Southern tigrina : A new species

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Southern tigrina (Photograph : Tadeu Oliveira)

Member of the subfamily Felinae the southern tigrina (Leopardus guttulus) is found in southern and southeastern Brazil. This spotted feline has been hiding in plain sight for many years, but in 2013 it was recognized as a distinct species. For decades, this South American cat was considered to belong to the Oncilla (L. tigrinus), also known as the tiger cat, little spotted cat or tigrillo.

Perfect example of cryptic species

Initially it was believed that there is only one species of Brazilian tigrina, but when genetic studies were conducted a vast difference was found between the populations of northeastern Brazil and those found in southern Brazil. The southern tigrina is almost impossible to differentiate from its northeastern counterpart, with extremely subtle clues to show they are two distinct species. The northeastern tigrina has a lighter pelt, smaller spots and a longer tail, with barely perceptible variations in ear shape.

While investigating, the researchers studied the genetic dissimilarities of tigrinas throughout Brazil and found vast differences. On decoding the DNA sequences of 74 Leopardus geoffroyi, 27 Leopardus colocolo and 115 Leopardus tigrinus, researchers found startling and unprecedented differences between tigrinas of the south and southeast on one hand and the northeast on the other; most of the differences were as significant as those discovered between other species of wild cats. After the discovery scientists gave the established tigrina name (Leopardus tigrinus) to northeastern cats, while the new name (Leopardus guttulus) has been assigned to the southern populations.

These feline represent cryptic species (where a single species actually turns out to be two or more), involving two biological groups that are considered to be almost morphologically identical, each of which are capable of interbreeding.

The latest study also proved an intricate, evolutionary connection between the tigrinas and two other species of neotropical cat. According to the records wild cats had a history of hybridization. Earlier, researchers believed that mating took place only between genetically different individuals, hailing from two utterly distinct species. For instance, they found hybridization and transmission of genes between the pampas cat (Leopardus colocolo) and the northeastern tigrinas (Leopardus tigrinus). Now the new fact that has come to light shows, at the margins of its range, the newly recognized southern tigrinas (Leopardus guttulus) interbreeds with Geoffroy’s cats (Leopardus geoffroyi), but it does not seems to interbreed with the oncilla or the northeastern tigrinas (L. tigrinus).

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Physical characteristics

Going by the appearance, the southern tigrina can be differentiated from the oncilla (L. tigrinus) by its somewhat darker background coloring, bigger rosette pattern, and a little shorter tail. Southern tigrina has a yellowish-ocre coat patterned with open black rossettes. Nevertheless, it is very hard to differentiate between the two species by appearance alone, since more genetic variation tends to occur within each species than between the two species.

Considered to be endemic, or only one of its kinds to a defined geographical location, the species is threatened because its habitat, the Atlantic Forest, is disappearing fast. It’s a terrestrial Biome (geographically and climatically defined as contiguous areas with similar climatic conditions) and region that stretches along the Atlantic coast of Brazil from Rio Grande do Norte state in the north to Rio Grande do Sul state in the south, and inland as far as Paraguay and the Misiones Province of Argentina.

At present, efforts are being focused to better understand the genetics, ecology, biodiversity and evolution of southern tigrina to devise more effective conservation strategies. Besides, more studies are being undertaken throughout South America to better understand the special differences between the southern tigrina and its close cousin oncillas.

Why oncillas and southern tigrinas do not interbreed ?

In ecology, speciation, an evolutionary process by which new biological species arise, is an ongoing natural process. A demographic expansion following the last Ice Age (20,000 years ago) is thought to have led to the allopatric speciation of southern tigrinas. This speciation occurs when biological populatons of the same species become isolated from each other to an extent that prevents or interferes with genetic interchange. In this case it is believed that probably due to habitat differentiation, interbreeding could not take place between oncillas and southern tigrinas. While on the other hand, hybridization and gene flow occurs between southern tigrinas and Geoffroy’s cats in southern Brazil at their contact zone or “hybrid swarm”—an area where more or less all southern tigrinas and Geoffroy’s cats are partial hybrids of the two.

Interestingly all the hybrids are clearly fertile and there are still strong genetic difference between the two species in parts of their range outsided the contact zone. Scientists strongly believe that they are not going to merge back into a single species.

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