380 DIFFICULTIES AND IMPORTANCE OF THE CONCEPT 



is interested only in sexual species because it is the recombining 

 of genetic factors through the sexual process which permits 

 formal genetics. The only event of genetic interest that happens 

 in asexually reproducing organisms is an occasional mutation 

 the effects of which will be invisible unless it is dominant or the 

 organism is haploid. Absence of sexuality in existing organisms 

 is almost certainly a secondary, derived phenomenon (Dough- 

 erty, 1955) and consequently does not require the setting up of 

 a primarily different species category. Finally, widespread though 

 it is in certain groups of organisms, asexuality is an exception 

 rather than the rule, and species can be defined and delimited 

 in most groups of organisms without any reference to loss of 

 sexuality. 



What can one do if one wants to apply the species concept 

 to asexual organisms in view of the breakdown of the usual 

 criteria? A number of different solutions have been proposed. 

 The first is to find a species definition which would be equally 

 suitable for sexual and asexual organisms. Du Rietz (1930) 

 thought that the following definition was satisfactory: "The 

 smallest natural populations permanently separated from each 

 other by a distinct discontinuity in the series of biotypes are 

 called species/' This forgets that asexual organisms do not form 

 "natural populations and that in asexual organisms every in- 

 dividual and every clone is such a distinct biotype. The clear 

 realization of this difficulty has led some authors to go one 

 step farther and abandon the biological concept altogether, be- 

 cause of its inapplicability to asexual situations. Frankly, it ap- 

 pears to me that there is nothing to recommend this solution. In 

 exchange for the biological species with all its advantages, it 

 reintroduces the morphological species with all its weaknesses 

 pointed out by most of the speakers at this symposium. 



A second solution is to restrict the term species to sexually 

 reproducing organisms and use it only in the sense ol biological 

 species. This proposal comes closer to a satisfactory solution, but 

 it still leaves open the question how to classify morphologically 

 differing individuals in asexual organisms. It has been suggested 

 to use for them a neutral term, such as the term binom, men- 



