JARS v36n3 - The Case for Constancy in Plant Names
The Case for Constancy in Plant Names
1982 B. Y. Morrison Memorial Lecture (Speaker Introduction)
Dr. August Kehr, Hendersonville, N.C.
As human beings we resist change. We yearn for things that are permanent and enduring. Consequently, as plant people, we long to have plant names that will last, at least for our generation. Constancy in plant names is fundamental to a clear and concise communication system among plant people.
Unfortunately living things are not constant. They are always changing. Life is never static. As a result we must always face the necessity of modifying plant names consistent with new findings in plant science. It is essential, therefore, that we begin this presentation of our case for constancy in plant names by defining the kinds of change that offend our sense of botanical stability. Let me illustrate by giving you an example.
An Example of a Proposed Name Change
Rhododendron japonicum is a handsome species that is found commonly over a great part of the main island of Japan. It is one of the ancestors of the popular Exbury-type azaleas found in many of our gardens. The Exbury azaleas are items of great economic value to our nurserymen.
Rhododendron japonicum has been named variously as follows: (Wilson and Rehder 1921):
1846 Rhododendron molle Siebold and Zuccarini
1858 Azalea japonica A Gray
1864 Rhododendron molle var. glabrior Miguel
1867 Azalea mollis var. glabrior Regal
1869 Azalea sinensis var. glabrior Maximewicz
1870 Rhododendron sinensis Maximowicz
1871 Azalea mollis André
1908 Rhododendron japonicum Suringar
Thus R. japonicum was first named in 1846, but went through seven proposed or actual name changes in 58 years, until it reached its present name in 1908. For the last 74 years it has been spared the debasement of a name change, 74 years of respectability and validity. Now wouldn't it be logical to expect that a name that has been used without question for 74 years would have reached a point that an additional change would be unneeded, especially in the light of the fact that there is nothing about the living plant that even suggests a change? Not so, not so. It appears that someone in reading some obscure, forgotten, or otherwise overlooked literature has found a prior existing name that was given to R. japonica and has made a proposal to rename the plant. And what do you suppose that new name is? Listen carefully for you will find it hard to believe your ears. It is Rhododendron metternichii !
If such a proposed name change is approved, you may next ask what would then become of the complex of plants we presently know as Rhododendron metternichii , including variety kyomaruense , variety micranthum , variety metternichii and variety yakushimanum ? To respond, their names too would become invalid under the Code of Nomenclature and they would likewise have their names changed. Who can tell how many other plant names would have to be changed and re-changed before a semblance of tranquility would reign once more. This, then, is an example of our case for constancy in plant names. If the name R. japonica was good for 74 years and there is nothing new found in the living plant, or even herbarium specimens, there does not seem to be a legitimate case for changing the species name, even though the present Code permits it. Our thesis therefore is simply this: It is not the name of the plant which needs changing. It is the Code itself.
An Example of an Invalid Name
Let me present another example, this one an example of an invalid name. When Linnaeus published his monumental book, Species Plantarum , in 1753 he named 5 plants as Azaleas and 5 plants as Rhododendrons (Krüssman 1970). Thus back in 1753 the names Azalea and Rhododendron were co-equal and both were bona fide genus names. One of the 5 azaleas was Azalea procumbens , which was designated as the type plant for all species of the Genus Azalea. However, Azalea procumbens was later renamed Loiseleuria procumbens . Then in 1905 the genus name, Loiseleuria was placed on the conserved list of genus names. As a result, under the Code of Nomenclature, the name Azalea is no longer a valid name for use with any plant in the Genus Rhododendron . The name Azalea is consequently an improper one, again not because the plants have changed but because the rules of nomenclature permit it. I am absolutely certain that these rules, try as they might, will never submerge the name Azalea, invalid though it may be.
Having described the bad kinds of name changes to which we object, let us turn to the good things that are found in Latin binomials of plants.
Advantages of Binomial Names
To provide species names for at least 300,000 plants precisely, consistently, if not permanently, is recognized as an almost impossible task. When viewed in this light, the followers of Linnaeus have accomplished a monumental task of almost unbelievable magnitude and complexity. These plant classifiers have developed a system whereby, with two brief names written in Latin a plant may be recognized by anyone in the world. Prior to Linnaeus plant names were little better than Latinized common names or descriptions. For example, according to Wilson and Rehder (1927) Rhododendron luteum , discovered in about 1701, was named in 1703 by Tournefort as "Chamaerhododendros Pontica, maxima, Mespili folio, flore luteo".
We all know that common names lack precision. They do not identify plants universally. Likewise the same common name may be used for several plants. Therefore their practical use is limited. It is likely that common names are more useful for animals. For example, an elephant is most likely known as an elephant the world around. However, the plant elephant ears might not be known by more than half of us here tonight.
Although there are those of us who have become irritated over the frequent name changes such as the ones cited earlier, we are the first to concur that Latin or botanical binomials are exact and precise. A single name describes or identifies without question one single kind of plant and clearly distinguishes it from all other plants in the world. An illustrated botany book may be written in Japanese, but those of us who read only English can readily understand the illustrations whenever the Latin name is given.
Botanical names with their genus and species also classify the plant as well as name it. Thus when a plant is named Rhododendron japonicum it is known to be related to about 1000 other species in the Genus Rhododendron . Our case therefore is only one of objecting to the all-too-frequent changes in species names, not the system of naming.
We will now consider a universal problem faced by plant classifiers, the problem of natural variations.
The Problem of Natural Variation
The determination of plant names can never be an exact science because no one has ever come up with an exact definition for a species. What constitutes a species is judged and decided largely by the individual classifier. I shall never fully recover from the mortification I suffered in my final oral doctoral examination when I was asked to define a species and could not do so. It was only later that I learned that there is really no one definition.
Species are impossible to define precisely because no two individual plants in a species are exactly alike. Thus all that can be done is to attempt to place reasonably similar individual plants into groups that are most nearly alike. Problems arise as we get farther from the central core of the plant population and approach individual plants that become borderline. And there will always be borderline plants because of natural variations. These natural variations are a function of all living plants and animals, and reflect the fact that in the history of the world it was the sum total accumulation of these small variations that caused species to arise in the first place, and indeed is still causing them to arise.
I realize that these comments bring us close to a discussion of evolution and the origin of species, a topic far beyond the scope of this lecture. However, systematic botanists and zoologists involved in classification must be familiar with exploring and charting patterns of variation, and inevitably these patterns of variation must lead to an understanding of the evolution of species. May I somewhat parenthetically, then, state my own conviction in this regard.
As a scientist I am compelled to accept the Theory of Evolution as first proposed by Darwin. The evidence in fossils of the appearance and disappearance of species over the millennia cannot be disregarded. In like manner I am compelled to accept the Bible as the inerrant and inspired Word of God. If one accepts and interprets the Bible diligently, he sooner or later realizes there is absolutely no conflict between the teachings of the Bible and the Theory of Evolution. In my view the two complement and supplement each other in a manner that approaches the miraculous.
With that clarification, let me briefly cite an actual experiment in plant variation and the evolution of species published several years ago (Smith, Stevenson, Kehr 1958). I am familiar with it because I was one of the authors.
Example of Evolution of New Species
In the Genus Nicotiana the basic somatic chromosome number of a species is 24. If we hybridize two selected species, we arrive at a hybrid with 24 chromosomes, 12 chromosomes from each parent. Almost all such hybrids between two Nicotiana species are sterile, but if we treat the hybrid seeds with the drug colchicine we can double the chromosome numbers and obtain a true breeding and fertile group of plants with 48 chromosomes. By several successive steps of hybridization and subsequent doubling of chromosomes, a population of relatively true breeding and fertile plants with an almost unbelievably high number of 144 chromosomes was developed. By selfing individual plants of this high chromosome population for 10 generations, three distinct races of plants with 108 chromosomes were developed; in brief, each race had lost 36 chromosomes in 10 generations.
The three races that had resulted were distinct morphologically from each other and each of their ancestral species. Likewise they would not interbreed effectively between themselves nor with their ancestral parental species. Consequently they were isolated and as such were essentially distinct new species, which if found growing in nature, would be accepted by most classifiers as three entirely new species. The origin of these three races therefore represented the development by actual controlled experimentation of new plant species in much the same manner as new species arose in the past, and, we might say, are still arising.
As long as living organisms continue to produce variations in their offspring, there cannot be an exact system of classification. Hence we will never arrive at a point where changes in names of plants will never cease to be made because species themselves are not immutable, and certainly are not pure lines. Having made the two points that a number of name changes will of necessity always be with us, and that species arose in the past and are continuing to arise by natural variation, you may wonder wherein lies the case for constancy in plant names. I shall explain and have a little enjoyment in doing so.
Classifying the Classifiers
We have all heard of plant classifiers as being either lumpers or splitters, lumpers if they combine two or more species into one species, and splitters if they divide one species into two or more new species. I should like to provide you with an entirely different classification of the classifiers, knowing that in so doing I am placing my reputation, such as it may be, in jeopardy. Of course, perhaps no living plant classifier falls exactly into the group I am proposing. This classification is three-parted.
First are those classifiers that are knowledgeable about plants because they have studied living plants in all their aspects. They have made frequent field trips to study the plants in their native habitats and observed the natural variations as they exist in nature. They are familiar with the breeding behavior of these plants and are familiar with the myriads of hybrids that exist. They know the chromosomal behavior and chromosomal variations of their plants. Likewise they know the physiological variations, even pathological behavior. In brief, they are well qualified to make the many decisions for plant classification because they have considered all available evidence. Let us call this first classification the "Good Guys". May their numbers ever increase.
In the second classification are the classifiers who limit themselves largely to the four walls of their herbarium, studying dried specimens by the hundreds. These specimens may have been collected all over the world, and by many different collectors. However, because they may never have studied the plants in living form, this second group are less apt to understand natural variations; in fact, such natural variations are usually dismissed by them as hybrids and hence are not to be considered as subjects in classification. They may dispense not only with the breeding behavior, chromosomal behavior, physiological behavior, and pathological behavior, but they may even dispense with seeing the living plants. Let us call them the "Classical Guys".
"Classical Guys" have done a great service in the naming of plants. For example they have found instances where two previously named species were actually only one species, as for example Rhododendron bullatum and R. edgeworthii that were similar in all respects and hence were merged into one species. These duplicates may have occurred in past years by pure accident or by design. We have been told that early plant explorers were paid a bonus for each new species they collected, and hence there was a profit motive in creating new species. Whether this is fact or fiction is not pertinent; the fact is that duplicate species names have occurred and the "Classical Guys" have merged these duplicates with great effectiveness. In this capacity they must be recognized for their contributions in plant classification, though perhaps on a different level than the "Good Guys".
We then come to the third group of classifiers, those who comb through botanical literature with great zeal. They delight in obscure and obsolete literature, long overlooked and forgotten. They can usually read ancient languages and decipher old manuscripts with ease. Their goal in life is to find an error that has been made by some of the "Good Guys" or "Classical Guys" in the past. Once an error is found it becomes the basis for the publication of a paper. These classifiers are the "Publishing Guys".
Like the early explorers who brought home new species, this group of classifiers has a profit motive in publishing papers. It is too, too true the merits of many of our scientists are judged by the numbers of papers they write, while overlooking the quality. In the present-day system the motto is heard "publish or perish". Hence the quantity of papers sometimes takes precedence over quality. It follows therefore when a scholarly paper can be written by the "Publishing Guys" on a mistake in classification, there is a strong economic motive to do so. It can readily be understood that the "Good Guys" and the "Scholarly Guy"” in the early days of botanical classification were involved in a superhuman task of dividing and naming the whole of the plant kingdom. They were driven by the overwhelming weight of the task into something less than perfection. The "Publishing Guys" jump on these errors with the same alacrity that buzzards in the jungles fall upon the carrion left by the king of beasts.
It is one of these "Publishing Guys" who is now proposing the change of R. japonicum into R. metternichii . It is the "Publishing Guys" who have accounted for many, if not most, of the recent name changes that have kept the plant world in a seething turmoil with little regard to the consequences of name changes.
Consequences of Name Changes
Plant names are deeply woven into the close-knitted fabric of the plant world. Name changes go far beyond the mere change in an encyclopedic description of plants. They affect all sciences and industries having to do with plants.
The exact identification of plants is critical to a plant pathologist who may be using that plant as an indicator for viruses. It affects a nurseryman who must assure his customers that all plants sold are true to name. It affects a geneticist who is counting chromosomes and must identify the plant precisely if his work is to be validated by fellow geneticists. It affects the pharmacologist who must guarantee that his product is safe and is properly labelled. It affects plant societies whose primary interests are the enrichment of a particular genus. It affects the average gardener because it creates confusion and frustration in his attempt to know the names of the plants he grows.
If the consequences were only botanical, we could leave the sole decision-making process to the botanists. However, with so many other groups having a vital concern in name changes, the base-line of decision-making must be broadened. And above all, a plant name change should not be considered for its value as the subject of a new scientific paper. With this in mind, let us consider further the case for constancy of names, and especially the principle of conserved names.
The Principle of Conserved Names
A conserved name may be defined as one that can never again be changed. The principle of conserved names is as old as the Linnaean system of Latin binomials itself. For example it was agreed by the botanical world soon after 1753 to begin binomial nomenclature of higher plants with the first edition of Linnaeus' Species Plantarum. By this momentous decision all name changes were, for the most part, delimited to the names given by Linnaeus in 1753. Likewise, genera names were conserved to those in his 5th Edition of Genera Plantarum. In general then, name changes could not go back further than 1753.
Likewise the principle of conserving generic names has been applied by the international botanical groups in recent times. Thus, as indicated earlier, the genus Loiseleuria became a nomina generica conservanda , or conserved genus name, in the First International Congress in Vienna in 1905. There is a sizable list of conserved genera.
What is needed badly today is a list of conserved species names. Certainly the International Code of Nomenclature is flexible enough to provide for the conserving of species names that have remained unchanged for let us say a period of 50 years or longer. There should be some provision to save the world of plant science and plant industry from the more or less irresponsible "Publishing Guys".
The Primary Offending Rule
The exact rule in the Code of Nomenclature that should be especially singled out is the so-called "homonym rule", or dual naming, as mentioned earlier. A species homonym is the use of a name for two different species in a genus. The present Code states that "Two species in the same genus cannot bear the same specific name."
As first adopted, the rules provided some flexibility. This flexibility would provide that a name need not be rejected because of an earlier homonym if that homonym was regarded as non-valid . The earlier homonym could be considered non-valid if it was forgotten, improperly described, improperly published, or otherwise out of general use.
It was the Americans who insisted that a name be rejected when that name is previously preoccupied (i.e. a homonym). The American-sponsored rule allows for no exceptions. In my view the Americans were wrong, and the Code should revert to acceptance of the original flexible rules. Our case for constancy of plant names rests largely on this one point, and we would hope that names that have been in general use for several generations could, and should be, conserved.
The frequent name changes based upon obsolete literature cast an unfavorable reflection upon the entire system of plant classification. They complicate literature and literature citations with no corresponding increase in clarity of plant classification.
Changes in species names, especially those under the homonym rule, affect the entire area of plant sciences and plant industries, and such changes must be weighed in the light of their consequences. We believe that nomenclature should rest on truth in classification of plants and less on printed regulations. In our view it is the existing rules that need changing, not the names. Let us hope that the followers of Linnaeus will make nomenclature a matter of clarity in classification of plants, not an exercise in formulation of rigid rules.