Deconstructing niche shifts: Using native and non-native records to assess the invasion potential of geographically constrained species

Geographically-constrained species typically occupy small climatic niches in their native range, and are therefore often assumed to pose a low risk of becoming invasive. However, the association between range size and climatic niche is correlative, and the cause of the constraint, whether it is physiological limits, competition, or dispersal limitations, impacts their risk of becoming invasive. We investigated the interplay between geographic range and niche breadth for the South American tree species Tipuana tipu (Fabaceae), and quantified how the spatial projection of the realised niche may be impacted by this relationship. We constructed a global dataset of location records, including datasets of both non-native and cultivated plants. We constructed a correlative species distribution model (CLIMEX Match Climates), and used ExDet and Ecospat to investigate and characterise niche shift. We found that T. tipu had a large climatic niche, despite having a small geographic native range. Projecting the correlative model indicated a large proportion of Australia and the globe were climatically suitable for T. tipu . Moderate niche shift occurred in all introduced regions, with a significantly greater niche shift amongst datasets of cultivated plants. Geographically-constrained species may have large climatic niches, thereby posing an unanticipated invasion risk in their non-native range. Correlative modelling is a useful tool for modelling species distribution; however, a small geographic range does not guarantee a small climatic niche. Niche shifting may also affect correlative modelling results and their interpretation. • Species with small geographic native ranges may have large climatic niches. • Invasion risk for species with small geographic ranges may be greater than assumed. • Cultivated plant records can be an important source of ecological information. • Niche shift was greater for cultivated plants than for naturalised plants. • Niche shifting affects correlative modelling results and their interpretation.