Taxonomy: What's In A Name?
Have you ever thought about why we name things at all? If you have, you probably realized that names are very important for communicating information to others. If we all created our own names for plants or animals, we'd have no clue what anyone else was talking about. What about rolly-poly bugs? People in others areas may think of them as pill bugs or sow bugs. In the United States, we call both black vultures and turkey vultures buzzards. But in the United Kingdom, what they call buzzards are all the broad-winged hawks. Inconsistencies like these led to the creation of a system of naming things that allows scientists all over the world to communicate more precisely.
Swedish Naturalist Carl Linnaeus, 1707-1778
A man named Linnaeus came up with this system of describing and naming new species. Before Linnaeus' time, multiple common names weren't the only problem. Biologists described species with long, unwieldy Latin names. For example, the common wild briar rose was called Rosa sylvestris inodora seu canina by some and Rosa sylvestris alba cum rubore, folio glabro by others. Another problem was that names for species changed over time depending on the fancy of scientists.
[Text adapted from http://www.ucmp.berkeley.edu/history/linnaeus.html] Read more about Carl Linnaeus Carl Linnaeus: The father of modern plant and animal classifcation (1707-1778) [http://www.ucmp.berkeley.edu/history/linnaeus.html]
During the 1700s, naturalists on major collecting trips to Africa, Asia, and America returned to Europe with thousands of specimens. This large influx of new species made systematizing the naming process critical.
[Map courtesy of the Swedish Linnaeus Society Long-distance voyages of Linnaeus' Uppsala students, from Rob. E. Fries. Published in Svenska Linnesallskapets Arsskrift 33-34 (1950-51):31-40.]
Nineteen of Linnaeus' own students from the University of Uppsala went on exploration voyages: Daniel Solander traveled with James Cook collecting plants from Australia and the South Pacific, Anders Sparrman went on Cook's second voyage, and Pehr Kalm brought back plants from the American colonies. Each new specimen needed to be described and named. The specimen chosen as the basis of the first description of a new species was called the "type" specimen.
Binomial Naming System
After experimenting with several approaches, Linnaeus refined and standardized a binomial (double) naming system. He designated one Latin name to indicate the genus, and one as a "shorthand" name, or species epithet, for the species. Linnaeus picked Latin because it was the universal language of science, the only language that provided "mutual understanding...Such was the case with Linnaeus when in 1736 he visited London and met such eminences as Sir Hans Sloane, President of the Royal Society, whose magnificent collection was to form the nucleus of the British Museum, to whom he had to speak in Latin, having no English." [Jenkins, Alan C. "The Naturalists: Pioneers of Natural History." NY: Mayflower Books, 1978. p. 30-31]
The Binomial Name
Binomial scientific names are composed of the genus name and the species epithet (usually an adjective). The species epithet usually relates to some aspect of the species or to the person who found the original. For example, the scientific name for humans is Homo sapiens. (Genus Homo=man, specific epithet sapiens=thinking. Literally, in Latin, thinking man.)
Red Tree Frog Phyllomedusa callidryas
Likewise, the scientist who first described the Central American red-eyed treefrog thought it was especially pretty with its pea-green back, chrome-yellow and bright blue ladder patterns on its sides, bright orange feet, and vermillion eyes, and thus named it Phyllomedusa callidryas - the beautiful wood nymph (calli=beautiful and dryas=wood nymph)(image=redtreefrog.gif)
Linnaeus himself discovered over one hundred new species of plants during his expedition to Lapland in 1732 including the rare species Campanula serpyllifolia. It was later renamed Linnaea borealis by Gronovius, in honor of Linneaus' contribution to the fledging science of taxonomy: the system of identifying, naming, and classifying all livingorganisms.
Organisms that have the same genus name have similar features. For instance, all oak trees have the genus name Quercus. They all have acorns and clusters of buds at the tip of the branch. Likewise, poison ivy, Toxicodendron radicans, and poison sumac, Toxicocendron vernix, both have a chemical that causes an itchy allergic reaction. Winged sumac and mango are in the same family but not the same genus, and most people are not allergic to them.
Species but Not Quite Specific
The second part of the name is the species epithet. It specifies the exact organism in that genus, but the species name by itself is not very specific. For example, the Black bear, Ursa americanus; the Atlantic lobster, Homarus americanus; and the American toad, Bufo americanus, all have the species epithet americanus. If you told someone that you ate americanus for dinner last night, they wouldn't know if you meant a black bear, an American toad, or an Atlantic lobster! Combining the species epithet with the genus name clarifies your menu. Usually the species epithet describes the area where the organism is found, the name of the person who found it, or what it looks like, not necessarily what kind of organism it is.
Scientific Names are based on the concept of "Biological" Species
So What is a Species?
Ernst Mayr defines species as "groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups."
The biological species concept is the basis for naming species, but the vast majority of species were described without specific data on whether they could interbreed with some other group or not. The systematist who described them did so because the morphological/anatomical variation found in the population did not overlap with that found in other populations. The absence of overlap was evidence of non-interbreeding. As an example, if individuals in population "A" had 2-5 scales on part of its body and population "B" had 4-8 scales, there would be overlap in the range of 4-5 scales. If more than 25% of the individuals in both populations have 4-5 scales, the two populations are assumed to be the same species exhibiting normal variation. If 75% of the individuals in each population shows disparate scale numbers, i.e., 75% of population A has 2-3 scales and 75% of population B has 6-8 scales, the populations would be considered subspecies.
Image courtesy of Animals of the Arctic c1998 ERCHA
American black bearImage courtesy of Bear Country USA
For example, the Alaskan brown bear (Ursus arctos), the polar bear(Ursus maritimus), and the American black bear (Ursus americanus) are three different species. They are visibly similar and we would recognize them as bears, but since they do not interbreed with each other, they are three separate species.
Today, scientists increasingly view biological species through the perspective of evolutionary time and speciation events. Known as the Cladistic Species Concept, the basic idea behind cladistics is that members of a group share a common evolutionary history, and are "closely related", more so to members of the same group than to other organisms. These groups are recognized by sharing unique features which were not present in distant ancestors. These shared derived characteristics are called synapomorphies. Genetic sequencing provides a more precise measure of the genealogical relationships of organisms, and as a consequence it is a tool that frequently is used rather than relying solely on physical or behavioral characteristics. It can also be used for organisms that have non-sexual reproductive strategies such as bacteria.
The record below represents a partial sequence of mitochondrial DNA sequencing for the Puma concolor, commonly called Mountain lions, cougars or pumas. By comparing this pattern against similar species, researchers can tell how closely animals are related genetically.
BASE COUNT 126 a 88 c 78 g 90 t
[An example of gene sequencing]
ORIGIN1 tttgttccct aaatagggac ttgtatgaat ggccacacga gggctttact gtctcttact 61 tccaatccgt gaaattgacc ttcccgtgaa gaggcgggaa tacaacaata agacgagaag 121 accctatgga gctttaatta accgacccaa agagacccat caatttcaac cgacaggaac 181 aacaaacctc tgtatgggcc gacaatttag gttggggtga cctcggagaa cagaacaacc 241 tccgagtgat ttaaatcaag actaaccagt cgaaagtatt acatcactta ttgatccaaa 301 agtttgatca acggaacaag ttaccctagg gataacagcg caatcctatt tcagagtcca 361 tatcgacaat agggtttacg ac
It is this type of research that allows scientists to determine that the Florida panther is a subspecies. While the Florida panther is related to mountain lion populations of the West, it has been reproductively isolated from those populations. While they can still interbreed, genetic analyses show marked differences between the Florida panther and the mountain lion. Thus the Florida panther is considered a subspecies, Puma concolor coryi.
Read more about the Biological species.
Taxonomy: Name Game Rules
The science of naming organisms is called taxonomy. While it can get very complicated, the following basic rules apply:
- No two different species can have the same combination of genus and specific names.
- No species is given more than one combination of genus and specific name.
- Genus name is always capitalized & italicized or underlined.
- Specific epithet is not capitalized, but is always italicized or underlined.
Where are we in the Name Game?
Taxonomists have been relatively busy since Linnaeus' time. Over 1.5 million species have been named and described. However, it is estimated that as many as tens of millions of species have yet to be discovered. Many of these are in remote parts of the world-in the Mayan forests of Belize and the mountains of Burma.