華盛頓湖1957年和2006年出產(chǎn)的不同年份的棘魚的比較
生物谷報(bào)道：5月20日出版的《當(dāng)代生物學(xué)》刊登了一篇棘魚退化的研究報(bào)告,。美國西雅圖附近華盛頓湖的污染隨著時(shí)間漸漸消退時(shí),，一種名為棘魚的多刺小魚可能出現(xiàn)了倒退進(jìn)化，重新長出遠(yuǎn)古“裝甲”,。
20世紀(jì)50年代,，美國華盛頓州太平洋海岸的內(nèi)陸湖――華盛頓湖遭受嚴(yán)重的磷污染，大約10年后成了一個(gè)121400公頃的污水池,。之后,，美國花1.4億美元高價(jià)來清理此湖，使其變成了如今的游樂天堂,。然而這一恢復(fù)讓此湖中的棘魚出現(xiàn)了退化,，科學(xué)家分析其原因是湖中的捕食者如鮭魚的威脅促使此魚重新進(jìn)化成了舊時(shí)的模樣，長出了防御用的裝甲板,。
當(dāng)華盛頓湖遭受嚴(yán)重的磷污染時(shí),，能見度大約只有76厘米，棘魚根本不需裝甲來保護(hù),，因?yàn)槎阍谖勰嘀芯湍芴舆^捕食者的視線,。1968年,，此湖清理完畢之后，能見度達(dá)到了3米,，如今的能見度則有7.6米。
科學(xué)家發(fā)現(xiàn),，在清理之前,，只有6%的棘魚有完整的裝甲,，如今有49%的棘魚全身披滿裝甲了,，用骨質(zhì)板從頭到尾保護(hù)自己。另有35%的棘魚有部分裝甲,，其一半的身體被保護(hù)著,。該研究小組表示，這一戲劇性的快速適應(yīng)是一種倒退進(jìn)化的事例,，因?yàn)榧~本來是越來越進(jìn)化成沒有裝甲的,。（生物谷www.bioon.com）
生物谷推薦原始出處：
Current Biology，Vol 18, 769-774,，Jun Kitano，Catherine L. Peichel
Reverse Evolution of Armor Plates in the Threespine Stickleback
Jun Kitano,1 Daniel I. Bolnick,2 David A. Beauchamp,3 Michael M. Mazur,3 Seiichi Mori,4 Takanori Nakano,5 and Catherine L. Peichel1,
1 Division of Human Biology, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109
2 Section of Integrative Biology, University of Texas, Austin, Texas 78712
3 U.S. Geological Survey, Washington Cooperative Fish & Wildlife Research Unit, School of Aquatic and Fisheries Sciences, University of Washington, Seattle, Washington 98105
4 Biological Laboratory, Gifu-keizai University, Ogaki, Gifu 503-8550, Japan
5 Research Department, Research Institute for Humanity and Nature, 335 Takashima-cho, Kamigyo-ku, Kyoto 602-0878, Japan
Corresponding author
Catherine L. Peichel
[email protected]
Faced with sudden environmental changes, animals must either adapt to novel environments or go extinct. Thus, study of the mechanisms underlying rapid adaptation is crucial not only for the understanding of natural evolutionary processes but also for the understanding of human-induced evolutionary change, which is an increasingly important problem [1, 2, 3, 4, 5, 6, 7, 8]. In the present study, we demonstrate that the frequency of completely plated threespine stickleback fish (Gasterosteus aculeatus) has increased in an urban freshwater lake (Lake Washington, Seattle, Washington) within the last 40 years. This is a dramatic example of “reverse evolution,” [9] because the general evolutionary trajectory is toward armor-plate reduction in freshwater sticklebacks [10]. On the basis of our genetic studies and simulations, we propose that the most likely cause of reverse evolution is increased selection for the completely plated morph, which we suggest could result from higher levels of trout predation after a sudden increase in water transparency during the early 1970s. Rapid evolution was facilitated by the existence of standing allelic variation in Ectodysplasin (Eda), the gene that underlies the major plate-morph locus [11]. The Lake Washington stickleback thus provides a novel example of reverse evolution, which is probably caused by a change in allele frequency at the major plate locus in response to a changing predation regime.
