Abstract
Most changes in Latin names of pathogens result from research in systematic botany, microbiology, mycology, and nematology. Name changes are made according to, and often because of, international rules of nomenclature. New names for familiar organisms may be rejected on scientific or nomenclatural bases but should not be rejected merely because mastery of new names is inconvenient. A table of name changes proposed or adopted for tree pathogens is presented.
Changes in the Latin names of tree pathogens sometimes vex plant pathologists as well as tree care specialists. It may be incovenient to learn new names for familiar organisms, but this learning is necessary if one is to keep up to date professionally. Often, however, users of Latin names remain unaware of proposed changes or do not know why, where, or by whom the proposals were made. Thus many proposed changes do not receive timely consideration. While gathering information for a reference book about diseases of trees and shrubs (74), I noticed hundreds of changes that have been proposed for the names of tree pathogens. Adoption of many of the new names has been slow (decades in some cases), partly because the changes have occurred since previous reference books on plant diseases were prepared, and partly because nomenclatural changes are often published inconspicuously in journals and paper series devoted entirely to taxonomic research. The purpose of this paper is to promote the consideration of new names by describing the most common situations that necessitate name changes and by presenting a compilation of proposed changes.
People who change the names of plant pathogens usually have substantial reasons for doing so. These reasons fall into one or more of six categories: 1) The pathogen is reclassified in a different genus. 2) A group of similar species is consolidated under one species name. 3) A heterogeneous species is divided into several new species. 4) The sexual state is discovered for a fungal pathogen that was previously known only in an asexual state. 5) An older validly published name for a species is discovered and under rules of nomenclature must be applied as the legitimate name. 6) The pathogen was originally misidentified.
Except for the sixth case, the naming and renaming of plants, animals, fungi, and prokaryotic organisms (bacteria and mollicutes) is governed by carefully crafted rules. Those for naming fungi, for example, are part of the International Code of Botanical Nomenclature, to which systematic botanists and mycologists adhere. This code is reviewed and updated from time to time at international botanical congresses. (Separate codes, similar in general operation, govern the naming of animals and prokaryotic organisms.) Because most tree pathogens are fungi, I will describe some of the most common provisions of the botanical code. Although it is lengthy (472 pages) and legalistic, the rules that most often affect names changes are relatively few and simple in principle. For exceptions and fine points, and especially for what the code really says, I refer readers to the code itself (84).
Some Key Provisions of the Code
When a species is first given a Latin binomial name, a valid description must be published and one or more preserved specimens deposited for posterity. The author’s name, which may be abbreviated, is appended to the Latin binomial. The second part of the Latin binomial (known as the final, or specific, epithet), together with the author’s name, is linked permanently to a type specimen. This specimen is one of those on which the description was based. It is deposited in a herbarium of the author’s choice, where other researchers can obtain it for examination. The linkage of epithet to specimen ensures that the new species name will be applied only to specimens similar to the type. Names without descriptions and type specimens are invalid.
For example, when the pine needle cast fungus now known as Lophoderlmium pinastri (Schrad. ex Hook.) Chev. was first described in 1799 by Schrader, he named it Hysterium pinastri, and he deposited a type specimen in a European herbarium. Chevallier transferred H. pinastri to his new genus Lophodermium in 1826. During the next 150 years, several other Lophodermium species that colonize pine needles were recognized, but none was as widespread and destructive as L. pinastri. When severe outbreaks of pine needle cast occurred in North America in the 1960s and early 1970s, however, studies of the lophodermia on pine needles showed three species to be present where only one had been thought to occur. The most damaging species infected first-year needles and caused them to die and drop early in the second year. The other two species infected older needles and caused little harm to the pines. Representatives of the three species were compared with the type specimen, and it turned out that one of the weak pathogens, not the virulent one, matched the old type specimen of H. pinastri. Most of the damage was being caused by a fungus that had not previously been described. The unimportant fungus kept the familiar name because of the linkage of name to type specimen. Thus Lophodermium pinastri, contrary to the beliefs of the previous century, came to be known as a weak pathogen that attacks only the oldest needles and causes insignificant defoliation. The newly recognized species, responsible for the long-known disease, was named Lophodermium seditiosum Minter et al. (54).
If a species is described and named more than once, the oldest validly published specific epithet has priority.
Consider, for example, the fungus that causes Dothistroma needle blight, also known as red band needle blight, of pines. The pathogen was described from Illinois in 1941 and was named Dothistroma pini Hulbary. This name was used for many years until taxonomic studies by Morelet revealed that the same fungus had been validly described in Europe in 1911 by Doroguine as Cytosporina septospora Dorog. (26). Because the fungus seemed to be most appropriately classified in Dothistroma, it became necessary to use the new combination Dothistroma septospora (Dorog.) Morelet (79). Note here and in the Lophodermium example that the name of the author who most recently reclassified the fungus has been added to the name of the original author.
No two genera of plants (including fungi under the code) may have the same name. In case of conflict, the older validly published name has priority, and the more recently named genus must be renamed. Similarly, no two species in the same genus may have the same name. If through ignorance a scientist gives to a newly described species a name previously used for another species in the same genus, the earlier name has priority, and the second species must be renamed. Also, if a species that was validly named within one genus is reclassified in a second genus where a different species already has the same final epithet, the reclassified species must be renamed. If the reclassified species has synonyms, the oldest one that will be legitimate in the new genus is the correct one. If the species has no available synonyms, a new name must be coined.
The fungus that causes a well known tip blight of pines and other conifers provides an example. A 1980 proposal (79) by Dr. Brian Sutton of the Commonwealth Mycological Bureau to transfer this fungus from the genus Diplodia to Sphaeropsis and to change its name from Diplodia pinea (Desm.) Kickx to Sphaeropsis sapinea (Fr.) Dykko & Sutton has been widely accepted. This reclassification was based on Sutton’s judgment that the fungus conforms adequately to the description of the genus Sphaeropsis. The eptithet pinea had to be abandoned because it had previously been applied to other fungi in Sphaeropsis. The oldest epithet that could legitimately be used was sapinea.
The priority of old names extends back to specific starting dates between 1753 and 1821 when the first major taxonomic references for plants and fungi were published. A fungal name published earlier than the starting date for the major taxonomic group to which the fungus belongs has no standing unless validly republished on or after the starting date. When the name of a fungus known since before 1753-1821 and reclassified one or more times is written in its complete form, it has four main elements: the Latin binomial, followed in parentheses by the name of the person who described the species before the starting date and the name of the person who first validly published the Latin name (separated by “ex” or simply by a colon), and finally the name of the person who most recently reclassified the species. The name of the first authority is only enclosed within parentheses when a later author reclassifies a fungus. Thus, in our first example, the long-known needle cast fungus is Lophodermlum pinastri (Schrad. ex Hook.) Chev.
Acceptance of Changed Names
It is one thing for a taxonomic researcher to reclassify a fungus or correct its name, but this change will not necessarily be adopted by other mycologists, by plant pathologists, or by lay people such as tree care specialists. Professor Richard Korf, a specialist in fungal systematics at Cornell University, makes clear to his students and colleagues that they are not obliged to accept every new name that mycologists propose for plant pathogens. You or I can reject a change or defer adopting it until we are convinced it is scientifically worthwhile or until people more knowledgeable than ourselves adopt it. But if we reject or defer the change, we should have defensible reasons for doing so. We should be able to say why we disagree with the person who proposed the change or why we will defer adoption.
I often hear or see colleagues reject name changes for inadequate reasons, usually that they simply prefer a familiar name and don’t want to be bothered learning a new one, let alone learning the reason for the change. To such people and to my students I put the following argument. If you as a professional person have completed a piece of research or other work and published the results, you want your report to be noticed and its contents—your facts and ideas—to be carefully considered by readers. You hope your ideas will be accepted as valid, but the main matter is fair consideration. You should extend to the taxonomic work of biologists the same consideration that you desire for your own work.
Authors of scientific papers in plant pathology sometimes mention important synonyms for pathogen names. This practice promotes awareness of proposed changes in names, and it can help reduce the delay before a proposed change is generally adopted or rejected. If this practice were more common, nonspecialists would more readily notice and adopt new names of plant pathogens.
The table below shows name changes proposed or adopted for many tree pathogens. Not all of the proposals are recent, however, because plant pathologists have in many cases been slow to notice the contributions of taxonomic researchers. Because of limited space in the table, authorities for names are omitted. They are given in the references.
Some name changes adopted or proposed for pathogens of trees and shrubs.
Footnotes
↵1 Adapted from a presentation given at the Massachusetts Tree Wardens, Arborists and Utilities Conference, Chicopee, MA, 11 March 1987.
- © 1987, International Society of Arboriculture. All rights reserved.
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