Occurrence of favorable local habitat conditions in an atypical landscape: Evidence of Japanese pika microrefugia

Abstract

Species distribution models can be used to predict favorable areas for population persistence under contemporary climate change. However, these predictions are often based on broad-scale environmental variables and lack consideration of local-scale environments. Small areas where species are protected from unfavorable regional conditions by using locally favorable conditions, which are called microrefugia, are therefore often overlooked in current approaches used to conserve biodiversity. Here, using a two-step approach, we explored the existence of microrefugia of a cold-adapted mammal, the Japanese pika (Ochotona hyperborea yesoensis). We first identified broad-scale factors related to Japanese pika distribution and distinguished broadly favorable and unfavorable areas. Then, we assessed whether environmental conditions favorable to Japanese pikas existed at the local scale in habitats where they were present in unfavorable areas by focusing on thermal, vegetative, and ground conditions. We found that the Japanese pika distribution was substantially restricted by the mean summer temperature, suggesting that lower elevation areas were unfavorable for persistence. However, subsequent local-scale measurements indicated that while the average summer temperature in the Japanese pika habitats was higher in unfavorable areas than in favorable areas, rock interstices prevented the average and acute heat stress from reaching the thresholds known to limit Japanese pika activity. Moreover, summer thermal conditions in rock interstices in unfavorable areas were more stable than those in favorable areas. Taken together, our results indicate that lower-elevation areas are predicted to be unfavorable due to the broad-scale climate, but microclimates that allow Japanese pikas to behaviorally thermoregulate exist at the local scale, thereby suggesting the existence of microrefugia. In addition, winter thermal conditions did not differ among all thermal indices between the areas, and unfavorable areas possessed more developed vegetation and fewer rock interstices. Our results highlight the importance of examining local habitat conditions and suggest that using only broad-scale assessments may risk overlooking areas with a high potential for conservation. In the case of Japanese pikas, cool and stable microclimates at lower elevations were found to possess high conservation value in terms of enhancing population persistence under climate change.