Distributional Patterns of Vertebrates in the 

 Southern United States in Relation to 

 Past and Present Environments 



W, Frank Blair 



Department of Zoology, The University of Texas, 

 A iistin 



1 he thesis of this discussion is that the present 

 distributions of vertebrates in the southern United States, on the 

 Gulf and Atlantic coastal plains in particular, can be explained only 

 on the hypothesis of drastic ecological changes in the deep south in 

 the Pleistocene. The germ of this concept was stated by Adams 

 (1902). More recently, Deevey (1949) expressed the hypothesis 

 clearly and reviewed some of the supporting evidence in his general 

 discussion of Pleistocene biogeography. The argument is essentially 

 that at peaks of glacial advance into the northern United States 

 climatic and ecological changes in the southern United States were 

 so great as to drive warmth-adapted species into separate refuges in 

 Florida and Mexico. Blair (1951) referred to additional evidence 

 from the vertebrates. 



Braun (1955 and other papers) has been particularly vigorous in 

 opposition to this hypothesis and has argued that the conditions 

 that produced the Pleistocene glaciations had little effect in the 

 southern United States. 



I now reopen the question, reviewing some of the evidence cited 

 by previous workers and introducing additional material. The evi- 

 dence is concerned primarily with past and present distributions of 

 tetrapod vertebrates, other than birds. One item in the past distribu- 

 tion of fishes is cited, but the present distribution of this group is 

 excluded from consideration. Similarly, no treatment of birds is 

 attempted, because of the author's relative unfamiliarity with this 

 group. 



The area to which the discussion will be largely limited is the Gulf 



433 



