Glacial relict

A glacial relict is a population of a species previously common during a glacial period that retreated into refugia during interglacial periods. They are typically cold-adapted species with a distribution restricted to regions and microhabitats that allow them to survive despite climatic changes.

Examples:
 * The biogeography of various aquatic species deemed glacial relicts that are found in Lake Sommen is likely related to a different geography during the early history of the lake. One theory claims that aquatic species were transferred from the Baltic Ice Lake through a natural lock system in connection with a temporary advance of the ice-front during the Younger Dryas. On land, the unusual occurrence of dwarf birch near Sund is also judged to be a leftover from a cold geological past.