Taxonrl 



PRINCIPLES OF NEMATODE TAXONOMY 



M. W. Allen 



University of California 



This discussion of the subject of taxonomy of nematodes is undertaken 

 vd.th some hesitation primarily because of the difficulty of getting 

 specialists to agree on the taxonon^ of even a small genus. The main 

 difficulty encountered is the fact that most nematode groups are not 

 well enough known to supply the basic information necessary to estab- 

 lish satisfactory classifications. One should keep in mind that in 

 most instances we are dealing with opinions and not precise data col- 

 lected from carefully controlled experiments. It is unfortunate that 

 the taxonomist cannot always undertake controlled experiments with the 

 populations with which he is concerned. He must deal in general with 

 dead specimens and these usually represent an extremely small sample of 

 any particular population. If we consider that each individual taxono- 

 mist has the right to express his opinion concerning facts ascertained 

 from the study of a few specimens that he assumes to be representative 

 of a population, it is surprising that there does exist a relatively 

 high degree of agreement concerning most nematode groups. 



One should, of course, begin a discussion of taxonomy by pointing out 

 the importance of taxonomy to all fields of biology. It must be obvious 

 that it would be impossible to communicate knowledge about organisms 

 without a system of naming. More important, it is necessary to have 

 permanent names for organisms, and these names must be supplemented by 

 information that will enable all workers to recognize a named species 

 each time it is encountered. This concept is as important in the field 

 of applied nematology as it is in ecology, evolution, morphology, or 

 physiology of nematodes. In all of these fields we must have accurate 

 identifications and a stable system of nomenclature if we are to make 

 lasting contributions to our knowledge of the biology and control of 

 nematodes. 



In order to illustrate some of the difficulties that are inherent in 

 taxonomic studies I will use, so far as is possible, some of my own work 

 as examples. In this way I can be as critical as is necessary and also 

 avoid offending any of my fellow taxonomists. Most discussions of tax- 

 onoity are usually concerned vrLth the species, and this is rightfully 

 recognized as the most important category in classification by most 

 taxonomists. Above the species level we have a varying nianber of col- 

 lective categories, the subgenus, genus, subfamily, family, etc. Also 

 there are, in most groups of animals and particularly those that are 

 well known, infraspecific rntegories. The best known and most widely 

 used of the officially recognized infraspecific groups is the subspecies. 

 There are a relatively few described subspecies in the nematodes in com- 

 parison to other animal groups such as insects, mammals, and bii^s . VJe 

 frequently forget the proper relationships that are intended to be 



