206 Increase in Number of Species 



species, although interfertile experimentally, in nature appear to 

 be quite independent, non-mixing phylogenetic lines (Stebbins, 

 1950; Clausen, 1951). An equally plausible alternative explanation 

 is that the three are distinct species, that the entity hanseni is the 

 most primitive of the complex, and that the entities reflexa and 

 nevadensis evolved in opposite adaptive directions from a hanseni- 

 like ancestor. The intermediate nature of hanseni is explained just 

 as satisfactorily by the postulate that hanseni is a "living fossil" 

 or a near-prototype as by the postulate that it is of hybrid origin. 



In apomictic species and in species arising suddenly from spon- 

 taneous mutation, arbitrary taxonomic difficulties of another sort 

 are encountered. Especially in polyploid plants, completely isolated 

 polyploid phylogenetic lines may be so like the parents that without 

 living material for fertility tests and cytological preparations, rela- 

 tionships are obscured, and identification is hazardous (Wagner, 

 1955 ) . 



Mayr (1942), Stebbins (1950), Clausen, Keck, and Heisey (see 

 Clausen, 1951), and others have explained a multitude of other 

 species and their component parts which are difficult to interpret. 

 Because of the large number of puzzling examples there has been 

 much argument in the literature concerning the definition and 

 application of the terms species, subspecies, races, and similar 

 categories. The preceding examples ilkistrate fully the nomen- 

 clatorial problem in designing a uniform system or code for listing 

 and cataloging taxonomic entities as they are found in nature, 

 particularly for the sliding scale in values shown by "species in 

 the making." The only biological problem involved is to ascertain 

 the place of these entities in relation to evolutionary and/or 

 ecological processes. This can be done, not by deciding what name 

 to give them, but by comparing morphological and biological data 

 acquired by a study of specimens. 



Because the primary concern of a naming system is the record- 

 ing of data, it follows that the most satisfactory choice of names 

 or categories is the one which will serve as the best vehicle to 

 record desired data fully and clearly. This leaves much to the 

 judgment of the taxonomist when confronted by situations represent- 

 ing different levels of complexity and evolutionary development. 

 Nothing would seem to be gained by attempting to restrain or con- 

 trol the use of categorical names in systematics beyond the rather 

 broad concept expressed above (Osborn, 1902). 



