2009年1月7日 星期三

那隻新的粉紅鬣蜥

以下是摘錄自yahoo來自中央社譯路透社的新聞文字:

南美厄瓜多加拉巴戈斯群島 發現新物種粉紅色鬣蜥 (路透倫敦6日電)

英國生物學家達爾文(Charles Darwin)造訪加拉巴戈斯群島(Galapagos Islands)並觀察島上雀類後,提出物種多樣性的理論。不過,他未發現的粉紅色鬣蜥,可能證實物種分化出現得更早。
研究主持人、羅馬第二大學(University Tor Vergata)的詹蒂列(Gabriele Gentile)說,這項發現首度指出,這種帶有黑色斑紋的爬蟲類是一種全新物種。人類在1986年首度發現粉紅色鬣蜥,之後僅數度再發現其蹤跡。這項研究並使人類更深入地了解偏遠島嶼物種的進化過程。這些物種與數百萬年前相差無幾,且是達爾文天擇進化論的靈感來源。其中許多物種只存在於加拉巴戈斯群島。達爾文1835年造訪加拉巴戈斯群島時觀察到,分布在約100個島嶼上的雀類具有各種不同形狀的喙部。這項觀察是形成其進化理論的關鍵要點。(中央社)翻譯

以下是路透的原文 [網址]

Pink iguanas unseen by Darwin offer evolution clue Tue Jan 6, 2009 8:58am EST

By Michael Kahn

LONDON (Reuters) - Pink iguanas unknown to Charles Darwin during his visits to the Galapagos islands may provide evidence of species divergence far earlier than the English naturalist's famous finches, researchers said Monday. The findings also for the first time describe the black-striped reptiles -- first seen in 1986 and only a few more times since -- as a new species, said Gabriele Gentile of the University Tor Vergata in Rome, who led the study. They also add to understanding of the evolution of species on the remote islands, which remain much as they were millions of years ago and which inspired Darwin's theory of evolution by natural selection. Many of its species are found nowhere else. "Despite the attention given to them, the Galapagos have not yet finished offering evolutionary novelties," Gentile and colleagues wrote in the Proceedings of the National Academy of Sciences. "So far, this species is the only evidence of ancient diversification along the Galapagos land iguana lineage and documents one of the oldest events of divergence ever recorded in the Galapagos." During Darwin's visit to the Galapagos in 1835 his observations of finch varieties with different-shaped beaks scattered across the archipelago's some 100 islands were a key element in his formulation of the principles of evolution. His studies on how one type had evolved into several after a probable chance migration thousands of years earlier from the Latin American mainland lay at the heart of his major work "On the Origin of Species," published in 1859. As the finches spread around the islands and their populations became cut off from each other, the birds adapted to the food locally available by developing beaks of a shape most suitable to harvest it, his research showed. Darwin did not visit areas inhabited by the pink land iguana and so missed the species, whose existence suggests diversification in the Galapagos happened some five million years ago. That is far earlier than attributed to most other Galapagos species like the finches, Gentile said. "We were not the first to see this form but we were the first to say what it is and that it is a new species," Gentile said in a telephone interview. A genetic analysis showed that the pink reptile likely originated in the Galapagos and split from other iguana populations some five million years ago when the archipelago was still forming, the researchers said. The creatures only seem to live near a single volcano at most 350,000 years old, which means the reptiles that grow longer than a meter and up to 12 kilograms must have at one time existed elsewhere in the Galapagos, Gentile said. The researchers documented fewer than 40 of the iguanas over two years and Gentile said conservation efforts and funds are urgently needed to keep the species from dying off. "We think the population is very small and there is a great risk of extinction," Gentile said.

(Reporting by Michael Kahn; editing by Jon Boyle)

以下是義大利研究團發表於PNAS的原文連結:

An overlooked pink species of land iguana in the Galápagos

Abstract

Despite the attention given to them, the Galápagos have not yet finished offering evolutionary novelties. When Darwin visited the Galápagos, he observed both marine (Amblyrhynchus) and land (Conolophus) iguanas but did not encounter a rare pink black-striped land iguana (herein referred to as “rosada,” meaning “pink” in Spanish), which, surprisingly, remained unseen until 1986. Here, we show that substantial genetic isolation exists between the rosada and syntopic yellow forms and that the rosada is basal to extant taxonomically recognized Galápagos land iguanas. The rosada, whose present distribution is a conundrum, is a relict lineage whose origin dates back to a period when at least some of the present-day islands had not yet formed. So far, this species is the only evidence of ancient diversification along the Galápagos land iguana lineage and documents one of the oldest events of divergence ever recorded in the Galápagos. Conservation efforts are needed to prevent this form, identified by us as a good species, from extinction.