Abstract: Understanding the historical and physiological context of species’ vulnerabilities to climate change is a crucial step in predicting the impact of climate change on biodiversity. However, few studies have compared the magnitude and mechanisms of extant species’ responses to climate change in both the past and the future. The goal of this study is to compare the magnitude of plant species’ range and trait shifts under past and future climate change and to predict potential “winners” and “losers.” By combining temporally contrasting range and niche projections, we show that range shifts in the next 50 years will need to be more extreme than in the past 6000 years to track climate niches in a large plant radiation. A new subset of physiological niche traits, particularly temperature and radiation tolerance, will be strong filters of range occupancy under anthropogenic compared with Holocene climate change. In the absence of migration, temperature niche shifts tracking the magnitude of climate change will also be required for many species to maintain their present ranges. Where range shifts occur, our results suggest that communities will be restructured differently in different habitats, with widespread range contraction in the mountains and potential latitudinal range expansion in the lowlands. Our study adds to a growing body of evidence that despite the threats posed by climate change to many species, not all species will experience unmitigated loss, and that it may be possible to predict which species are most at risk based on physiological and geographical traits.
