Abstract
Invasive plants are expanding their geographical distribution across new regions. Expansion modeling is crucial for geographic prioritization in management policies. However, the assumption of niche conservatism and the lack of information of the species physiological response to the environmental factors determining species presence may hinder predictions. In this study, we aimed to understand the expansion of the widely distributed plant Carpobrotus edulis in Europe. We contrasted introduced and native C. edulis ecological niches and explored the experimental response to temperature, a major determining factor for species distribution, of native and invasive individuals in terms of different biochemical markers. Niche analysis revealed an expansion of the introduced niche to occupy colder climates. Introduced and native individuals showed differential mechanisms facing low temperatures. Individuals from the native range showed an increased sensitivity to chilling, as reflected by photosynthetic pigment degradation, increased de-epoxidation of xanthophylls and the accumulation of the lipophilic antioxidant alpha-tocopherol. The found physiological differentiation towards an increased invasive chilling tolerance of invasive C. edulis individuals together with a high propagule pressure may explain the introduced climatic niche shift to colder climates observed, allowing the extensive expansion of this species in Europe.