Insect seed-predator networks respond positively to restoration on a tropical island

Abstract

[eng] When non-native species invade ecosystems, coevolved plant–animal interactions and associated ecological functions are altered, often to the detriment of local biodiversity. While mutualistic interactions can benefit from—and assist with—ecological restoration through the removal of non-native species, community-level changes in antagonistic interactions due to restoration are less well understood. Insect seed predators provide important ecosystem functions, but can also have antagonistic effects through pre-dispersal seed predation which can cause fruit abortion or premature fruit drop, potentially affecting plant community composition.</p><p>2. Here, we used a network approach and data on trophic interactions from a large-scale field experiment to investigate the differences in insect seed predator communities between native restored sites (where non-native plants were removed) and unrestored sites dominated by non-native plants on the island of Mahé, Seychelles.</p><p>3. Restored sites contained more individuals and species of seed predators (up by 81% and 50% respectively), and experienced a greater predation intensity (1.06 ± 0.53 vs. 0.27 ± 0.09), and predator specialisation compared to unrestored sites. The proportion of predated samples was similar between treatments (~14%). Beta diversity, measured as species and interaction turnover, increased at restored sites.</p><p>4. Synthesis and applications: Our findings imply that vegetation restoration generates marked biodiversity benefits on native seed predator communities and their interactions. However, removing non-native plants did not result in the elimination of non-native seed predators, which might require targeted control measures. Our results highlight the importance of considering the effects of restoration on antagonistic interactions, in addition to those reported for pollination and seed dispersal services. Management practices should aim to control plant invasions for the conservation of native plant communities that serve as resources and refugia both for mutualists (e.g., seed dispersers and pollinators) and native insect seed-predator antagonists, both of which benefit native ecosystem function.