Global climate change has already caused local declines and extinctions across continents and trophic levels. These losses are thought to occur because climate change is progressing too rapidly for populations to keep pace. Nonetheless, rapid climate-driven responses are possible, although we currently have little ability to differentiate between those species that can and cannot respond to climatic changes. Recent empirical work, however, has demonstrated that seasonally asynchronous climate change regimes — when a region is warming during some parts of the year, but cooling in others — are constraining species’ responses to climate change more strongly than rapid warming. Asynchronous regimes may therefore provide one metric that can help explain inter- and intra-specific differences in climate vulnerability. It is unclear, though, how common asynchronous regimes actually are nor what their broad-scale effects on biodiversity patterns may be. To address this gap, we couple an analysis of long-term North American climate trends with novel meta-population simulations to elucidate how the contemporary distribution of asynchronous regimes may be affecting dispersal and gene flow among populations.
Results/Conclusions
We found that seasonally asynchronous regimes are occurring throughout the majority of North America and that their current spatial distribution may be a strong barrier to dispersal and gene flow across many species’ ranges. Asynchronous regimes may be especially problematic for species whose ranges encompass the Inter-Mountain West, where there is strong spatial heterogeneity in the occurrence of asynchronous regimes. Thus, despite the fact that adaptation to climate change may potentially be more common and rapid than previously thought, species whose ranges overlap with asynchronous regimes will likely succumb to local declines that may be difficult to mitigate via dispersal.