美日两国科学家近日在棘鱼（stickleback fish）身上的实验首次显示，新的性染色体的进化驱动了脊椎动物新种的形成。相关研究成果9月27日在线发表于《自然》杂志。

直至目前，多数证据显示新物种的产生是因适应环境而致。但日本东北大学进化生物学家Jun Kitano领导研究小组发现，日本海棘鱼拥有着与其祖先不同的性染色体，其祖先的Y染色体与一个常染色体融合，创造出了一个新的性染色体。

研究小组还观察到，雄性日本海棘鱼比其祖先表现出更多的攻击性交配行为，使得进化自祖先群体的雌性避免与它们交配。而且在实验室测试中，这两种群体交配产生的后代是不育的。

研究小组发现，造成雄性日本海棘鱼攻击性交配行为的基因位于这一新的Y染色体上。这种交配行为阻止了两种群体进行交配，使得日本海棘鱼成为了一个新种。

瑞士联邦水生科技研究所鱼类生态学家和进化学家Ole Seehausen表示，这一研究是“非凡的”，“这是首次研究显示，脊椎动物性染色体进化与新种进化之间存在直接联系”。

不过该研究并没有回答，两性间的冲突是否驱动了新性染色体的进化。

Nature 27 September 2009 | doi:10.1038/nature08441

A role for a neo-sex chromosome in stickleback speciation

Jun Kitano1,7, Joseph A. Ross1,2,7, Seiichi Mori3, Manabu Kume4, Felicity C. Jones5, Yingguang F. Chan5, Devin M. Absher6,7, Jane Grimwood6,7, Jeremy Schmutz6,7, Richard M. Myers6,7, David M. Kingsley5 & Catherine L. Peichel1

1 Division of Human Biology, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, Washington 98109, USA
2 Graduate Program in Molecular and Cellular Biology, University of Washington, Seattle, Washington 98195, USA
3 Biological Laboratory, Gifu-keizai University, Ogaki, Gifu 503-8550, Japan
4 Aqua Restoration Research Center, Public Works Research Institute, Kakamigahara, Gifu 501-6021, Japan
5 Department of Developmental Biology and Howard Hughes Medical Institute, Stanford University, Stanford, California 94305, USA
6 Department of Genetics and Stanford Human Genome Center, Stanford University, Stanford, California 94304, USA
7 Present addresses: Department of Ecology and Evolutionary Biology, Graduate School of Life Sciences, Tohoku University, Sendai, Miyagi 980-8578, Japan (J.K.); Department of Biology, University of Maryland, College Park, Maryland 20742, USA (J.A.R.); HudsonAlpha Institute for Biotechnology, Huntsville, Alabama 35806, USA (D.M.A., J.G., J.S. and R.M.M.)
Correspondence to: Catherine L. Peichel1 Correspondence and requests for materials should be addressed to C.L.P.

Sexual antagonism, or conflict between the sexes, has been proposed as a driving force in both sex-chromosome turnover and speciation. Although closely related species often have different sex-chromosome systems, it is unknown whether sex-chromosome turnover contributes to the evolution of reproductive isolation between species. Here we show that a newly evolved sex chromosome contains genes that contribute to speciation in threespine stickleback fish (Gasterosteus aculeatus). We first identified a neo-sex chromosome system found only in one member of a sympatric species pair in Japan. We then performed genetic linkage mapping of male-specific traits important for reproductive isolation between the Japanese species pair. The neo-X chromosome contains loci for male courtship display traits that contribute to behavioural isolation, whereas the ancestral X chromosome contains loci for both behavioural isolation and hybrid male sterility. Our work not only provides strong evidence for a large X-effect on reproductive isolation in a vertebrate system, but also provides direct evidence that a young neo-X chromosome contributes to reproductive isolation between closely related species. Our data indicate that sex-chromosome turnover might have a greater role in speciation than was previously appreciated.