生物谷報道：來自美國弗吉尼亞理工大學(xué)（Virginia Polytechnic Institute and State University,，生物谷注）的研究人員在生物進化研究方面取得了突破性的研究進展：他們發(fā)現(xiàn)地球上復(fù)雜的生命體經(jīng)過了兩次,，而不是一次“爆炸”而迅速繁衍。這一研究成果公布在Science雜志上,。
文章的通訊作者是來自弗吉尼亞理工大學(xué)的古生物學(xué)家肖樹華博士（Shuhai Xiao,，音譯，生物谷注），其早年畢業(yè)于北京大學(xué),，后于哈佛大學(xué)獲得博士學(xué)位,，現(xiàn)任弗吉尼亞理工大學(xué)地球科學(xué)系副教授。
地球上最大一次物種分裂發(fā)生于5億4200萬年前,，被稱作寒武紀生命大爆炸,。但是在這篇文章中，研究人員認為,，一個和它相似的,，迅速的進化爆炸在其爆炸的3300萬年前發(fā)生，他們將這次事件成為阿瓦隆爆炸,。肖博士表示：“現(xiàn)在看來從575年至5億2000萬年前肉眼可見的生命體,，經(jīng)歷不止一次，而至少是兩次巨大的突發(fā)形態(tài)擴張,。”
研究人員分析研究了6億3500年到5億4200年前的震旦紀期間的生命體,，并比較了200種不同的物種以揭示他們的體型--以及豐富的多樣性--在同期出現(xiàn)。他們發(fā)現(xiàn),，盡管在生物多樣性上有了首次推進,，但是震旦紀的所有生物都在隨之而來的寒武紀爆炸前全部消失。“阿瓦隆爆炸代表了一個獨立的,，和寒武紀爆炸相似的進化模式失敗的試驗,。”
生物谷推薦原始出處：
Science 4 January 2008:
Vol. 319. no. 5859, pp. 81 - 84
DOI: 10.1126/science.1150279
The Avalon Explosion: Evolution of Ediacara Morphospace
Bing Shen, Lin Dong, Shuhai Xiao,* Micha Kowalewski
Ediacara fossils [575 to 542 million years ago (Ma)] represent Earth's oldest known complex macroscopic life forms, but their morphological history is poorly understood. A comprehensive quantitative analysis of these fossils indicates that the oldest Ediacara assemblage—the Avalon assemblage (575 to 565 Ma)—already encompassed the full range of Ediacara morphospace. A comparable morphospace range was occupied by the subsequent White Sea (560 to 550 Ma) and Nama (550 to 542 Ma) assemblages, although it was populated differently. In contrast, taxonomic richness increased in the White Sea assemblage and declined in the Nama assemblage. These diversity changes, occurring while morphospace range remained relatively constant, led to inverse shifts in morphological variance. The Avalon morphospace expansion mirrors the Cambrian explosion, and both events may reflect similar underlying mechanisms.
Department of Geosciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA.
* To whom correspondence should be addressed. E-mail: [email protected]
附：
Shuhai Xiao
Associate Professor of Geobiology
Department of Geosciences, Virginia Tech
Blacksburg, VA 24061, USA
Biography:
Associate Professor: Virginia Tech, 2005-;
Assistant Professor: Virginia Tech, 2003-2005;
Assistant Professor: Tulane University, 2000-2003;
Postdoctoral Fellow: Harvard University, 1998-2000;
Research Assistant: Nanjing Institute of Geology and Paleontology, 1991-1993;
PhD: Harvard University, 1998;
AM: Harvard University, 1996;
MSc: Beijing University, 1991;
BSc: Beijing University, 1988;
Research:
Focuses: Precambrian Geobiology; Early Animal History; Proterozoic Algal Fossils; Lagerst䴴en; Taphonomy;
Other Interests: Carbonates; Isotopes; Fossil Record of Microbes;
The Doushantuo project
In the past several years, Xiao and his colleagues have been focusing on the Neoproterozoic Doushantuo Formation (ca. 550-630 million years old) in South China. The Doushantuo Formation contains multiple taphonomic windows. Extraordinary fossils such as animal embryos and multicellular algae are preserved in Doushantuo phosphorites and cherts. Macroscopic algal fossils occur in Doushantuo shales. Together these taphonomic windows give a clearer and more complete picture of the Neoproterozoic biosphere and provides insights into preservational biases of the Neoproterozoic fossil record. Reliable reconstruction of the temporal and spatial distribution of Neoproterozoic biodiversity is critical to the understanding of the interactions between Neoproterozoic climate change and biological evolution.
