University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Faculty Publications from the Harold W. Manter Laboratory of Parasitology Parasitology, Harold W. Manter Laboratory of 1989 Tribune: Genus and Family: Concepts and Natural Groupings Armand R. Maggenti University of California - Davis Follow this and additional works at: https://digitalcommons.unl.edu/parasitologyfacpubs Part of the Parasitology Commons Maggenti, Armand R., "Tribune: Genus and Family: Concepts and Natural Groupings" (1989). Faculty Publications from the Harold W. Manter Laboratory of Parasitology. 105. https://digitalcommons.unl.edu/parasitologyfacpubs/105 This Article is brought to you for free and open access by the Parasitology, Harold W. Manter Laboratory of at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Faculty Publications from the Harold W. Manter Laboratory of Parasitology by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Tribune GENUS AND FAMILY : CONCEPTS AND NATURAL GROUPINGS Armand R. MAGGENTI University of California Davis, Department of Nenzatology, Davis, CA 95616, USA. A little over two hundred and fiftyyears ago Linnaeus to take the step beyond seeing whatothers had seen to (= Linne) began to maneuver his concepts of animal the realm of thinking what others had not thought. As arrangement into Aristotle’s logic of classes. Twenty- a result Darwin’s thesis on the origin of species has three years elapsed between the publication of his first influenced biology for over onehundred years and and tenth editions of (( Systema naturae D. The tenth Wallace is remembered for presenting a similar hypoth- edition (1758) is theacknowledged starting point of esis that his theology would not allow him to expand. zoological nomenclature.Often forgotten but highly Linnaeus provided the grist upon which Darwin and significant is the fact that he spent those intervening others worked. However, Darwin and others were lead- twenty years orchestrating the then known animals into ers in initiating the shiftfrom theconcept of a uti- the world of philosophy. litarian classification based on the procedures of logic Linnaeus’genius was conceivingthat science and that primarily functioned as an instrument for identifi- philosophy can blend and that theology, though highly cation,to themuch broader interpretation that the influential to his concepts, was not the al1 controlling diversity of organisms resulted from evolutionarydiver- unit. He was influenced by Aristotle’s logic of classes, gence (Mayr, 1969). Thus, there was a major shift from Plato’s “ essence ” and Thomistictheology. This may be identification to classification and the process of reason- best explained bysimplistic definiti0ns:science at- ing became inductive rather than deductive. Recently, temptsto delimitwhat is true;philosophy seeks to in nematology, there has been an inclination to revert to define truth; theology, which Linnaeus was unable to deductive reasoning in the formulationof classifications completely escape, intervenes in as much as the de- (Andrassy, 1976; Fotedar & Handoo,1978; Siddiqi, mands of faith supersede delimitation and definition. 1986). In these classifications the categories above the Understand, Linnaeus was polarized by the sixteenth species are basedon ana prioriarrangement of morpho- century observation : philosophia ancilla theologiae(phi- logic characters ratherthan on natural groupings as losophy is the maid-servant of theology). interpreted through known biology. To a large extent, and unfortunately so, science has Linnaen classification has not been without oppo- come to limit the genius of Linnaeus to G creating )) the sition and criticism. Attacks on the system generally arise binomial system of nomenclature. Binomial nomencla- from an inability to comprehend a rigid hierarchy with ture was extant hundreds of years before Linnaeus; his an inherent need forarbitrary ranking. The assignment proposa1 established the binomialas unambiguous. The of intractable values to ranks withinthe hierarchy would names and groups he offered are not important. The paralyze the system into a desinence that would preclude introduction of an unambiguous binomial nomencla- improvement. Perception of the intrinsic subjectivity of ture and thelogic ofclasses and its application tobiology the system allows for the incompleteness ofOur know- are important because for the first time thediversity of ledge of relationships and presents us with the oppor- living organisms was organized in a manner that rev- tunityto testalternate models of relationship, thus olutionized human thought. However, Linnaeus’ philo- maximizinginformation. Systematists should accept sophy remained Aristotelian and washe dedicated to the and welcome the fact that the systemwill forever remain application of Aristotle’s system of logic to classification provisional. (Tuxen, 1973). Later generations up to and including There are seven basic categories that prevail in the Darwinsucceeded in excising Linnaean philosophy modern interpretationsof Linnaeus’ hierarchies. Al1 are from Linnaeus’ proposa1 while retaining the essence of not those proposed by Linnaeus (classis, ordo, genus, a rigid hierarchy of categories andan unambiguous species, and varietas) butthose that newknowledge binomial nomenclature. demanded. After more than two hundredyears only fïve Darwin’s contributionsencouraged us to use Our (genus, family, order, class and phylum) permit US tO abilities to see what everyone else has seen andyet think place a species with any degreeof accuracy. Even these beyond this neurologic limitation.It is this that spotligh- didnot satisfy Our needto more accurately portray ted Darwin. Wallace, hindered by theology, was unable relationships;therefore, over the years moreprecise A. R. Maggenti ~~ ~ designations were imperative and the prefxes super- false faith or faith in a rigid system based on numbers and sub- were attached to the basic categories. cannot escape thereality thar taxaare based on zoologi- With no sense of the purpose of Linnaean hierarchy cal realities. Categories,no matter how depictedare some other terms have been introduced and have, not concepts; however, they are concepts based on natural unexpectedly, become the subjectof confusion because occumng units. they do not conveyrelationship nor do they add to The most objective of al1 categories remainsthe perception of nematode biology. The terms referred to species, for a further discussion of the objectivity and are : biotype, race and pathotype. On the other hand definition of the speciessee Maggenti (1983). The someterms that have received anotable degree of species category differs from al1 other divisions in the acceptance are : tribe, between family and genus, and hierarchy in that itsignifies singularity, distinctnessand group between genus and subgenus.However, asuseful difference (Mayr, 1969). Categories above the species as they are, they have not warranted recognitionby the are collective conceptsinasmuch as they have the International Commission of Zoological Nomenclature function of grouping and ordering by de-emphasizing forinclusion in the rules for “ binomial(trinomial) differences between species and emphasizing affinities nomenclature ”. It is not surprising that these perceptive among groups of species. Mayr (1969) States : “ Even additionsamplify the ability to expressrelationships though an operational definition for the higher catego- within the two most informative categories in the hier- ries does not exist, nor for therank which they signify, archy of classification; i.e., the genus and family. Both they do have anobjective basis because a taxon placed additions are designed to expandOur ability to cope with in a higher category (if correctly delimited) is natural, newknowledge of relationships without the need to consisting of descendants from a common ancestor. ” overinflate the basic categories. This simply means that Since there is no operational definition of the genus 1 genera do not have to be raised to families or families will adopt Mayr’s pragmatic definition: “ A genus is a to orders. Thus funher illustrating the genius of the taxonomiccategory containing a single species, ora Linnaean-Darwin-Mayr philosphy of classification and monophyletic groupof species, which is separated from perhaps,with an affordabledegree of magnanimity, other taxaof the same rank (other genera) by a decided Aristotle’slegacy to biology: the gft of the logic of gap. ” In general, the size of thegap is inversely classes. proportional to thesize of the taxon. Thisis a schooled This disquisition set-out to address the logical conse- observation and not a rule. quence of purporting to understand and accept that a In view of the fact that there is no operational defi- classification and ranking in a hierarchy reflect rela- nition of the genus and inasmuch as there is no dis- tionships. From the foregoing statements it should now tinctive single or group of characters thata priori make be evident that the backboneof a Sound classificationis a genus, then its circumscription must be sought else- entrenchedin Our perception of thegenus and its where. Since strict morphology cannot delineate thege- projected concept - the family. nus then the alternative to understanding the affiities Linnaeus in 1737 gave lasting advice in his dictum : among species must lie in their biology and ancestry. “ Its the genus that gives the characters and not the