A test of climate change refugia in the mountains of California
Interest in the idea of climate change refugia has increased as natural resource managers seek targeted climate adaptation solutions. We used genetic and survey data to conduct a rare test of whether particular habitats are acting as refugia, buffering populations from recent climate change. We also examined whether hypothesized connectivity among meadows is supported. Montane meadows are a particular focus for this study because of their importance to animal communities, hydrological function, and human recreation and economy.
We used data from the Belding’s ground squirrel (Urocitellus beldingi), which has severely contracted its range in conjunction with the last century’s increasing temperatures and precipitation. We conducted both simple surveys of presence/absence as well as analyzed persistence over time compared to surveys conducted in the early 20thcentury. We predicted that refugial meadows would increase persistence of populations and thus show higher rates of occupancy and increased genetic diversity. Moreover, we used these population data to test whether hypothesized connectivity among meadows increases gene flow and diversity.
The amount of climate change was characterized by comparing recent downscaled PRISM data (1970-1999) to historical values (1910-1939). 267 U. beldingisampled at nine sites across California were analyzed at 12 microsatellite loci.
Across California, extirpation rates over time were lower for U. beldingi populations in sites where temperatures had changed the least. Focusing in on Yosemite National Park, occupancy rates were higher for meadows that were hypothesized to be refugia. Populations found in meadows where the magnitude of climate change was small had higher genetic diversity, indicating that they had persisted longer, as predicted. Higher connectivity values were also associated with increased allelic richness and with higher gene flow. The increasing frequency of extreme weather events was also considered.
These results show clear support of a refugial effect in montane meadows based on recent climate change. Thus this study introduces a multidisciplinary method for testing the concept of climate change refugia, as well as revealing one of the first instances that it is biologically relevant. The next step will be to understand the mechanisms that are creating refugia. Given limited management resources, there is a growing need to increase the effectiveness of climate adaptation actions. Climate change refugia will be important tools for conserving populations, genetic diversity and evolutionary potential.
This research was supported by the California Landscape Conservation Cooperative.