Resource subsidies mediated by non-native species: a review

Abstract

Non-native species are recognized as one of the major drivers of biodiversity change globally, with profound impacts on ecosystem functions and services. Despite the high number of studies on non-native species published, mainly in the last two decades, an often-overlooked aspect is their role as mediators of resource subsidies (the cross-boundary movement of energy, nutrients, or materials). This topic may have theoretical and empirical implications because non-native species may play a major role in ecosystem connectivity by transporting—or interrupting the transport of—energy and organic matter. Therefore, the main aims of this review were to (1) assess temporal trends, geographic distribution, and methodological approaches in research on resource subsidies mediated by non-native species; (2) synthesize how non-native species alter the magnitude, direction, and dynamics of resource subsidies across ecosystems and their implications for ecosystem functioning; and (3) identify key gaps in current knowledge and define future research priorities. The review retrieved 143 publications, resulting in 212 case studies, that collectively show that non-native species can both reduce and increase resource flows across ecosystem boundaries, with implications for ecosystem dynamics and connectivity. Although terrestrial and freshwater connectivity accounted for the majority of published case studies (56%), many ecosystem linkages remain underexplored. A significant geographic bias was found, with Africa being severely understudied (2.8% of all publications), followed by Asia (7.7% of all publications). Taxonomic representation was also skewed, with the majority of studies focusing on non-native plants (28.8% of case studies), non-native fish (25.5% of case studies), and mammals (21.7% of case studies), whereas fungi (0.9%) and bacteria (2.4%) were largely neglected despite their fundamental roles in decomposition processes. Key priorities for advancing this field include long-term monitoring, the application of emerging molecular and analytical tools (e.g., telemetry, eDNA, metabarcoding, and isotopic tracers), and the integration of artificial intelligence to synthesize large datasets. The findings provide the first synthesis of resource subsidies mediated by non-native species. This information is crucial for biodiversity conservation and the effective management of ecosystems and their connectivity.