Allochthonous resources are less important for faunal communities on highly productive, small tropical islands

Ecosystems are interconnected by energy fluxes that provide resources for the inhabiting organisms along the transition zone. Especially where in-situ production is low, ecosystems can become highly dependent on external resources. The dependency on external input becomes less pronounced in systems with elevated in-situ production, where only consumer species close to the site of external input remain subsidized, whereas species distant to the input site rely on the in-situ production of the ecosystem. It is largely unclear though if this pattern is consistent over different consumer species and trophic levels in one ecosystem, and whether consumer species that occur both proximate to and at a distance from the input site differ in their dependency on external resource inputs between sites. Using stable isotope analysis, we investigated the dependency on external marine input for common ground-associated consumer taxa on small tropical islands with high in-situ production. We show that ...