Large Cat Species Discovered : Scientists have discovered that two populations of tigrina previously thought to be one species do not, in fact, interbreed and thus are distinct, according to results published today in Current Biology.
“So much is still unknown about the natural world, even in groups that are supposed to be well-characterized, such as cats,” says the study’s lead author, Eduardo Eizirik of Pontifícia Universidade Católica do Rio Grande do Sul in Brazil.
“In fact, there are many basic aspects that we still don’t know about wild cats, [including] their precise geographic distribution and their diets.”
Eizirik’s results have implications for conservation efforts—particularly laws about poaching and the designation of national parkland. Such measures are often focused on individual species.
Recognizing the northeastern tigrina as distinct means that biologists will have to assess its conservation status and determine what steps need to be taken so that both species of tigrina can be adequately protected.
Ancient Interbreeding
Eizirik and colleagues weren’t looking to discover a new species. Instead, they were looking to understand the evolutionary history of what were thought to be three species of cat from the genus Leopardus:
The Pampas cat (Leopardus colocolo) looks like a large, heavy-set, long-haired house cat. It lives in the grasslands and scrublands of South America, from southern Argentina and Chile up through Peru and Ecuador along the western third of the continent.
Geoffroy’s cat (Leopardus geoffroyi) is roughly the same size as the Pampas cat, with a brownish-yellow or gray coat, black spots on its trunk, and dark bands across its tail and limbs. Like the Pampas cat, Geoffroy’s cat likes scrublands and lives throughout Argentina.
The tigrina (Leopardus tigrinus), also known as the oncilla or little spotted cat, lives throughout much of Central and South America. With a yellow-brown coat and black rosettes, the tigrina looks like a house cat-sized leopard. Scientists had previously identified four sub-populations of tigrina, including the southern tigrina, which lives primarily in Brazil’s mountainous forests, and the northeastern tigrina, which lives in savannahs and grasslands. The coat of the northeastern tigrina is slightly lighter, and the rosettes are sightly smaller, than those of its southern relative.
Eizirik and colleagues obtained DNA samples from a total of 216 different Leopardus cats across their ranges. Analysis of the DNA sequences found in the mitochondria, the cell’s power plant, revealed ancient interbreeding between the Pampas cat and the northeastern tigrina.
Since an individual only inherits mitochondrial DNA from its mother, researchers could peer into the ancient history of these two felines, and found that they mated together frequently before the two cats split into separate species.
Although the Geoffroy’s cat and the southern tigrina divided into separate species over a million years ago, they began to mate together in the more recent past in the areas of southern Brazil and Bolivia where their habitats overlap. While the two cats interbreed regularly at this contact zone, the mating doesn’t extend to farther areas and the two species remain distinct.