Resource subsidies mediated by non-native species: a review

Non-native species are recognized as one of the major drivers of biodiversity change globally, having profound impacts on ecosystem functioning and affecting the provision of key ecosystem services. Despite the high number of studies on non-native species produced, mainly in the last two decades, one often overlooked aspect is their role as mediators of resource subsidies (i.e. cross-boundary movement of energy, nutrients, or materials). This topic may have theoretical and empirical applications since non-native species may play a major role in the connectivity of habitats transporting (or interrupting the transport of) energy and organic matter. Therefore, the main aims of this review were to (1) recognise main spatial, temporal, and taxonomic patterns and gaps in knowledge, (2) better understand how non-native species influence resource subsidies and their possible implications for ecosystem dynamics, and (3) identify future research avenues. Our review retrieved a total of 143 publications that matched our keyword search, resulting in a total of 212 case studies. These studies collectively show that non-native species can both disrupt and facilitate resource flows across ecosystem boundaries, with implications for ecosystem dynamics and connectivity. While terrestrial and freshwater connectivity accounted for the majority of published case studies (54%), many ecosystem linkages remain underexplored. A significant geographical 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 fish (25.5% of case studies) and mammals (21.7% of case studies), while important organisms such as fungi (0.9%) and bacteria (2.4%) were largely neglected, despite their fundamental role in decomposition processes. We identify key priorities for advancing this field, including long-term monitoring, the application of emerging molecular and analytical tools (e.g. telemetry, eDNA, metabarcoding, isotopic tracers), and the integration of artificial intelligence to synthesize large datasets. Our findings provide the first quantitative synthesis of resource subsidies mediated by non-native species, this information being crucial for biodiversity conservation and the effective management of ecosystems and their connectivity.