PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY 377 



parallel the Wisconsin drift border in Ohio include the fence lizard 

 {Sceloporus undulatus), copperhead {Agkistrodon contortrix), and 

 upland chorus frog {P seiidacris brachy phono). To date there is no 

 sound paleontological support for the postulated ice margin popula- 

 tions of temperate biotas. 



On the contrary, evidence of Pleistocene spruce in southern 

 Louisiana and spruce and fir pollen in northern Florida and eastern 

 Texas seems impeccable (cf. Deevey, 1949; Braun, 1955). The 

 interpretation of the evidence, however, is not immediately shown. 

 Does it prove the existence of boreal forest at this latitude? Or does 

 it reflect an azonal mixture of temperate and boreal floras through- 

 out the unglaciated east as Braun (1955) and Drury (1956) main- 

 tained? Presently spruce grows near sea level in Connecticut and 

 southern Michigan, 400 to 500 miles beyond the southern limit of 

 spruce-fir-jack pine boreal forest. The Florida and Texas records of 

 boreal elements may also represent marginal populations of species 

 whose position of dominance lay farther north. We need not insist 

 that fossil spruce meant boreal forest in Texas and Louisiana, but it 

 may well represent population outliers of boreal forest occupying 

 Kentucky and the Carolinas. 



An area of intense frost action extending 50 to 100 miles south 

 of the ice sheet is generally accepted by geologists (Flint, 1957), 

 at least for eastern North America. Denny's studies (1951, 1956) of 

 periglacial land forms in unglaciated Pennsylvania are relatively 

 conservative, Peltier's (1949) more sweeping in their paleoclimatic 

 conclusions. Quite recently a series of herb-dominated pollen zones 

 have been reported from inorganic sediments in eastern North 

 America (Andersen, 1954; Davis, 1957; Deevey, 1951; Leopold, 

 1956; Livingstone and Livingstone, 1958; Martin 1958a). I consider 

 these findings as palynological confirmation of Full- and Late-glacial 

 tundra zones. 



At this point it may be helpful to insert a definition. Within the 

 scope of the term tundra I would include the following: (1) treeless 

 vegetation in the Arctic; (2) treeless Alpine zones on temperate and 

 tropical mountains; (3) pollen zones in Pleistocene sediments featur- 

 ing high percentages of herb pollen plus a small amount of spruce 

 and other boreal tree pollen. 



There is no question of floristic identity between these communi- 

 ties. As an example. Ambrosia, an element in the Late-glacial pollen 



