* \ 



, 4' 



.i^f 



■^ ^ 



i I 





'K 



■ m *.-.^ 



FIG. 27-5 Lions In the 

 ^ [^jt^ ij Ambosell Game Refuge, 

 '■'•^t'VS^ ' Kenya (courtesy S. Glldden 



"•s"' „ Baldwin). 



of the submontane rain-forest (subtropical zone) is 

 derived almost entirely from the rain-forest at lower 

 elevations. The montane rain-forest (temperate zone) 

 is of more recent origin than the sub-montane forest 

 and consequently derived part of its fauna from it. In 

 addition, the montane forest contains many species 

 of both animals and plants that have dispersed into 

 it from higher latitudes both to the north and south 

 where these species occur in temperate climates at 

 lower elevations. Some very high peaks extend above 

 the tree-line to produce alpine meadow (paramo 

 zone). The fauna and flora of this community are 

 derived almost entirely by lateral dispersal of or- 

 ganisms from extreme southern South America 

 (Chapman 1917). 



ANIM.^L ADJUSTMENTS 



Like the flora, the fauna in the tropical rain 

 forest is very rich in species (Table 27-1). Bates 



(1864) tells of finding 18 spfecies of swallow-tailed 

 butterflies within 10 minutes' walk of his house in 

 tropical South America. This is to be compared with 

 only about 20 species in all of North America north 

 of Mexico. Apparently, however, the density of in- 

 dividuals in tropical species is low. This is under- 

 standable, since the greater the number of species in 

 an area, the greater becomes the competition among 

 them for living space, and each is forced to withdraw 



TABLE 27 I Diversity of fauna at various latitudes (Dobihansky 

 1950). 



Tropical biomes 345 



