Divergent temporal dynamics of native and non‐native insular arthropods in fragmented forests

Non-native species introductions have caused biodiversity loss worldwide, yet it is unclear how temporal diversity patterns vary across native and non-native communities, and what mechanisms control their respective dynamics and assembly. Using a unique 12-year time series dataset of arthropods sampled in forest fragments on Terceira Island, we observed no systematic species losses but steady temporal β-diversity (Sørensen dissimilarity based on species presence-absence) for non-native, native endemic, and native non-endemic assemblages. However, native endemics and non-endemics showed an overall increasing trend in Bray-Curtis dissimilarity (incorporating species abundances), with many previously abundant native species becoming progressively rarer. By constructing neutral models, we accurately predicted temporal diversity patterns for non-natives but not for native endemics and non-endemics, displaying their divergent temporal dynamics. These results indicate that non-native assemblages are more consistent with stochastic source-sink mass effect dynamics, while neutral drift interacting with non-natives and/or environmental changes might drive native assemblage dynamics.