by Whit Gibbons

January 14, 2007

Q. I have two questions. How do scientists know when they have discovered a "new" species, and how do they decide what to name it?

A. This column answers the question about scientific names. How scientists recognize that a species is new to science will be addressed in next week's column.

Have you ever seen a Daucus carota? This is not a new Italian car, and you have not only seen one but also probably eaten one. Daucus carota is the scientific name for a carrot. Why don't we just call it a carrot?

One purpose of scientific names is to provide a partial taxonomic map to the evolutionary relationships among species of plants and animals. The chosen names confirm our understanding of the origins and levels of kinship among different species. They also help maintain uniformity in what species are called.

The system is not perfect, but scientific names provide consistency and a level of accuracy in biology that are often lacking when only the common names are used for organisms. For example, for an ecologist writing about the primitive fish variously called bowfin, cypress bass, or dog fish, the name Amia calva unmistakably identifies the species. By the "rules of scientific nomenclature" only one species in the world can be given that name. Scientists known as taxonomists spend a lot of time making sure the rules are not broken.

Every species of animal or plant has two scientific names. The first name, the genus, is always capitalized; the second, which identifies the species within the genus, is not, even when it is derived from a proper name. Both these names are italicized. A genus may comprise several closely related species. Thus many large hawks are placed in the genus Buteo. The genus Anopheles includes the only species of mosquitoes that transmit malaria. Just as closely related species are placed in the same genus, closely related genera (the plural of "genus") are grouped into a family. Jaguars, tigers, and house cats all belong to the family Felidae. Skunks, otters, and badgers are in the family Mustelidae.

The names are usually of Latin or Greek origin or at least are made to look like they are. Some names are chosen to represent a definitive feature of the organism. For example, the Sonoran mountain kingsnake, a beautiful red-, white-, and black-ringed creature, is called Lampropeltis pyromelana. The genus name means "beautiful shield" in Greek, and the species epithet means "black fire." Some species names were not well chosen, as observed in the black racer (Coluber constrictor), which was named in the 1700s in Europe from a museum specimen collected in North America. Racers are not constrictors, but the name persists.

How closely we are associated with a species can determine what we call it on an everyday basis. Ichthyologists who study the freshwater fishes called darters refer to most by their scientific names. However, the use of a common name may take precedent when a species achieves some level of popularity or notoriety with the general public, as did the snail darter, Percina tanasi. But pet owners do not say their Canis familiaris barks too much or their Felis domesticus meows to be fed. Or imagine a cowboy running into the saloon and yelling at the men to drink down their whiskeys and saddle up because the herd of Bos taurus is stampeding. Some species, however, are commonly known by their scientific name, such as Alligator, Iris, and Gorilla.

Some scientific names are used to designate where a species was first discovered or to honor someone. The genus name for milkweeds is Asclepias, after the Greek demigod of medicine. The species name of the threatened species known as the Alabama red-bellied turtle is Pseudemys alabamensis.

The order achieved by adhering to the rules of scientific nomenclature is important in biology. The names are intended to tell us something based on our knowledge of ecology and evolution. And acquiring knowledge is certainly an appropriate endeavor for Homo sapiens, whose species name, derived from Latin, means "knowing, wise." Some members of this species, however, make us wonder if this is one of those names that should be in the "not well chosen" category.

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