In biogeography, particularly phytogeography, 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 nunataks.
[1] Its antithesis is the tabula rasa hypothesis, which posits that all species have immigrated into completely denuded land after the retreat of glaciers.
[2] By the mid-20th Century, the nunatak hypothesis was widely accepted among biologists working on the floras of Greenland and Scandinavia.
[3] However, while modern geology has established the presence of ice-free areas during the last glacial maximum in both Greenland and Scandinavia, molecular techniques have revealed limited between-region genetic differentiation in many Arctic taxa, strongly suggesting a general capacity for long-distance dispersal among polar organisms.
Moreover, populations that survived on icefree land have probably in most cases been genetically flooded by postglacial immigrants.