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.
本周一中國研究人員表示說他們已經發現了大熊貓和紅熊貓的遺傳基礎，可以解釋為什麼這兩種動物獨立進化，但是卻又具備喜食竹子和假拇指等共同特點。
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.
大熊貓和紅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為食肉動物，但是它們卻幾乎完全依賴竹子生存——這種現象被稱為趨同進化，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，這兩個物種都具有假拇指，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. Their findings were published in the recent issue of U.S. journal Proceedings of the National Academy of Sciences.
為揭開這種趨同現象的遺傳基礎，傅文偉(音)和他中科院動物研究所的同事們對野生雄性紅熊貓的基因組進行了測序，並和熊貓重新排列過後的基因組進行對比。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(Ursidae)，而紅熊貓則和雪貂一樣屬於鼬科(Musteloidea)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個基因具有自適應收斂的跡象，包括有關長出假拇指的兩個基因DYNC2H1和PCNT。
Further, enzymes involved in dietary protein digestion and amino acid utilization as well as proteins involved in vitamin metabolism and absorption showed signs of adaptive convergence, suggesting that these genes may have similarly evolved to support and supplement a bamboo-based diet.
此外，涉及到膳食蛋白質消化和胺基酸利用的酶、以及維生素代謝和吸收的蛋白質也顯示出了自適應收斂的跡象，這表明這些基因可能已經相識地進化到可以支持和補充這兩種動物以竹子為基礎的食譜。
Giant and red panda genomes also share 10 pseudogenes, or "false" genes, which look like real genes but have no apparent function.
大熊貓和紅熊貓的基因組裡都有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。
Notably, the TAS1R1 gene, which enables carnivores to taste meat’s umami flavor, has been pseudogenized in both pandas, reflecting the animals』 shift from carnivory to omnivory and, ultimately, herbivory.
值得注意的是，兩種胖達體內的TAS1R1基因(這種基因使得肉食動物可以嘗到肉的鮮味)都已經變成了假基因，這反映這兩種動物從食肉動物變成了雜食性動物，並最終變成食草動物。
"Our findings provide rich insights into genetic convergence mechanisms underlying phenotypic convergence and adaptation to a specialized bamboo diet in both pandas," the researchers wrote in their paper.
研究人員們在他們的論文中寫道：「我們的發現為兩種胖達表型趨同和喜食竹子現象之下的遺傳趨同機制提供了豐富的洞察。」
（編輯：何瑩瑩）