Specialists in ancient trees are more affected by climate than generalists

Ancient trees are considered one of the most important habitats for biodiversityin Europe and North America. They support exceptional numbers of specializedspecies, including a range of rare and endangered wood-living insects. In thisstudy, we use a dataset of 105 sites spanning a climatic gradient along the oakrange of Norway and Sweden to investigate the importance of temperature andprecipitation on beetle species richness in ancient, hollow oak trees. We expectedthat increased summer temperature would positively influence all wood-livingbeetle species whereas precipitation would be less important with a negligible ornegative impact. Surprisingly, only oak-specialist beetles with a northern distributionincreased in species richness with temperature. Few specialist beetles and nogeneralist beetles responded to the rise of 4°C in summer as covered by our climaticgradient. The negative effect of precipitation affected more specialist speciesthan did temperature, whereas the generalists remained unaffected. In summary,we suggest that increased summer temperature is likely to benefit a few specialistbeetles within this dead wood community, but a larger number of specialists arelikely to decline due to increased precipitation. In addition, generalist species willremain unaffected. To minimize adverse impacts of climate change on this importantcommunity, long-term management plans for ancient trees are important.Funding agencies: Norwegian Environment Agency