Invasive predator reshapes island trophic network and biogeography

Invasive predators are causing rapid declines in global biodiversity, especially on islands, which may further cause irreversible ecological disruption and loss of ecosystem functions because of relatively simplified food webs. However, the cascade effects of invasive predators on the trophic network structure of islands and their relationships with island isolation and area remain poorly understood. Here, using intensive field surveys and fecal DNA metabarcoding data, we explore the effects of the invasion of a global frog predator, the American bullfrog (Aquarana catesbeiana), on native anuran-prey trophic networks across 64 invaded and control ponds spanning 21 islands in the Zhoushan Archipelago, China. We show that invasive bullfrogs destabilize the native anuran-prey network by replacing the central network positions originally occupied by native anurans, driving the generalization of natives' diets, increasing the native network connectance, decreasing the native network modularity, and diluting the effects of island isolation on the network structure metrics. These impacts are most significant on islands with long bullfrog invasion histories and those close to the mainland. Our results demonstrate how one invasive predator can reshape the native trophic network and its changes with island characteristics, potentially further homogenizing the unique functions and services of island ecosystems.