The forest within the forest: restoration of Galapagos host-epiphyte networks.

Ecosystem restoration is increasingly implemented to mitigate biodiversity loss. Epiphytes represent up to a third of tropical plant diversity and perform key ecosystem functions. Yet, they are highly vulnerable to deforestation and their recovery under restoration remains understudied. We evaluated the effect of invasive plant removal on host-structurally dependent plant (SDP) interactions in the endemic and endangered Scalesia pedunculata forest on Santa Cruz Island (Galapagos). We considered the full assemblage of SDPs, including obligate, facultative, accidental epiphytes and other phorophyte-associated plants such as vines and lianas. Using 20 paired 10 × 10 m plots (invaded versus 11 years of restoration), we compared interaction network structure, SDP diversity and the main predictors of SDP richness. Network descriptors did not differ between treatments but restored plots supported higher richness. Richness per host increased with moss cover and host tree diameter (DBH) in sites under restoration, indicating improved host suitability. The endemic S. pedunculata was identified as a keystone host, with the highest species strength and degree. However, its lack of regeneration in invaded plots threatens long-term SDP persistence. Our findings demonstrate that restoration enhanced SDP richness by fostering suitable hosts, highlighting the relevance of integrating biotic interactions into restoration planning and monitoring.