by Whit Gibbons

January 21, 2007

Q. How do scientists know when they have found a new species, one not already known to science? I thought we were losing species worldwide, but lately I seem to be reading a lot about one scientist or another discovering a new bird, bat, or tree.

A. We are indeed losing species worldwide, at a much faster rate than we discover new ones. That's not the focus of this column, but it is a truth we should not lose sight of.

The first step in discovering a new species is knowing which species have already been discovered. When ecologists travel to regions where they are not familiar with the plants and animals, they read field guides about the flora and fauna. Many of these guides have photographs, keys to species recognition, and descriptions of size, color, and general appearance. Ideally, the books also have information about geographic ranges and the ecology of species. Examining museum specimens to learn about variations among species in a taxonomic group is important, too.

To recognize that a species is new to science, you must be an expert in a particular taxonomic group. The most likely areas for new species discoveries are exotic, unpopulated regions, especially in the tropics. For example, within recent months a new species of bat was found in Madagascar, a new monkey in Tanzania, and a new plant (in the violet family) in Cameroon. The scientists describing the new species had to be familiar with the particular taxonomic group and know the characteristics of every known species in the world.

New species, particularly insects, continue to be discovered even in North America, but the numbers pale in comparison to tropical regions. Because most of the United States and western Europe have been surveyed extensively, truly new species of vertebrates are less likely to be discovered. However, the use of DNA and other genetic analyses has brought greater definition to the relationships among species, so a plant or animal once thought to be a single species may be redefined as two or more.

For example, a map in a U.S. field guide from the 1970s will show a single species of the slimy salamander (Plethodon glutinosus) occupying most of the eastern United States. Today, slimy salamanders are partitioned into 16 different species, with different ones occupying different parts of the former range, based on a gene identification technique known as electrophoresis. Although most of the "new" species cannot be distinguished from each other visually, they are genetically distinctive. These kinds of species descriptions, however, do not count as discoveries never before seen by humans.

A different use of genetic analyses "to discover a new species" can be found in the 2003 description of Chamberlain's dwarf salamander from the Carolinas. These tiny brownish creatures are distinguishable from most other salamanders by their small size and by having four toes on each hind foot instead of five. Since at least the 1980s, the dwarf salamander has been known by herpetologists to represent two distinct species, because one form has a bright yellow belly. However, no one had formally described them in a scientific journal using the "International Code of Zoological Nomenclature." The 2003 description used genetic evidence along with morphological traits to distinguish two species that were already known to be distinct.

Genetic analyses were also used this past year to confirm the discovery of a new species of lizard in the rainforests of Borneo. In this case, the scientists were not splitting an assumed single species into separate genetic units or giving official recognition to a species already recognized as having two distinct forms. This was a species of lizard never before seen by scientists. They used DNA analyses to determine who its closest lizard relative is, which turns out to be a distantly related lizard from the Philippines.

Species new to science will continue to be found as long as scientists look for them. But we must guard against the misconception that such species are new to the world. They are not. They have been here for millions of years. And it is up to us to ensure that both "old" and "new" species remain a part of our environment.

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