494 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 63 



Three principal classes of sj)ecies are to be found in the arctic- 

 alpine environment : 



1. Widespread circumboreal species, meaning species with a world- 

 wide distribution in North Temperate regions, having a large ecolog- 

 ical tolerance (amplitude) that permits them to transgress two or 

 more major climatic, hence environmental, zones and plant formations. 

 In other words, this class includes species that might occur widely, 

 for example, in both coniferous forests and tundra. Such species 

 may thrive in arctic-alpine habitats simply by virtue of a wide phys- 

 iological tolerance rather than any particular genetic adaptation. 

 Certain species of the heather family, as bog rosemary {Andromeda 

 polifolia L. ; pi. 12) , provide good examples. 



2. Widespread circumboreal species represented in the Arctic- 

 Alpine by specially adapted, hardy biotypes that have become estab- 

 lished as separate physiological races, which may or may not be 

 morphologically marked. These are sometimes called ecotypes — 

 ecological races. An example here is the widespread species Ledum 

 fdlustre L. (Labrador tea; pi. 12), which has differentiated a race, 

 ssp. decwnbens (Ait.) Hult., that is found only in the Arctic. 



3. Endemic species found only in some part of the Arctic- Alpine 

 either with or without more than one race. These species may be ex- 

 tremely localized or virtually circumpolar; confined to the Arctic or 

 some part of the Alpine or common to both. There are of course minor 

 overlaps into the next vegetation zones at the lower limits of the 

 Arctic and Alpine. Several of the saxifrages, like Saxifraga ftagel- 

 laris Willd. and S. oppositifolia L. (pi. 5), and Diapensia lapponica 

 L. are good examples of widespread arctic-alpine species, endemic in 

 the sense used here. 



These must of course be arbitrary categories, and their sole function 

 is to point up the major patterns of distribution. It is very difficult 

 to categorize many species found growing in the Arctic-Alpine, for 

 the simple reason that we lack rudimentary data about their ecological 

 requirements and ofttimes have a poor picture of their distribution. 

 The classic transplant studies of Turesson, the team of Clausen, Keck 

 and Hiesey, Bocher, and others have provided ample evidence to con- 

 vince us that widespread species do differentiate ecological races in 

 alpine and arctic regions. They grew plants, transplanted from an 

 arctic or alpine habitat, under uniform conditions at lower latitudes 

 and elevations to determine whether their characteristic growth- form 

 was due to environment or heredity. The Clausen team added the 

 refinement of taking pieces from the same clone (same genetic in- 

 dividual) of certain plants, as grasses, and planting them at different 

 altitudes to see what the same genetic stuff could produce under dif- 

 ferent environments. All of these studies leave no doubt that in the 

 cases studied, at least, both environment and heredity have a strong 



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