PLANT MIGRATIONS ACROSS THE NORTH ATLANTIC OCEAN 181 



Iceland by long-distance dispersal, whereas there is evidence that this was the 

 case by the immigration of the American element. 



Table 3 gives the breakdown of the floras of Greenland (Bocher, Holmen 

 and Jakobsen, 1957), Labrador and Newfoundland (Rouleau, 1956) as 

 well as Gaspe Peninsula (Scoggan, 1950) in a similar manner. The eastern 

 Amphi-Atlantic elements in all these areas are consistently under-represented 

 in types adapted to long-distance dispersal; in several instances the differences 

 between observed and expected numbers are statistically significant. The 

 percentage of Amphi-Atlantic species in the floras decreases from north 

 towards south. The percentage of anemochorous and zoochorous species 

 increases towards the south while the percentage of species not adapted to 

 long-distance dispersal decreases. This trend also is significant. In part, this may 

 be the reason why the Amphi-Atlantic element, which is essentially an Arctic- 

 Sub-Arctic element, is under-represented in types adapted to long-distance 

 dispersal. But there is no evidence to suggest that the eastern Amphi-Atlantic 

 species reached their present stations by long-distance dispersal. 



There appears to exist a discrepancy between the zoogeographical and 

 phytogeographical observations regarding Davis Strait as a biogeographic 

 barrier. According to Lindroth (1957) the Greenland fauna consists of about 

 one half Holarctic species and about one quarter each of Nearctic and 

 Palearctic species. The Palearctic influence is particularly evident in the 

 soil-bound fauna which is not easily spread across the sea, while most of the 

 Nearctic fauna can be more easily dispersed. The fauna of BaflSn Island, 

 however, has an almost purely Nearctic character. Lindroth (1960) has also 

 performed an analysis of the botanical aspects of the problem. 



I have examined the data presented by Lindroth from a statistical point of 

 view and found their significance doubtful. However, Lindroth treated the 

 flora of Greenland as a whole. Smith Sound between Greenland and Ellesmere 

 Island is hardly an important barrier for Arctic plants. If Davis Strait has been 

 a barrier this should be most clearly evident among more Low Arctic plants. 

 It should also be remembered that during the Post-glacial climatic optimum 

 (the Hypsithermal) many plants could grow in the Smith Sound area, but 

 they are now found only farther south. For this reason, I have made an 

 analysis of the Low Arctic element, here defined as species with a northern 

 limit in Greenland at or south of the Nugssuak Peninsula and on Baffin 

 Island at or south of the Pangnirtung Peninsula. The result of this analysis is 

 presented in Table 4. 



From the table it will be seen that no enrichment of types adapted to 

 long-distance dispersal is evident among the eastern Amphi-Atlantic taxa 

 penetrating into America. However, among the western plants penetrating 

 into Greenland and Iceland there is an over-representation of types adapted to 

 long-distance dispersal. Using the entire flora of Greenland as a basis for 

 comparison the difference becomes clearly significant. Taking the entire flora 



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