眾所周知,，現(xiàn)今的狗是由古代的狼演變來的,，但美國斯坦福大學的一項新研究表明情況恰恰相反，至少現(xiàn)今的一些狼披著狗的外衣,，繼承了古代的狗的一些特征,。灰狼因其顏色而被命名為灰狼,。但北美的許多狼是黑色而不是灰色,。負責此項研究的斯坦福大學的喬治·S·巴什表示，產(chǎn)生黑色皮毛的基因突變最早出現(xiàn)在狗身上,，之后因狼與狗雜交,，從而使這一外表特征由狗傳給了狼。
研究人員表示,，黑狼幾乎是北美的特有品種,，且更多的黑狼生活在森林地區(qū)。實際上,，森林中的黑狼占整個黑狼數(shù)量的62%,，相反，在開闊的凍原地帶，黑狼只占7%,。但巴什表示,，野生動物生物學家認為狼沒有過多地依賴保護色生存，“這可能還發(fā)生了其它事情,。這是一種直觀的吸引力,，當你看到動物和周圍環(huán)境渾然一體時，就會覺得特別地美,。這一點可以由自然選擇來加以解釋,，這能使它們更好地偽裝成捕食動物或獵物。”然而,，狼沒有太多的捕食大敵,，也沒有證據(jù)表明黑色皮毛能加大狼捕獲獵物的可能性。
巴什表示,，像人類一樣,，黑狼隨著衰老也會導致毛發(fā)由黑色變成灰色。因此你會想到如果黑色皮毛突變是由自然選擇而來的,，它就應(yīng)該一直都是黑色的,，而不會因衰老而變成灰色。
研究發(fā)現(xiàn),，決定狗不同顏色的皮毛的蛋白和人類體內(nèi)消炎和抗感染的蛋白是一樣的,。此研究報告的另一作者安德森表示，數(shù)千年以來,，人類就已經(jīng)培育出了黑色皮毛的家用狗。她說：“不過,，如今,，我們不僅看到野狗也有黑色皮毛，還發(fā)現(xiàn)黑色皮毛對狗非常有利,。”基因測試表明,，黑色皮毛的基因突變大約是在過去1-1.5萬年間由狗傳給狼的。雖然這是意外事件,，但黑狼首次表明狼這種動物也經(jīng)受了人類的基因改良,。（生物谷Bioon.com）
生物谷推薦原始出處：
Science Published Online February 5, 2009 DOI: 10.1126/science.1165448
Molecular and Evolutionary History of Melanism in North American Gray Wolves
Tovi M. Anderson 1, Bridgett M. vonHoldt 2, Sophie I. Candille 1, Marco Musiani 3, Claudia Greco 4, Daniel R. Stahler 5, Douglas W. Smith 6, Badri Padhukasahasram 7, Ettore Randi 4, Jennifer A. Leonard 8, Carlos D. Bustamante 7, Elaine A. Ostrander 9, Hua Tang 1, Robert K. Wayne 2, Gregory S. Barsh 1*
1 Departments of Genetics and Pediatrics, Stanford University, Stanford, CA 94305, USA.
2 Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 91302, USA.
3 Faculty of Environmental Design, University of Calgary, Calgary AB, T2N1N4, Canada.
4 Istituto Nazionale per la Fauna Selvatica (INFS), 40064 Ozzano Emilia (BO), Italy.
5 Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 91302, USA.; Yellowstone Center for Resources, National Park Service, Yellowstone National Park, WY 82190, USA.
6 Yellowstone Center for Resources, National Park Service, Yellowstone National Park, WY 82190, USA.
7 Department of Biological Statistics and Computational Biology, Cornell University, Ithaca, NY 14853, USA.
8 Department of Evolutionary Biology, Uppsala University, 75236 Uppsala, Sweden.
9 National Human Genome Research Institute, Bethesda, MD 20892, USA.
Morphologic diversity within closely related species is an essential aspect of evolution and adaptation. Mutations in the Melanocortin 1 receptor (Mc1r) gene contribute to pigmentary diversity in natural populations of fish, birds, and many mammals. However, melanism in the gray wolf, Canis lupus, is caused by a different melanocortin pathway component, the K locus, that encodes a beta-defensin protein which acts as an alternative ligand for the Mc1r. We show that the melanistic K locus mutation in North American wolves derives from past hybridization with domestic dogs, has risen to high frequency in forested habitats, and exhibits a molecular signature of positive selection. The same mutation also causes melanism in the coyote, Canis latrans, and Italian gray wolves, and hence our results demonstrate how traits selected in domesticated species can influence the morphologic diversity of their wild relatives.
