lina island. This small tree is Cercocarpus traskiae (Rosaceae); 

 fortunately, it thrives in cultivation and even if it does become 

 extinct in the wild, it will persist in botanical gardens. Another 

 southern California endemic, one that occurs in the Mojave Desert, 

 is the diminutive annual poppy, Canbya Candida (Plate 2 A). More 

 widespread endemics are California Buckeye {Aesculus califor- 

 nica, Plate 2D) and Digger Pine {Pinus sabiniana, Plate 2C). 



The largest number of plant species endemic to the state is 

 found in southern CaUfornia, followed by the central coastal 

 area in second place. Relatively few endemics occur in the desert 

 areas, the northern Sierra-Cascades, and the Central Valley. 



The reasons for the narrow geographical ranges of California 

 endemics are unclear. Some endemics, such as the lone Wild 

 Buckwheat {Eriogonum cpncwm; Polygonaceae), occur only on 

 specialized soil types which have narrow distributions. Other 

 species, such as Coast Redwood, are limited by climatic factors 

 — in its case the cool fog zone of the coast. But in most cases, 

 the reason for the rarity is not clear. It is probable that a number 

 of California endemics are evolutionarily "old" species that were 

 more widespread in the geological past and are now on a natural 

 road to extinction (and are often speeded along this road by 

 man). We know, for example, that Cercocarpus traskiae of Santa 

 Catahna Island has a fossil history going back several million 

 years. It is likely that this species (like a number of island en- 

 demics) has been unable to adjust to the climate of modern 

 California and that this is the reason it is so rare and unsuccessful. 

 Likewise, Coast Redwood and Sierra Big Tree {Sequoiadendron 

 giganteum) have extensive fossil records indicating that in past 

 millenia both were once more widespread than they are now. 

 Brewer Spruce {Picea breweriana), Santa Lucia Fir (Abies brae- 

 teata), and Catalina Ironwood {Lyonothamnus floribundus) 

 also all have extensive fossil records indicating that these are 

 "old" species that were once much more widely distributed. 



At the other extreme, a number of rare plant species are un- 

 doubtedly newcomers in an evolutionary sense. For example, 

 many of the newly described, highly restricted species of Oarkia 

 from the southern Sierra Nevada foothills are recently evolved. 

 This is also true of several species of tarweeds (Madia, Hemizonia, 



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