Climate space, traits, and the spread of nonnative plants in North America

The future distribution of invading species depends on the climate space available and certain life history traits that facilitate invasion. Here, to predict the spread potential of plant species introduced in North America north of Mexico (NAM), we compiled distribution and life history data (i.e., seed size, life form, and photosynthetic pathways) for 3021 exotic plant species introduced to NAM. We comparatively examined the species' range size and climate space in both native and exotic regions and the role of key life history traits. We found that large climate space for most exotic plants is still available in NAM. The range sizes in global exotic regions could better predict the current range sizes in NAM than those in global native regions or global native plus exotic regions. C3 species had larger ranges on average than C4 and CAM plants, and herbaceous species consistently showed stronger relationships in range size between native and exotic regions than woody species, as was the case within the C3 species group. Seed size was negatively related to range size both in native regions and in NAM. However, seed size surprisingly showed a positive correlation with global exotic range size and no correlation with the current actual global (native plus exotic) range size. Our findings underline the importance of species' native distribution and life history traits in predicting the spread of exotic species. Future studies should continue to identify potential climate space and use underappreciated species traits to better predict species invasions under changing climate.