Invasion risk of the pond slider turtle is underestimated when niche expansion occurs

In recent years, changes have been detected in the climatic niches of several non-native species. In spite of this, and although Ecological Niche Models (ENMs) assume species show climatic niche conservatism, most studies still use ENM to assess the risks of invasion by alien species. In this study, we tested how niche expansion of the pond slider (Trachemys scripta) differs in invaded continents and how the performance of ENMs is affected by different niche shift scenarios. We described niche equivalence (whether native and invaded niches are identical), unfilling (native niche not present in invasive niche), expansion (invasive niche not present in native niche) and stability, based on the pond slider native and invaded occurrence points. We created an ENM using a Maxent method, based on the native occurrences of this turtle, and evaluated the model's performance using invasive records. Our results indicate that the pond slider niche changed when new areas that were either warmer (Asia and Latin America) or colder (Europe) than its native niche were invaded. Processes related to niche shift (stability, unfilling, and expansion) varied between continents. We also found that niche expansion is not a good predictor of ENM performance, which may indicate that the effects of this process on model performance are more complex than a simple direct effect. Finally, ENMs had especially poor performance when evaluated for sensitivity (percentage of presence records correctly predicted as presences in the models), reiterating the problems of using ENMs and their traditional evaluation methods when focal species do not conserve their native niche. We draw attention to important mitigatory measures, such as environmental education and strong control of trade to manage invasion by the pond slider turtle, since we still lack standard methods to predict the potential invasion risks for new areas when focal species do not conserve their native niche.