Revising the sweet chestnut (Castanea sativa Mill.) refugia history of the last glacial period with extended pollen and macrofossil evidence

Recent advances in palaeoecology provide growing evidence of complex spatio-temporal patterns of tree species survival during the last glaciation. The distribution of Sweet chestnut (Castanea sativa Mill.) glacial refugia is still controversial. For this study we built an updated database containing almost all palaeobotanical data on Castanea published to date in the scientific literature and/or stored in the European and African pollen databases (EPD and APD). We used the collected data for assessing the sweet chestnut refugia during the Last Glacial Maximum (LGM). Furthermore, we identify the main changes in the distribution range of the species during the last 200 ka all over Europe. Confirmed chestnut refugia are the Transcausasia, where the species played a prominent role in the forest vegetation, and the Italian and Iberian Peninsulas, where it was restricted to scattered pockets providing favorable habitats. The species may have also survived in the Marmara region and in the Levant, while for the South-Eastern Balkans, north and central France and Northern Africa, the available evidence is too scarce yet for inferring local survival. Mountain ranges and seawater masses played a crucial role in determining the species survival during cold stages. Almost four fifths (79%) of the palaeobotanical sites with pre-cultivation Castanea records were found in the scientific literature, while the remaining 21% was extracted from the EPD and APD. Our study thus shows the growing importance of such curated databases as a key resource for palaeoecological synthesis products, emphasises the relevance of gaining a better spatio-temporal coverage by an extensive review of scientific literature, and underscores the urgent need of gaining new state-of-the art multiproxy records for assessing the causes and consequences of species survival under strongly varying climatic conditions. (C) 2019 Elsevier Ltd. All rights reserved.