Non-Native Plants Alter Bird-Plant Frugivory Network Structure in a Human-Modified Tropical Landscape

Frugivory interactions are key plant-animal mutualisms that facilitate seed dispersal and promote ecosystem resilience. However, these interaction networks are increasingly altered by the widespread introduction of non-native plants through human activities. The integration of such species into frugivory networks-and their consequences for network stability-remains poorly understood. Here, we examined the role of non-native plants in shaping frugivory network structure and robustness in a human-modified tropical landscape. Using DNA metabarcoding of faecal samples from 21 frugivorous bird species in Gamboa, Panama, we identified consumed plant species and quantified the contribution of non-natives to avian diets. Non-native plants significantly altered network structure, reducing nestedness while increasing connectance and modularity compared to native-only networks. Extinction simulations revealed that non-native plants, despite comprising only 28% of plant species, triggered disproportionately higher secondary bird extinctions. Yet, these species showed lower persistence during sequential bird removals, creating a paradox: they act as crucial connectors within the network while simultaneously undermining its stability. Notably, three non-native species served as key connector species linking network modules. The high connectivity of certain non-native connector species is particularly concerning given their documented invasive potential in other regions. We anticipate that these findings will inform conservation strategies in human-modified landscapes, particularly regarding the monitoring and management of highly connected non-native plants that may both compromise ecosystem stability and facilitate biological invasions. While non-native plants may provide temporary alternative food resources for adaptable frugivorous birds navigating increasingly human-modified environments, they simultaneously risk diverting seed dispersers from native plants and undermining long-term ecosystem integrity.