Climatic niche conservatism in non-native plants depends on introduction history and biogeographic context.

Niche conservatism is a fundamental assumption in predictive models for managing non-native species, but its generality remains debated due to mixed empirical evidence. We argue that this reflects underexplored context dependencies, as few studies have compared the niche dynamics of species introduced to multiple regions. Here, we quantify climatic niche changes in 1566 introductions of 316 non-native plant species across eight regions, including continents and archipelagos. While niche expansion into previously unoccupied conditions was low, niche conservatism and unfilling varied strongly across regions. Species with small native range sizes exhibited greater niche expansion. Longer residence times reduced niche unfilling, suggesting that a lack of niche conservatism observed in many regions might be transient and potentially linked to dispersal limitations. Our results highlight the necessity to consider region-specific contexts when assessing the potential for niche changes and provide a critical foundation for improving predictive models informing the management of non-native species.