594 



THE COMMUNITY 



southward in mountains mainly in associa- 

 tion with temperature zones, desert and 

 lowland forest are carried upward in asso- 

 ciation with soil type and precipitation. 



The conspicuous southward extension of 

 animal forms in the climatic zones of the 



guanaco, is on the whole much diflFerent 

 from that of the Rockies. In the northern 

 hemisphere, the great extent of tundra and 

 taiga, by mere mass eflFect, dominates the 

 corresponding associated montane environ- 

 ment. In South America, the area of the 



Fig 226. Correspondence of latitudinal and altitudinal life zones in North America. (Modified 



from Wolcott. ) 



TAJUMULCO 



ACATLNANGO 

 FUFGO/ 



Fig. 227. Horizontal distribution of the salamanders of the genus Oedipus on the volcanos 

 of the Guatemalan escarpment; the discontinuities in the ranges of the cold-hmited high- 

 altitude species are explained by the fluctuations in altitude of the life zones in glacial and 

 postglacial times. (After Schmidt.) 



Rockies is matched by certain northward 

 extensions of lowland forms in the Andes, 

 the guanaco of Patagonia, for example, ex- 

 tending to southernmost Peru. 



Biotic zonation in the Andes in general, 

 in spite of the northward range of the 



temperate zones is restricted, their climate 

 oceanic rather than continental, and the 

 climatic effects of trade winds and ocean 

 currents are more sharply defined. This 

 helps to explain the fact that the Andean 

 araucarian forest does not extend north- 



