Ice Age Genomic Tracking of Refugia and Postglacial Dispersal

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Understanding rates of migration and resilience to climate change is important for explaining both the distribution of single species and anticipate how ecosystems may respond to climate change. There are two vigorously debated questions about the response of NW European biota to past climate changes: 1) glacial survival vs tabula rasa and 2) Reid´s paradox of rapid plant migration through seed dispersal vs. survival in cryptic refugia just south or east of the ice sheet. These are related as survival in any northern refugia would suggest local dispersal rather than the rapid dispersal rates that are needed from southern refugia. While we have learned a lot about dispersal routes from phylogeography and about glacial refugia from macrofossils, pollen and, more recently, ancient DNA (aDNA), we have never been able to trace plant migration routes back in time. Our lab is at a step-change in answering these questions as we now have a full genome reference library for the entire flora of Norway and adjacent regions (>2000 species), which will allow us to develop genomic markers identifying not only species, but genetic variation within species, in ancient sediment samples. In addition, we have >20 sediment cores already analysed for vascular plant aDNA using metabarcoding, and a further 20 are in the pipeline. Based on these and 12 new cores, we will select samples that contain key species representing different bioclimatic zones (boreal trees, dwarf shrubs, arctic herbs), and re-analyse them for within-species genetic variation. This will be complemented by analyses of contemporary phylogeography of the same species. This will allow us to identify refugia areas and trace migration routes back in time by different components of the ecosystems. The results of this study will open a new era in studies of species abilities to respond to climate changes (palaeo-phytogeography) and enable us to model the effects of current global warming more accurately than before.