Towards an Understanding of Taxonomy and Nomenclature
Peter S. Green
The Arnold Arboretum
Jamaica Plain, Mass.
The contentious article by G. G. Nearing in the January bulletin "What Name Shall We Use?" cannot be allowed to pass without comment. Partly because of the pain and exasperation it must cause all conscientious taxonomists but mainly because of the misunderstandings and misconceptions which are set forth in such a way that many innocent members of the American Rhododendron Society stand in danger of becoming misinformed and misled.
Firstly, what is taxonomy? Put as briefly as possible it is that branch of biology, including botany, which deals with the naming and classification of living organisms. All objects must have a name if they are to be referred to intelligibly, and plants are no exception. From the first, scientific names have been in Latin for that was the international language of the educated man. However, as more plants came to be known, the names, which had been descriptive in form, contained more and more words. Then in the eighteenth century, the famous Swedish botanist, Linnaeus, effected a great simplification when he established the binomial system. By this system names consist of two words, the first being the generic name and the second the specific (e.g.
Rhododendron maximum
, where
Rhododendron
is the generic name applicable to all
Rhododendrons
and
maximum
is the specific epithet for all the plants of that particular species). Linnaeus set about the task of renaming every plant then known (and, incidentally, every animal too) and his system of nomenclature is still the one in use. The whole of the eighteenth century was a period of world wide scientific exploration and hosts of new plants from hitherto unknown continents were being brought back to botanists in all the major countries of Europe so that the next 150 years saw hundreds of thousands of plants described as new to science. It is not surprising therefore, with communications such as they were, and with ignorance of geographic areas such as then existed, that many plants came to be described as new, not once or twice, but many times, often in a different country each time, and of course with different names (or synonyms as they are called). Mr. Nearing claims that, "some species have had as many as 50 different names applied to them" (although there must be very few, if any, that can claim such a long synonomy) but the reasons for synonomy do not arise, as he states, from the pleasure taxonomists get in changing names. No one was more aware of the chaos that resulted than the botanists themselves and to overcome it the Swiss botanist, Alphonse De Candolle, prepared a set of rules to govern the giving of scientific names which could be adhered to internationally, and which could be used to decide which of many synonyms was to be accepted as the correct one for a particular species or other category. At the first International Botanical Congress in Paris held in 1867 De Candolle's "Lois de la nomenclature botanique" were adopted; but this Congress was not functionally international in character and it was not until 1905 in Vienna that nomenclatural matters were considered at all extensively. Not every country, however subscribed to the laws adopted in Vienna and although there were Congresses approximately every five years, except for the war years, there was no international uniformity, several variants of the rules being followed in different countries. In particular many American botanists, led by N. L. Britton, adhered to the "American Code," as it was called, which differed in many basic principles from the laws followed elsewhere. Not until the end of the Congress in 1930 at Cambridge, England was there any true international agreement and the various versions were eventually blended into one with the Amsterdam Congress of 1935. Since then they have been adhered to in all countries whatever their language or politics, which, for an international matter, is some achievement!
At subsequent International Congresses since this date (1950, 1955, 1959), although the rules have been amended in many ways, almost to the despair of the editors, it is important to stress that no fundamental principles have been altered or introduced. In fact those amendments that have been designed only to bring greater precision and clarity.
One of the main principles in the Code, as the laws are now called, is that of priority of publication. It is a principle that is recognized throughout science, and indeed beyond. The first person to publish and establish a fact can lay claim to it, and the first person to describe a particular species and give it a scientific name can claim priority for this name. A species may have been named and described a dozen different times in a dozen different countries but only one of them can have been first. No one can deny the importance of this principle, nor its value in establishing, on an international scale, which of many names is the correct one. Basic to its application, moreover, is its importance as one of the main ways of achieving stability in nomenclature, for sooner or later the earliest names will he established for all plants. That this has not happened yet is a reflection of the facts that, on the one hand there was no unanimity in the laws before 1935, and on the other, there is far more work to be done than there are taxonomists to do it.
What of the
nomina conservanda
mentioned by Mr. Nearing? Scientific names of plants, as has been pointed out, are in two parts, the generic and the specific, and although with the change in the latter only that species is affected, any alteration in the generic name immediately changes those for all the species in that genus. With the proposal of De Candolle's laws it soon became apparent that many well known and familiar generic names, by the strict application of the principle of priority, would be upset by earlier yet obscure names. Much painstaking work, particularly by the botanist Otto Kuntze, soon revealed the extent to which established generic names would be upset by priority and as a consequence the concept of
nomina conservanda
was introduced into the International rules. (Not, as suggested by Mr. Nearing, because of public protest.) But, and this is important,
nomina conservanda
were introduced at the generic level not at the specific.
So much for the International Code. What of the various other misunderstandings raised by Mr. Nearing. First the reference to continuous shuffling of species and genera. As stated earlier taxonomy as well as dealing with the naming of plants is also concerned with their classification. To classify is a natural, almost instinctive, way of thought in all men and when one adds to this the necessity of being able, as it were, to "find one's way about" in the vast array of the plant world, (it is estimated that there are some quarter of a million species of flowering plants alone, not to mention varieties etc., nor ferns, mosses, fungi, etc.), classification becomes of fundamental importance. Plants are arranged by taxonomists into a hierarchical system of categories, partly because man commonly organizes knowledge in this way and partly because it reflects the degrees of natural affinity between the groups, or to put it in another way, it reflects to a considerable degree the extent of advancement and divergence that has occurred in past evolution. Species are classified into genera, genera into families, families into orders, and so on. Much of taxonomy is concerned with discerning the true affinities and relationships of the plants and as techniques develop and knowledge increases, so one's understanding of the natural classification changes. Perhaps as a result of exploration a new species which forms a link between genera is discovered, or in cytogenetics a new technique reveals hereditary and breeding relationships, so that what were believed to be two separate genera are shown to be more correctly considered as one, or at another level single species are shown, in reality, to consist of two. Such new facts have to be incorporated into the taxonomic system, for the natural classification should reflect all that is known about plants. During the last few decades much new information has been added thanks to genetics, cytology, ecology, palynology, embryology, etc.; information which was undreamt of by the botanists of previous centuries and generations who described the vast majority of plants known today, and to say "there is no hope whatever of finding an arrangement substantially more comprehensible than what the majority of botanists in the past have already more or less agreed upon" is to ignore all the active modern branches of botany. The botanists of the past would be staggered by the information now available for incorporation into the system which is, in fact, becoming far more comprehensible than ever before, though of course one needs some knowledge of modern biology if one is to understand the basis of the system. Unfortunately however when two genera are combined only one generic name becomes acceptable instead of two and all the species in one have to take new names in the other. Such changes accompany progress and with time will become more and more infrequent. As an example of how apparent shuffling arises let us imagine that in the past somebody has proposed the recognition of two genera instead of one, based on some relatively minor character in appearance, but that the authorities of the day, often conservative by nature, considered the distinctions too trivial for generic rank, reunited them and were followed by most other workers. However, with new facts recently discovered it is now shown that the apparently trivial distinctions reveal basic biological delimitations, so that the separation of the genera is re-established and, in some instances, familiar names are upset. These name changes are unfortunate from the point of view of stability but are unavoidable if science is to progress.
What about the names of authorities which are quoted immediately after the Latin name. Mr. Nearing cites the example of
Rhododendron nudiflorum
and says "
R. nudiflorum
Torrey robs Linnaeus of his name
Azalea nudiflora
Linnaeus," but in actual fact there has been no robbery. Mr. Nearing has misstated the case, for the correct way of writing the name in the former genus is
Rhododendron nudiflorum
(L.) Torrey and in this way Torrey is indicated as having taken Linnaeus' species and combined it to become a species of
Rhododendron
. We are told that "there have been nine other legal robberies of this name, all equally senseless, and all serving the personal vanity of some taxonomist." But the names of the botanical authorities are not cited for purposes of vanity (or honor) but for definite technical reasons, Most important of all they make it possible to distinguish between homonyms, that is, between those cases where the same name has been given independently to different species by different authors, (e.g.
Rhododendron glaucum
(Aiton) Sweet (1830) is not the same species as
R. glaucum
Hooker filius (1851), which is more correctly known as
R. glaucophyllum
Rehder). Furthermore the citation of authorities gives some indication to taxonomists where and when the name may have been published and in which collection or collections the type specimen may be preserved. Bearing these points in mind it becomes obvious how important it is for taxonomists to continue to cite the original authority of a name, even when it is transferred to another genus, such as is done with Linnaeus' name cited in parenthesis in the example of
Rhododendron nudiflorum
(L.) Torrey quoted above (Linnaeus' name being abbreviated by convention to "L.").
What then can be done to promote stability? There have been many attempts in the past (starting at the International Botanical Congress at Amsterdam in 1935) to establish the possibility in the International Code of conserving widely known specific names (
nomina specifica conservanda
) should they become threatened. Each time however, the principle of priority has been considered by the majority to be of greater importance, and many Americans in particular, have stood out against the concept of conserving names. There are many botanists, however, myself included, who knowing that the rules have been made by man, feel that plant names, when they are widely used in literature and by non-taxonomists, are more important than laws. Because of various technical difficulties that lie in the way of conserving specific names, British botanists at the last International Congress at Montreal in 1959 made proposals to allow for the rejection of specific names (
nomina specifica rejicienda
) meaning in this way to reject names which by the application of the rule of priority would upset one that was already well established and widely used. In large part due, I believe, to the confusion in many botanists' minds with the concept of this idea and that of
nomina specifica conservanda
(and the technicalities involved in conservation) this proposal was lost. I do not think that this will be the end of it, however, and it was decided in Montreal that the size of the problem should be investigated and that a list should be drawn up of all the important species whose names should not be allowed to be threatened. In fact part of the resolution passed at the Montreal Congress reads. "All organizations and all persons are invited to send to the General Committee lists of plant names for which stabilization seems important, whether or not these names are now threatened, each name appearing on these lists being accompanied by a statement of the general importance of the species," Whether the American Rhododendron Society has already submitted a list of what they consider to be important rhododendron species I do not know, but this is the action which should be taken and it approaches the action Mr. Nearing suggests in the last paragraph of his article.
Finally, I hope this attempt to present some of the true facts of taxonomy will not have been written in vain and that by it at least some prejudices concerning taxonomy and taxonomists will have been removed.