科學家用基因解釋了爲何大小熊貓都以竹子爲食
Chinese researchers said Monday they have uncovered the genetic basis of why giant pandas and red pandas have evolved independently to have shared features such as a bamboo-based diet and false thumb.
日前，來自中國的研究人員表示，他們已經發現了大熊貓和小熊貓的遺傳基礎，可以解釋爲什麼這兩種動物獨立進化，但是卻又具備喜食竹子和僞拇指等共同特點。Despite being classified as carnivores, both giant pandas and red pandas, which separately evolved from meat-eating ancestors and diverged from each other more than 40 million years ago, subsist almost entirely on bamboo -- a phenomenon termed convergent evolution, where similar traits arise in two unrelated or distantly related species.
大熊貓和小熊貓都是分別從食肉祖先進化而來，並且已經分開超過4000萬年。儘管這兩種動物都被歸類爲食肉動物，但是它們卻幾乎完全依賴竹子生存--這種現象被稱爲趨同進化，相似的性狀會在出現在兩個無關、或者關係較遠的物種身上。Additionally, both species possess a false thumb, which enables the animals to adroitly grasp bamboo.
此外，這兩個物種都具有僞拇指，這可以使它們熟練地抓住竹子。
To uncover the genetic basis of such convergence, Fuwen Wei and colleagues from the Institute of Zoology, part of the Chinese Academy of Sciences, sequenced the genome of a wild male red panda and compared it with the reassembled genome of the giant panda.
爲揭開這種趨同現象的遺傳基礎，魏輔文和他中國科學院動物研究所的同事們對野生雄性小熊貓的基因組進行了測序，並與大熊貓重新排列過後的基因組進行對比。Their findings were published in the recent issue of U.S. journal Proceedings of the National Academy of Sciences.
他們的發現被刊載在美國雜誌《美國國家科學院學報》最新一期上。The results confirmed that giant pandas belong to the family Ursidae together with polar bears, whereas red pandas belong to the superfamily Musteloidea together with ferrets and that the two species separated 47.5 million years ago, slightly earlier than previous molecular-based estimate of 43 million years ago.
結果證實，大熊貓和北極熊一樣屬於熊科，而小熊貓則和雪貂一樣屬於鼬科大家族，這兩個物種在大約4750萬年前分離，略早於先前根據分子估計的4300萬年。Genome analysis revealed signs of adaptive convergence in 70 genes, including two genes, known as DYNC2H1 and PCNT, that are involved in false thumb development.
基因組分析顯示70個適應性趨同的基因，包括兩個調控熊貓僞拇指發育的重要基因DYNC2H1和PCNT。Giant and red panda genomes also share 10 pseudogenes, or "false" genes, which look like real genes but have no apparent function.
大熊貓和小熊貓的基因組裏還共有10個假基因，這些基因看起來跟真的一樣，但是卻沒有明顯的功能。
