Greasewood of the Great Basin (Sarcobatus vermiculatus, Cheno- 

 podiaceae) is an indicator of saline soils. In many areas of the 

 West, various species of brome grass (Bromus dpp., Gramineae) 

 are indicators of overgrazing, as is Basin Sagebrush (Artemisia 

 tridentata, Compositae). Knobcone Pine is an indicator of fire 

 within recent decades. Thus, the presence of certain species in an 

 area provides insights into the ecological status and history of 

 the area. The same is true of a fire-induced plant community; its 

 presence in areas that would otherwise support other plant com- 

 munities is an indication of fire in the history of the area. The 

 presence of Coast Redwood is an indicator of extensive coastal 

 fogs. The AlkaH Sink Scrub with its characteristic assemblage 

 of desert shrubs is, as its name implies, an indicator of alkaUne, 

 or at least, saline soils. The presence of certain indicator species 

 tells a great deal about the general ecological characteristics of 

 an area; the concept is particularly important to agriculturaUsts 

 who may be interested either in the future agricultural prospects 

 of an area or in whether a plot of land is being properly managed. 



Ecological Races 



Some years ago, A. R. Kruckeberg, then a graduate student 

 in the Department of Botany of the University of California, 

 Berkeley, devised a series of experiments aimed at testing the 

 presence of ecological races within certain plant species of Cali- 

 fornia that were known to occur both on serpentine (in some 

 areas) and off serpentine (in other areas). Kruckeberg filled 

 several planter boxes with serpentine soil and others with ordi- 

 nary garden soils. Among the plants Kruckeberg worked with 

 was an annual blue- or white-flowered giUa, Gilia capitata 

 (Polemoniaceae, Plate 3 A). This species has populations that 

 occur on serpentine and others that occur on other soil types; 

 plants from the two soil types are indistinguishable morpho- 

 logically. Kruckeberg collected seed from serpentine and from 

 non-serpentine populations and grew the offspring on both 

 serpentine and non-serpentine soils. In general, seedlings from 

 non-serpentine populations grew very well on non-serpentine 

 soils, but did very poorly on serpentine soils. The latter either 



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