众所周知，现今的狗是由古代的狼演变来的，但美国斯坦福大学的一项新研究表明情况恰恰相反，至少现今的一些狼披着狗的外衣，继承了古代的狗的一些特征。灰狼因其颜色而被命名为灰狼。但北美的许多狼是黑色而不是灰色。负责此项研究的斯坦福大学的乔治·S·巴什表示，产生黑色皮毛的基因突变最早出现在狗身上，之后因狼与狗杂交，从而使这一外表特征由狗传给了狼。
研究人员表示，黑狼几乎是北美的特有品种，且更多的黑狼生活在森林地区。实际上，森林中的黑狼占整个黑狼数量的62%，相反，在开阔的冻原地带，黑狼只占7%。但巴什表示，野生动物生物学家认为狼没有过多地依赖保护色生存，“这可能还发生了其它事情。这是一种直观的吸引力，当你看到动物和周围环境浑然一体时，就会觉得特别地美。这一点可以由自然选择来加以解释，这能使它们更好地伪装成捕食动物或猎物。”然而，狼没有太多的捕食大敌，也没有证据表明黑色皮毛能加大狼捕获猎物的可能性。
巴什表示，像人类一样，黑狼随着衰老也会导致毛发由黑色变成灰色。因此你会想到如果黑色皮毛突变是由自然选择而来的，它就应该一直都是黑色的，而不会因衰老而变成灰色。
研究发现，决定狗不同颜色的皮毛的蛋白和人类体内消炎和抗感染的蛋白是一样的。此研究报告的另一作者安德森表示，数千年以来，人类就已经培育出了黑色皮毛的家用狗。她说：“不过，如今，我们不仅看到野狗也有黑色皮毛，还发现黑色皮毛对狗非常有利。”基因测试表明，黑色皮毛的基因突变大约是在过去1-1.5万年间由狗传给狼的。虽然这是意外事件，但黑狼首次表明狼这种动物也经受了人类的基因改良。（生物谷Bioon.com）
生物谷推荐原始出处：
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.
