376 P. S. MARTIN 



existing range gaps and relict populations date from the Glacial 

 period. From the viewpoint of the biologist the foremost events in 

 terrestrial ecology of North America during the Pleistocene appear 

 to include the following: (1) the climatic sequence proper with its 

 attendant displacement of biotic zones; (2) the arrival of prehistoric 

 man; (3) the extinction of late Pleistocene vertebrates. To an un- 

 unknown degree these events appear interrelated. The first part of 

 my analysis is devoted to problems of climatic and environmental 

 change, the second to extinction and the effect of man. 



LATE PLEISTOCENE ENVIRONMENT 



In view of the relatively poor pre-Wisconsin fossil and sedimen- 

 tary record, it is expedient to concentrate on the last (Wisconsin) 

 glacial sequence. Environmental change during the Wisconsin 

 glaciation can be considered subequal to that which accompanied the 

 earlier (Nebraskan, Kansan, lUinoian) glaciations. This assumption 

 is based on the coincidence of the four glacial drift borders in eastern 

 North America, the four equivalent periods of glacial temperature 

 drop as recorded in oxygen-isotope analyses of marine foraminifera 

 from the equatorial Atlantic (Emiliani, 1955), and the apparent 

 sequence of cool and warm mammalian faunas found in unglaciated 

 North America (Hibbard, 1958). 



Generally, biogeographers keep abreast of modern findings in 

 glacial geology and are not deterred by such views as that of Scharff 

 (1912, p. 156) that glacial drift was formed by marine deposition 

 and that the climate of the Pleistocene was never colder than at 

 present. Admittedly, there is lack of agreement concerning Pleisto- 

 cene environment and life in the region where glacial geology pro- 

 vides least information, namely in the temperate and tropical zones 

 south of the drift border. Braun (1951, p. 145) felt that "... the 

 deciduous forest zone, although narrowed, maintained itself on the 

 Appalachian Plateaus in southern Ohio and Kentucky while glaciers 

 extended southward in Ohio." Thomas (1951, p. 166) followed suit: 

 "The distribution and the ecology of many Ohio animals, I believe, 

 raises strong presumption that they survived the Wisconsin, or 

 perhaps the entire Pleistocene, close to the glacial border; some 

 species in refugia within the limits of glaciated territory." Plants in 

 question include buckeye (Aesculus octandra), sweet gum {Liqui- 

 dambar), Agave, and Magnolia. Animals with distributions that also 



