BIOME AND BIOME-TYPE IN WORLD DISTRIBUTION 



595 



ward as narrow parallel zones. The broad- 

 leaved evergreen forest of south Chile is 

 strictly dependent on high rainfall, and is 

 accordingly excluded from the temperate 

 but xeric temperature zones on the Andes. 

 The operation of historic factors at the 

 level of the secular geological cycles like- 



PARAMO OR 

 BOREAL ZONE/ 

 (TREELESS)- 



/ SEA LEVEL 



PINE- 

 BALSAM 



MANO DE 



I'mTco' 



.-TREE 

 ■ FERN 



COFFEE 

 ZONE 



LEVEL OF/ESCARPMENT 



(O. BROMELIACIA 



(o. f)lavimemdris 



\l 



h 



: ■• O. FRANKLINI 



•■ •■• V •. ) 



|0. engelhardti / 



O. SALVINI (o. rufescens 



•0. FLAVIVENTRIS 



Fig. 228. Altitudinal distribution of sala- 

 manders of the genus Oedipus on the volcanos 

 of the Guatemalan escarpment. Figures at left 

 equal thousands of feet. (After Schmidt.) 



wise contributes to the major differences 

 between montane zones of the northern and 

 the southern hemispheres. 



A still greater contrast between the 

 mainly higher latitude Rockies and the 

 mainly lower latitude Andes lies in the de- 

 velopment of the subtropical forest zone, in 

 which both vegetation and animal life are 

 derived from the adjacent tropical forest 

 below, instead of from the latitudinal zone 

 connected with it by isotherms (Chapman, 

 1917). The historic factor of dispersal 

 along a north-south mountain range may 

 be combined with the vertical derivation 

 of distinctive species in the upper zones, 

 especially in correlation with postglacial 



climatic changes. This distributional ar- 

 rangement (Figs. 227 and 228) may be 

 seen in the salamanders of the genus Oedi- 

 pus in Guatemala (Schmidt, 1936). 



Merriam (1899) was right in part as to 

 the dominance of the temperature factor in 

 North America; but this theorem cannot 

 be generahzed for the rest of the world. In 

 South America the precipitation factor dom- 

 inates distribution, and in Eurasia the 

 isolated east-west ranges were connected 

 only by historical changes in climate, and 

 historical isolation (in the sense of geolog- 

 ical history) dominates the distributional 

 pattern. Thus, the "Life Zone" diagram of 

 Wolcott (Fig. 226), excellent for North 

 America, does not apply well to tropical 

 South America or to Mount Kihmanjaro. 



MINOR TERRESTRIAL BIOMES OF 

 VARYING SIGNIFICANCE 



There remain a few conspicuously dis- 

 tinct biotic formations that do not fall 

 readily into a classification of biomes. The 

 waif biota of oceanic islands exhibits some 

 of the difficulties of community definition 

 of the ocean itself, for the transition, from 

 New Guinea to Easter Island, for example, 

 is gradual, and the ultimate dependence of 

 island land biotas on larger land masses for 

 their origin and upon the ocean itself for 

 their continuity and nourishment is obvious. 



The forest communities of eastern Aus- 

 tralia, Tasmania, and New Zealand differ 

 sharply from each other in biotic composi- 

 tion. They exhibit striking correlations in 

 floristic composition with the broad-leaved 

 forest of southern Chile as well as (in part) 

 with the coniferous araucarian forests of 

 Chile and southern Brazil. Their faunal re- 

 lations, however, are completely std gen- 

 eris. The distributional pattern in these 

 cases is dominated by the historical factoi 

 (p. 682). 



THE MARINE BIOME-TYPE 



Distinguishing as we do between the rel- 

 atively uniform and operationallv inte- 

 grated biomes, and the concept of biome 

 type, by means of which the biomes may 

 be grouped in a logical way, and by means 

 of which the concept of the biome may be 

 made to take into account the biotic con- 

 cepts of historical biogeography, we are 

 still faced with a major difficulty in the 



