Issue 19 February 2013

What’s in a name? (Taxonomy, nomenclature, binomials, families, species, and the confusing world of plant classification) Mynou de Mey, Certified Aromatherapy Educator Master Herbalist

When I first studied Herbology, I found myself confronted with how scientific and complex the world of Nature was. And yet, without understanding our world correctly, we cannot conduct proper studies or identify plants correctly so that we can provide the care we are trained to do with knowledge and professionalism.

What is Botanical Nomenclature? Botanical nomenclature (in the form of binomials) is the formal, scientific naming of plants. It is related to, but distinct from, taxonomy. Plant taxonomy is concerned with grouping and classifying plants; botanical nomenclature provides names for the results of this process. Botanical nomenclature is governed by the International Code of Nomenclature for algae, fungi, and plants (ICN), which replaces the International Code of Botanical Nomenclature (ICBN).

Botanical nomenclature has a long history, going back to the period when Latin was the scientific language throughout Europe, and perhaps further back to Theophrastus. A key event was Linnaeus’ adoption of binomial names for plant species in his Species Plantarum (1753). Every plant species is given a name that remains the same no matter what other species are placed in the genus, and this separates taxonomy from nomenclature. These species names, together with names for other ranks (such as family, class, order, variety), can serve to express a great many taxonomic viewpoints.

In the 19th century it became increasingly clear that there was a need for rules to govern scientific nomenclature, and initiatives were taken to produce a body of laws. These were published in successively more sophisticated editions. For plants the key dates are 1867 (lois de Candolle), 1906 (International Rules of Botanical Nomenclature, ‘Vienna Rules’) and 1952 (International Code of Botanical Nomenclature, ‘Stockholm Code’). The most recent is the Vienna Code, adopted in 2005.

Botanical nomenclature, also known as binomial or binary nomenclature, gives each plant a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages. Such a name is called a binomial name (which may be shortened to just “binomial”), a binomen or a scientific name; more informally it is also called a Latin name. The first part of the name identifies the genus to which the species belongs; the second part identifies the species within the genus. For example, humans belong to the genus Homo and within this genus to the species Homo sapiens.

The value of the binomial nomenclature system derives primarily from its economy, its widespread use, and the uniqueness and stability of names it generally favors:

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Economy. Compared to the polynomial system which it replaced, a binomial name is shorter and eas- ier to remember. It corresponds to the widespread system of family name plus given name(s) used to name people in many cultures. Widespread use. The binomial system of nomenclature is governed by international codes and is used by biologists worldwide. Clarity. Binomial names avoid the confusion that can be created when attempting to use common names to refer to a species. Common names often differ even from one part of a country to an- other, and certainly vary from one country to another. Uniqueness. Provided that taxonomists agree as to the limits of a species, it can have only one name that is correct under the appropriate nomenclature code, generally the earliest published if two or more names are accidentally assigned to a species. However, establishing that two names actually refer to the same species and then determining which has priority can be a difficult task, particu- larly if the species were named by biologists from different countries, so that in reality, a species may have more than one regularly used name (these are “synonyms”). Stability. Although stability is far from absolute, the procedures associated with establishing binomial names tend to favor stability. For example, when species are transferred between genera (as hap- pens often as a result of new knowledge), if possible the second part of the binomial is kept the same.

What is Taxonomy? Taxonomy is the science of naming, describing and classifying organisms and includes all plants, animals, and microorganisms of the world. Taxonomists identify, describe, and arrange species into classifications, including those that are new to science. Taxonomy identifies and enumerates the components of biologi- cal diversity pro-viding basic knowledge. In the past 250 years of research, taxonomists have named about 1.78 million species of animals, plants, and micro-organisms, and yet the total number of species is un- known and probably between 5 and 30 million.

Taxonomists provide unique names for species, which can help us find out more about them and enable us to be sure that we are all talking about the same thing. Of course, there are names for organisms in many languages, but it is important, for example, when discussing the hedgehog to know whether one is talking about the small spiny insectivore Erinaceus europaeus, other members of the same family, cacti of the genus Echinocerus, or the orange fungus Hydnum repandum, all of which have the same ‘common’ name in English. For this reason the Latin ‘scientific’ name, is given as a unique, universal identifier.

How are Plants Classified? Biological classification is a method of scientific taxonomy used to group and categorize organisms into groups such as genus or species. These groups are known as taxa (singular: taxon).

Plants are classified in several different ways, and the further away from the garden we get, the more the name indicates a plant’s relationship to other plants and tells us about its place in the plant world rather than in the garden. Usually, only the Family, Genus, and species are of concern to the gardener, but we sometimes include subspecies, variety, or cultivar to identify a particular plant.

Starting from the highest category, plants have traditionally been classified as follows. Each group has the characteristics of the level above it but has some distinguishing features. The further down the scale you go, the more minor the differences become, until you end up with a classification which applies to only one plant.

Issue 19 Page 3

Even though it is important to know all that we can from the world of plants, we will concentrate on what is commonly studied in various Aromatherapy schools, such as: Family, Genus, Species, and Variety.

Family. Each Order is divided into Families. These are plants with many botanical features in com- mon, and this is the highest classification normally used. At this level, the similarity between plants is often easily recognizable by the layman. The number of plant families varies according to the bota- nist whose classification you follow. Some botanists recognize only 150 or so families, preferring to classify other similar plants as sub-families, while others recognize nearly 500 plant families. A widely-accepted system is that devised by Cronquist in 1968, which is only slightly revised today. The names of the families end in –aceae.

Genus. This is the part of the plant name that is most familiar, the normal name that you give a plant, such as Lavendula (lavender), Rosmarinus (Rosemary), and so on. The plants in a Genus are often easily recognizable as belonging to the same group. The name of the Genus should be written with a capital letter, i.e. Lavendula angustifolia. Together, the Genus and species name refer to only one plant, and they are used to identify that particular plant. Sometimes, the species is further divided into sub-species that contain plants not quite so distinct that they are classified as Varieties.

Species This is the level that defines an individual plant. Often, the name will describe some aspect of the plant, such as the color of the flowers or size or shape of the leaves, or it may be named after the place where it was found. Together, the Genus and species name refer to only one plant, and they are used to identify that particular plant. Sometimes, the species is further divided into sub-species that contain plants not quite so distinct that they are classified as Varieties. The name of the species should be written after the Genus name, in small letters, with no capital letter, i.e. “angustifolia”.

Variety A Variety is a plant that is only slightly different from the species plant, but the differences are not so insignifi-cant as the differences in a form. The Latin is varietas, which is usually abbreviated to var. The name follows the Genus and species name, with var. before the individual variety name, i.e. Cit- rus aurantium, var. amara.

References Barkworth, M. (2004), Botanical Nomenclature (Nomenclature, Names, and Taxonomy), University of Utah, archived from the original on 2011-02-20, http://www.webcitation.org/5wdX3kH4m, re- trieved 2011-02-20

McNeill, John; Barrie, F.R.; Burdet, H.M. et al., eds. (2006), International code of botanical nomen- clature (Vienna Code) adopted by the seventeenth International Botanical Congress, Vienna, Austria, July 2005 (elec-tronic ed.), Vienna: International Association for Plant Taxonomy, http://ibot.sav.sk/ icbn/main.htm, retrieved 2011-02-20 McNeill et al. 2006, Principle IV Congratulations to the most recent newly registered aromatherapists:

Jeong Hee An Ji Yeon Kang Hang Suk Lee Eun Mi Park Antonia V. Brasted Jiyoun Kim Mia Lee Da Eun Song Linda D. Hohmeister Mee Jeong Kim Hyun Min Lim Dayoung Song Dawn M. Johnson Seon Ju Kim Davina J. Mulimbi Sun Kyung Yu Choong Hwan Kang Si Nae Kim Seokhoon Nam

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