French wildlife rangers may have discovered a new species of fox-like cat, according to CNN. It’s said to be larger than a domestic cat and to have pronounced canine teeth. Both the definition and arrival of a new species bear review.
The CNN article stated that 16 of the cats have been spotted in remote areas of Corsica, off the coast of France, and that they loosely resemble both the European wildcat and African forest cat. DNA tests have definitively ruled out the new “cat fox” from belonging to either species. This examination has led to questions about what differentiates one species of life from another and how new species come to be.
Answering Evolution’s Biggest Vocabulary Question
What is a species? Two very unique-looking animals can be the same species and two nearly identical creatures can be different species, so where does evolutionary biology draw the line? In the 1940s, Harvard biologist Ernest Mayr came closest to answering this question. “Mayr proposed what has become known as the ‘biological species concept,'” Dr. Stephen Nowicki, Professor of Biology at Duke University, said. “The biological species concept defines a species as a population or a group of populations whose members have the potential to interbreed in nature and produce viable and fertile offspring, but who cannot successfully interbreed with other populations or other species outside that group.”
Dr. Nowicki said that in far simpler terms, “we define a species, specifically in population genetics terms, as the largest inclusive group of individuals among whom genetic exchange is possible.” In this sense, the distinction between two species resembles a considerable barrier inhibiting the exchange of genetic information in breeding. “The term we use for this is ‘reproductive isolation.’ German shepherds can breed quite easily with beagles but not with wolves, so the shepherd and the beagle are clearly the same species by this definition, while the wolf is distinct.”
However, there are rare exceptions to Mayr’s biological species concept. Dr. Nowicki mentioned two bird species—Lazuli buntings and indigo buntings—that can breed and whose hybrid offspring will survive and breed as well. He also cited as exceptions species that reproduce without sex and extinct species unable for study. Finally, he provided two alternative theories of classification that scientists use in conjunction with the biological species concept: the morphological species concept, which distinguishes between animal species by specifying identifiable morphological differences between them, and the phylogenetic species concept, which focuses on the distances between animals from their common ancestor to draw lines between two species.
The Origin of New Species
The other—and far easier—question of the day is, how do new species appear, and where do they come from? “If we take a look at the fossil record, we can actually see two different general patterns by which species appear,” Dr. Nowicki said. “On the one hand, we find examples in which a series of fossils obtained across different geological time periods appears to form a linear progression from one species to another with a series of intermediates that display a steady range of small changes in shape, size, or other defining characteristics. We call this pattern ‘anagenesis.'” In other words, a new species gradually replaces an old one over the course of many generations, based on things like natural selection.
The other method by which new species arise is called “cladogenesis” or “branching evolution.” Dr. Nowicki says this is when one ancestral species splits into two descendant species. He brought up the black-bellied seedcracker, a West African bird that either features a very large beak or a very small one, with few surviving examples in between. Dr. Nowicki said that, using Mayr’s biological species concept, the seedcracker is considered one species because of its population’s ability to mate and produce healthy offspring. If the large-beaked seedcrackers and small-beaked seedcrackers stopped mating with one another and only produced with seedcrackers of their own beak sizes, eventually they would split off and become two distinct species only capable of producing offspring with their respectively sized beaks.
France’s new cat fox probably faces years of evolutionary study before a determination of its origins and uniqueness can be made. However, it’s likely in the meantime that scientists will use one, two, or all three of the species concepts to classify it while examining possibilities of anagenesis and cladogenesis to explain its ancestors.
Dr. Stephen Nowicki contributed to this article. Dr. Nowicki is Bass Fellow and Professor of Biology at Duke University, as well as Dean and Vice Provost of Undergraduate Education at Duke. He earned his undergraduate degree and a master’s degree at Tufts University, and his Ph.D. from Cornell University.