For the first time, scientists have sequenced the genome of a tiger. And not just any tiger, but a Siberian tiger – the world's largest living felid. The researchers' just-published report includes a comparative analysis of the sequence with those of several other big cats, revealing molecular signatures for adaptations ranging from the Siberian Tiger's strength, to the snow leopard's predisposition to high-altitude living.
Above: A Siberian tiger at the Walter Zoo in Gossau, Switzerland | Photo Credit: Tambako via flickr
The report, which appears free of charge in the latest issue of Nature Communications, is the first to examine the whole genome sequence of "big" cats – that is, cats from the genus Panthera. Such analyses have previously been limited to the genomes of the domestic housecat, Felis catus.
The international research team cross-referenced gene clusters from seven mammalian genomes, including tiger, cat, human, dog, mouse, giant panda and opossum. The Venn diagram of their results, featured above, reveals something we know from previous studies to be true of gene families, namely that there is a LOT of overlap between species; the researchers identified over 14-thousand gene families that were shared by all seven mammalian species, and a mere 103 shared exclusively by the tiger and cat.
Of course, the stretches of genome that don't overlap are frequently the most interesting, as they've been known to form the genetic basis for unique physiological or behavioral characteristics. A comparison of the Siberian tiger genome with those of the African lion, white African lion, snow leopard and white Bengal tiger, for example, revealed a trove of "genetic signatures that may reflect molecular adaptations consistent with the big cats’ hypercarnivorous diet and muscle strength... a snow leopard-specific genetic determinant... which is likely to be associated with adaptation to high altitude... [and] a mutation likely responsible for the white lion coat colour." The researchers also identified evidence for especially rapid evolution in the Siberian tiger for muscle strength and energy metabolism.
Not exactly surprising findings, per se, but it's exciting and obviously important to get a lay of the big cats' genetic landscapes. These animals, after all, may not be around much longer outside of zoos and nature reserves. As the researchers note:
It is postulated that without conservation measures tigers will soon become extinct in the wild, thus turning the preservation of existing wild tiger populations into a major goal of conservation efforts. Tigers comprise of nine genetically validated subspecies. Four of these went extinct in the wild during the last century (Javan, Balinese, South China and Caspian tigers), leaving five extant subspecies (Amur, Bengal, Indochinese, Malayan and Sumatran tigers).