Abstract
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.