biogeography Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time. Organisms and biological communities often vary in a regular fashion along geographic gradients of latitude, elevation, ...

, particularly

phytogeography Phytogeography (from Greek φυτόν, ''phytón'' = "plant" and γεωγραφία, ''geographía'' = "geography" meaning also distribution) or botanical geography is the branch of biogeography that is concerned with the geographic distribution o ...

, the nunatak hypothesis about the origin of a biota in formerly glaciated areas is the idea that some or many species have survived the inhospitable period on icefree land such as

nunatak A nunatak (from Inuit ''nunataq'') is the summit or ridge of a mountain that protrudes from an ice field or glacier that otherwise covers most of the mountain or ridge. They are also called glacial islands. Examples are natural pyramidal peaks. ...

s. Its antithesis is the '' tabula rasa hypothesis'', which posits that all species have immigrated into completely denuded land after the retreat of glaciers. By the mid-20th Century, the nunatak hypothesis was widely accepted among biologists working on the floras of

Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an island country in North America that is part of the Kingdom of Denmark. It is located between the Arctic and Atlantic oceans, east of the Canadian Arctic Archipelago. Greenland is t ...

and

Scandinavia Scandinavia; Sámi languages: /. ( ) is a subregion#Europe, subregion in Northern Europe, with strong historical, cultural, and linguistic ties between its constituent peoples. In English usage, ''Scandinavia'' most commonly refers to Denmark, ...

. However, while modern geology has established the presence of ice-free areas during the last glacial maximum in both

and

, molecular techniques have revealed limited between-region genetic differentiation in many

Arctic The Arctic ( or ) is a polar regions of Earth, polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Canada (Yukon, Northwest Territories, Nunavut), Danish Realm (Greenla ...

taxa In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

, strongly suggesting a general capacity for long-distance dispersal among polar organisms. This does not directly disprove glacial survival. But it makes it less necessary as an explanation. Moreover, populations that survived on icefree land have probably in most cases been genetically flooded by postglacial immigrants.

References

Biological hypotheses Phytogeography Biogeography Ice ages Prehistory of the Arctic {{Glaciology-stub