414 The Community 



favors the increase in game birds and mammals. Regions that are 

 broken up into many units of different vegetation types are said to 

 have "good interspersion" because the total length of community edge 

 is great and hence a large amount of ecotone habitat is provided. 

 Since coveys of quail tend to establish themselves where several 

 types of vegetation meet, the number of coveys supported by farmland 

 can be increased through a change from a few big tracts of woods, 

 brush, pasture, and fields to a greater number of smaller interspersed 

 tracts without altering the total area of any one type of vegetation 

 (Fig. 11.5). 



COMMUNITY COMPOSITION 



Communities inhabiting distinctive and commonly occurring bio- 

 topes are the most easily recognized, and their composition and 

 interrelations have been more extensively studied than others. A 

 biocenose of this kind is made up of a characteristic, but flexible, 

 assemblage of species without necessarily containing any species that 

 is exclusive to it. Certain types of species invariably occur in a 

 biocenose of a certain kind, but the individual species may vary 

 widely from place to place. In a prairie community grass-like plants 

 are always present and serve as the fundamental plant producers, 

 but in different regions quite different species of grass fill this niche. 

 Among the animals of this community fleet browsing forms, jumping 

 types, and burrowers are commonly present but the species, genera, 

 or even families of these typical members of the biocenose may differ 

 greatly, depending upon the region in which they are located. The 

 ecological relationships are entirely separate from the taxonomic af- 

 finities of the species since the latter depend upon the evolutionary 

 history of the area. Species having a common evolutionary origin are 

 placed in "faunal regions" or "fforal regions," and these subdivisions 

 may or may not correspond with ecological subdivisions. 



Communities may be large or small. Some may cover thousands 

 of square kilometers, such as a spruce forest in Canada, a prairie 

 community in central North America, a pine-land community in 

 southeastern United States, or an oceanic community. Other biocen- 

 oses, such as those occupying relatively uniform swamp, desert, or 

 lake biotopes, may have dimensions in hundreds of kilometers. The 

 biocenoses of ponds, tide flats, rivers, balds, alluvial sands, chaparral, 

 mountain meadows, and rocky plateaux typically occupy a more re- 

 stricted area. Smaller communities inhabit canyons, "hammocks" in 

 the everglades, mountain springs, tidal inlets, and clearings in the 

 forest. The plants and animals living on an isolated boulder, or in a 



