The importance of stability throughout time in affecting the geographical pattern of endemism richness

Climate change is one of the greatest threats to plant endemisms, particularly in mountain ecosystems that often show a high rate of endemism. Studies suggest that current centers of endemism are typically located in areas where the rugged mountainous topography buffered the effect of past climate changes and will probably buffer also the future changes. To evaluate climatic stability we assessed shift in distribution of Köppen climatic types form last interglacial to present. Using species distribution models, we projected the climatic niche of 100 plant species endemic or subendemic to SW Alps (about 60% of all endemic and subebdemic species) in past (i.e., last interglacial, last glacial maximum and middle Holocene) and future (i.e., year 2070 using both an optimistic and a pessimistic scenario) climates. We detected a higher current endemism richness (both potential and known) in areas climatically stable during the past than in not stable areas. We found a significant positive correlation between richness throughout past climates and both potential and known current endemism richness. Similarly, we found a significant positive correlation between future potential endemism richness and both past stability and current potential endemism richness. Nevertheless, endemic species in the SW Alps will experience high range loss (65.5% and 82.3% in the optimistic and pessimistic scenarios, respectively), not counterbalanced by range gain in adjacent areas because of low dispersal capabilities. Our results suggest that, despite the ability of microrefugia to remain relatively stable and support high diversity in the future, absolute levels of endemism in the SW Alps will likely decline considerably, due to the inability of endemic species to disperse at a rate consistent with future climate change.