古代蝗虫飞越大西洋从非洲游历至美洲
  Ancient Swarm Brought Locusts To The New World

摘要：
    一个国际科研小组的研究人员日前表示，在300万年至500万年之前的某个时候，为数众多的一大群蝗虫从非洲西海岸起飞，在经历了一次不同寻常的跨越大西洋的航程之后，到达了新的世界——美洲大陆。
    Somewhere between three and five million years ago, a massive swarm of locusts took off from the west coast of Africa and made an unlikely voyage across the Atlantic Ocean to colonize the New World, says an international team of researchers.

    一个国际科研小组的研究人员日前表示，在300万年至500万年之前的某个时候，为数众多的一大群蝗虫从非洲西海岸起飞，在经历了一次不同寻常的跨越大西洋的航程之后，到达了新的世界——美洲大陆。

    据“每日科学”网站12月27日报道，来自加拿大多伦多大学、美国亚利桑那大学、马里兰大学、康纳尔大学以及美国农业部的科学家是在对20多种蝗虫的基因进行分析后，得出上述结论的。他们的这一研究成果还揭开了一个长久以来悬而未决的谜题，即为何非洲沙漠蝗（Schistocerca gregaria）关系最近的亲戚是在美洲大陆而不是在非洲大陆被发现的。

    报道说，沙漠蝗是世界上从经济学角度来说最为重要的昆虫之一。它们能聚集成巨大的蝗虫群，在很短的时间里对农作物造成毁灭性的打击。

    研究人员表示，这些蝗虫的DNA证据显示，非洲沙漠蝗的祖先们曾飞越了大西洋，并在美洲大陆生成了一个新的蝗虫种群。但是，科学家们目前尚不明确这些蝗虫是如何完成这次飞行的，因为这种昆虫的身体中并没有足够的脂肪以支持它们完成长达数天的行程。

    对此，多伦多大学的一位助理教授内森·拉夫卓伊表示：“一个不太可能的假设是，这些蝗虫在飞越大西洋的过程中，它们中很多都死亡了，并掉入水中。众多蝗虫的尸体形成了在水上漂浮的垫子。而其它的蝗虫则能享受前者为它们带来的便利，在这些垫子上休息并以前者的尸体为食。休息好之后，它们又再次起飞继续飞行。”而另外一种可能性则是，在为数众多的数百万只蝗虫当中，存在着少数一些例外的成员，它们以某种方式，在长距离飞行中保全了生命。

    影响蝗虫飞行的因素应该有很多。拉夫卓伊指出，当时的高空气流对蝗虫群的飞行就至关重要。近年来，也有这方面的例子——在1998年10月份，一群沙漠蝗也曾飞越大西洋，从非洲到达了加勒比地区。

    拉夫卓伊和同事在研究过程中利用从蝗虫有力的后腿上取下的肌肉样本，使用线粒体DNA序列重塑了沙漠蝗的进化史。

    报道说，这一研究是由美国《国家地理》和美国国家科学基金会资助的。研究成果被发表在最新一期的《伦敦皇家学会学报》杂志上。

环球雅思-中国第一雅思品牌 名师阵容 国内最大的连锁外语培训机构，被评为全国十大知名学校，连续多年荣膺中国最具影响力培训集团称号... 北京新航道学校-胡敏“中国雅思之父” 多所世界名校，可根据意愿选择留学国家与学校、国内两年、国外两年，节省大量费用与一年学习时间 北京雅思学校-刘洪波、张皓亲自授课 北雅 IELTS 培训基地是全国最早、最权威进行 IELTS 考试培训研究的专业化、正规化机构，强大的师资。 上海朗阁雅思学校-南方雅思培训首选 国内最大的雅思培训基地。拥有上百位全职中外雅思专家，25人小班授课、中外专家联合执教、保分承诺

韩企、日企定向培养 北京理工大学校本部招生   中国人民大学计划外 北京文理研修学院招生

    Somewhere between three and five million years ago, a massive swarm of locusts took off from the west coast of Africa and made an unlikely voyage across the Atlantic Ocean to colonize the New World, says an international team of researchers.

    Using genetic evidence from more than 20 species of locusts, scientists from the Universities of Toronto, Arizona, Maryland, Cornell University and the U.S. Department of Agriculture have answered a long-standing conundrum: why are the closest relatives of the African desert locust (Schistocerca gregaria) found in the New World, rather than Africa?

    The desert locust is one of the world's most economically important insects, and is capable of forming massive swarms that devastate crops.

    DNA shows that ancestors of the desert locust flew across the Atlantic and gave rise to a diverse group of New World species. "If we were standing on the coast of Africa, we might have these swarms of locusts heading off across the Atlantic," says Nathan Lovejoy, an assistant professor of in the Department of Life Sciences at the University of Toronto at Scarborough, who led the research along with Sean Mullen, now a postdoctoral researcher at the University of Maryland.

    How the locusts made the trans-Atlantic flight is unclear, since the insects don't have enough fat to power a trip lasting several days. "One unlikely hypothesis is that while the locusts were flying across, as their brethren died and landed in the ocean, they formed huge floating mats of dead locusts," says Lovejoy. "The other locusts would land on these mats, rest and feed on the dead bodies, then take off and keep flying."

    Another possibility is that among the millions of swarming locusts were a few exceptional insects that somehow managed to survive the flight. Lovejoy adds that high-altitude winds would have been essential for the swarm's flight. There is a modern-day example of this phenomenon -- in October 1998, a swarm of desert locusts crossed the Atlantic, travelling from Africa to the Caribbean.

    Using muscle samples taken from the powerful hind legs of locusts, Lovejoy and his colleagues used mitochondrial DNA sequences to reconstruct the evolutionary history of the Schistocerca locusts. The team found that the desert locust lineage gave rise to the more than 50 Schistocerca species found in the western hemisphere.

    The study, which appears in the latest issue of the journal Proceedings of the Royal Society of London, was funded by National Geographic and the National Science Foundation.

    The University of Toronto is Canada's leading teaching and research university and aims to be among the world's best. For twelve consecutive years, U of T has taken the top spot among medical/doctoral universities in the annual Maclean's magazine university ranking. With more than 70,000 students, U of T comprises 28 divisions, colleges and faculties on three campuses. This includes 14 professional faculties, nine fully-affiliated teaching hospitals, numerous research centres and Canada's largest university library system -- the third largest in North America.