Extinction risk from climate change is assessed using models of how species’ distributions will respond to climatic changes overtime. An assumption of this approach is that the current climatic conditions that species experience are the only ones they can tolerate. By comparing species’ native and naturalized ranges, i.e. those places where species are not native, but have been introduced and subsequently formed self-sustaining populations, it is possible to directly test whether a species’ historical distribution represents the complete suite of climatic conditions it can tolerate. We combined county-level climate data for the contiguous USA from the IWMI Climate Atlas with distribution data from BONAP for 204 woody plant species that are native the USA, but have naturalized populations beyond their native range boundaries within the U.S. We used these data to characterize the climate conditions characterizing the native and naturalized ranges of these species. In this study we assessed the ability of species’ characteristics (e.g. range size, dispersal ability) to predict when these mismatches will occur between the climatic conditions species' experience in their current range and the conditions they can actually tolerate.
Results/Conclusions
Seventy-one woody plant species naturalized outside of their native range and outside of cold-margin of their native range.Twenty-six woody plant species naturalized outside of their native range and outside of warm-margin of their native range. Among species that exceed the temperatures experienced in their native range, significantly more extend into colder than warmer conditions. While previous work has shown that small-ranged species are climate specialists, at risk of extinction, our results show large discrepancies between small-ranged species’ native climate conditions, and the climatic conditions in which they can survive and reproduce. Regression tree analysis showed that dispersal ability had predictive power, and that species with poor-dispersal ability (i.e. trees, shrubs) naturalized far outside their historic climate conditions. Thus, poorly-dispersed, small-ranged species that are able to tolerate conditions north of their historic distributions are particularly promising candidates for managed relocation. Whereas species that can tolerate conditions warmer than those in their native range might be at less risk of extinction than currently feared. Current modelling approaches may be insufficient for such species and more complex models should be developed.