The effects of dispersal ability and climate velocity on the extent of species range shifts since the Last Glacial Maximum

Background/Question/Methods

Species distribution models (SDMs) have been widely used to determine how species ranges change over time in relation to climate change. However, these models rarely incorporate dispersal mechanisms or varying rates of climate change through time and across space. These factors are likely important in determining the ability of a species to respond to changing climates. In this study we assessed how climate velocity and the dispersal ability of a species were correlated with the extent to which a species can shift its range in response to climate change. We built SDMs for 122 mammal species located in western North America during the present and hindcasted them to five different time periods over the past 17,000 years, validating models with the fossil record where possible. SDMs were constructed using six different model classes and a single ensemble model for each species, in all time periods. We then determined the extent to which individual life history traits (e.g., body mass and home range size, correlated with dispersal ability in mammals) and local climate velocities influenced the amount of range shift observed in individual species between model classes and through time.

Results/Conclusions

Hindcasted SDMs indicate that mammals showed a variety of responses to climate change over the last 17,000 years, including stable, expanding, and contracting ranges. There were two consistent observations across all model classes. First, climate velocity is significantly associated with the extent of range shifts observed in mammals across the Pleistocene/Holocene transition. During this period, mammals showed larger range shifts in areas that experienced higher climate velocities. Second, life history traits (such as home range size) are important in determining the extent of observed range shifts during the early Holocene: species with larger home ranges undergo larger range shifts compared to species with smaller home ranges.  These results suggest that the variables important in predicting the extent of range shift observed in mammals for a given time period are a function of climate stability. However, no single model explained more than 20 percent of the observed variation in range shifts, so we explore other factors that may also be associated with range shifts.  The results from this study will help generalize the expected responses of species to future climate change.