Can species' traits predict recent range shifts?

Background/Question/Methods

Although there is mounting evidence that at least some organisms have moved to higher elevations and latitudes in response to recent climate change, there is little consensus regarding the extent to which different organisms will be able to rely on this response for future persistence.  In theory, species’ capacities to track climate change via range shifts will depend on their abilities to reach new areas via colonization and subsequently to establish viable populations in those new areas after arrival.  However, despite strong theoretical support for the effects of species’ traits on variation on colonization and establishment probabilities, it remains unclear whether innate organismal differences will yield predictable differences in the rate and extent of range shifts in response to climate change because external factors such as habitat fragmentation may instead constrain migration potential and have an overriding effect on the magnitude of observed range shifts.  We used a retrospective analysis of recent range shifts to ask whether life history or habitat traits predict why some species have already shifted distributions more than others in response to recent climate change.  We compiled traits and analyzed variation in observed range shifts for four published datasets to determine whether species’ traits can predict differences in the rate or magnitude of recent range shifts.  We hypothesized that traits related to colonization ability and establishment probability would be positively associated with greater rates or magnitudes of range shifts. Specifically, we predicted that range shifts would be positively related to traits related to greater dispersal distances (including dispersal modes and behavior), intrinsic rates of increase (measured by underlying components such as generation time and offspring number), and ecological generalization (assayed by metrics such as diet breadth, mating system, and climatic variance within the species’ range). We also hypothesized that traits related to colonization ability would be relatively more important for explaining current differences in range shifts than traits related to establishment probability.

Results/Conclusions

As predicted by life history and invasion theory, traits related to colonization ability (dispersal and intrinsic rate of increase) had positive effects on the rate or magnitude of range shifts. Traits related to establishment probability had more idiosyncratic effects, perhaps because ecological generalization should promote in situ acclimation and establishment in new areas.  Although signals were detectable, models had low to moderate explanatory power. Thus, although we found statistically and biologically meaningful relationships, they are unlikely to be of predictive utility.