RELATIONS AMONG SPECIES 



389 



CRITICISMS 



The biome scheme has a sound basis and does pro- 

 vide a great deal of flexibility. However, its value as 

 a means of classifying ecological communities suffers 

 from the problems of such classification. This is true 

 even if one ignores the fundamental things preventing 

 complete accuracy in a distribution scheme. The 

 state of ecological knovv-ledge is such that few ecologi- 

 cal units definitely are agreed upon by ecologists, so 

 that no uniform basis for classifying vegetation exists. 

 Primary difficulties arise from disagreement as to 

 what constitutes a serai stage or a climax: some 

 ecologists classify nonclimatic climaxes as serai 

 stages; others classify them as climaxes. Also, the 

 exact limits of individual serai stages or climaxes are 

 not agreed upon. 



Biomes are similar to community types in that both 

 normally have organisms of a single adaptive type, or 

 growth formation. Although community types are di- 

 agnosed strictly in this manner, many biomes can 

 share a single growth formation and one biome can 

 encompass many growth formations. Such complex- 

 ity creates a problem in recognizing biomes and 

 studying their interrelationships. If biomes always 

 followed a definite distribution pattern in nature, the 

 difficulties would be reduced. However, regular pat- 

 terns are not common. Due to complex variation 

 among environments, biomes might assume a mosaic 

 of unrelated but adjacent formations. Therefore, 

 there can be a problem in placing a particular climax 

 in one or another biome. 



Another criticism of the biome and many other 

 schemes is that most to almost all organisms are ig- 

 nored. To a certain extent, this criticism of the bi- 

 ome is reduced if the dominants of each serai stage 

 and climax are discovered and named. However, 

 even if dominants are known, knowledge is insuffi- 

 cient for explaining many relationships among com- 

 munities. Such minimum information obscures the 

 concept of a community as a sort of superorganism. 

 Also,' lack of data hides the fact that a community 

 has a place or center of origin where it first became 

 an entity, and that, through time, a community has 

 established various relationships internally and with 

 other communities. 



Because the biome concept gives little idea of the 

 evolution of areas, it is somewhat static. The biome 

 scheme tends to hide the dynamic nature of areas 

 where everything indicates change. There are sea- 



sonal changes in composition and progressive changes 

 in the internal features and entire distribution of 

 areas. Moreover, these changes can be traced back 

 through geological history in a study of geoflora. 

 Therefore, the contrast is startling when dynamic 

 data are used to convey the idea of permanently fixed 

 distributions of organisms. 



BIOTIC PROVINCES 



The scheme of biotic provinces in its most modern 

 form was proposed for North America by L. R. Dice 

 in 1943. A biotic province is an ecological unit that, 

 except for islands, occupies a continuous geographic 

 area (Figure 19.27). Each province covers a large, 

 uninterrupted space having one or more ecological 

 "associations." Each province supposedly is some- 

 what equivalent ecologically and is characterized by 

 climate. However, a biotic province's greatest sig- 

 nificance is as a primary center of possible evolution, 

 each province somewhat conforming to the ranges of 

 fairly distinctive variants of individual species. For 



Figure 19.27 The Biotic Provinces of North America. Provinces are 

 incidoted but not named. (After vorious sources.) 



