Occurrence of cryptic woody plant refugia in northern Eurasia since the Last Glacial Maximum (25-17,000 yr cal B. P.) to the present

Coarse-scale models that predict climate change-induced habitat losses may have over-estimated extinction threats due to their inability to capture small-scale habitat heterogeneity, and are difficult to validate. Proposed validations use current data as calibration and past data as verification. The Quaternary fossil record is thus essential to understand the mechanisms that have allowed past species persistence, and to improve our forecasting ability regarding their future performance, although it has too been affected by coarse-scale issues. Evidence for woody taxa populations north of the classical pollen-based southern refugia during the last glacial maximum (LGM) has recently come from DNA and macrofossil studies. LGM refugia existed as habitat islands in a matrix of unsuitable landscapes, from which populations expanded in the Holocene. Such small populations – cryptic refugia – are indistinguishable in the pollen record and coarse scale bioclimatic envelope models don’t detect them. Persistence of many species in future climates may, as it has in the past, depend on the preservation of cryptic refugia, and defining their physical environment is of great importance. This study aims at defining the physical characteristics – topographical and geomorphological – of cryptic refugia for 3 Northern Eurasian tree taxa and integrate the resulting relevant physical parameters to local species envelope models to improve our understanding of the role of cryptic refugia on species persistence during past climate changes, and so to better forecast biotic response to future climate changes.