests. Biotropica, 57(6), e70109. https://doi.org/10.1111/btp.70109
TNC Authors
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John R. Poulsen
Global Director of Science Capacity/Deputy Director of One Conservancy Science
The Nature Conservancy
Email: john.poulsen@tnc.org