資料來源: Barry Roal Carlsen, University of Wisconsin-Madison
據(jù)11月20日的《科學(xué)》雜志報道說,，有關(guān)如猛犸象,、乳齒象以及地懶等大型動物是如何滅絕的，以及它們的消失是如何影響北美的生態(tài)系統(tǒng)等問題終于在其糞便中得到了解答,。 在一項闡明那些大約在1萬3000年前在最后的冰川期結(jié)束時滅絕的動物的研究中,，Jacquelyn Gill及其同僚分析了從印地安納州Appleman Lake的遠(yuǎn)古沉積層中獲取的花粉、木炭以及Sporormiella (小莢孢腔菌) [這是一種生長在大型食草動物糞便中的特殊真菌],。 由于Sporormiella 的量為人們提供了有關(guān)當(dāng)時大型食草動物所產(chǎn)生的生物質(zhì)的一種指標(biāo),，因此研究人員能夠?qū)⒋藬?shù)據(jù)與有關(guān)植被及來自花粉和木炭的火燒情況進(jìn)行相關(guān)聯(lián)系。
研究發(fā)現(xiàn),，這些巨型動物（稱作巨型動物群）的種群數(shù)在Clovis人的出現(xiàn),、大規(guī)模植物群落變化以及火燒增加的1000多年之前就已開始下降。 因此,，盡管研究人員過去認(rèn)為,，Clovis狩獵者及其/或這些環(huán)境的變遷導(dǎo)致了北美巨型動物群的衰減；但現(xiàn)在看來,，所發(fā)生的情況完全倒轉(zhuǎn)了過來：發(fā)生在1萬4800年至1萬3700年之前的巨型動物群的緩慢的滅絕發(fā)生在Clovis人出現(xiàn)之前,；而且它是植被改變和火燒增加的一個原因而非其結(jié)果。 這一發(fā)現(xiàn)還排除了人們提出的發(fā)生在1萬2900年前的來自地球外的撞擊事件的可能性。 一篇由Christopher Johnson所撰寫的Perspective對這一新的時間軸進(jìn)行了更為詳盡的解釋,。（生物谷Bioon.com）
生物谷推薦原始出處：
Science 20 November 2009:DOI: 10.1126/science.1179504
Pleistocene Megafaunal Collapse, Novel Plant Communities, and Enhanced Fire Regimes in North America
Jacquelyn L. Gill,1,2 John W. Williams,1,2 Stephen T. Jackson,3 Katherine B. Lininger,1 Guy S. Robinson4
Although the North American megafaunal extinctions and the formation of novel plant communities are well-known features of the last deglaciation, the causal relationships between these phenomena are unclear. Using the dung fungus Sporormiella and other paleoecological proxies from Appleman Lake, Indiana, and several New York sites, we established that the megafaunal decline closely preceded enhanced fire regimes and the development of plant communities that have no modern analogs. The loss of keystone megaherbivores may thus have altered ecosystem structure and function by the release of palatable hardwoods from herbivory pressure and by fuel accumulation. Megafaunal populations collapsed from 14,800 to 13,700 years ago, well before the final extinctions and during the B?lling-Aller?d warm period. Human impacts remain plausible, but the decline predates Younger Dryas cooling and the extraterrestrial impact event proposed to have occurred 12,900 years ago.
1 Department of Geography, University of Wisconsin, Madison, WI 53706, USA.
2 Center for Climatic Research, University of Wisconsin, Madison, WI 53706, USA.
3 Department of Botany, University of Wyoming, Laramie, WY 82071, USA.
4 Department of Natural Science, Lincoln Center Campus, Fordham University, New York, NY 10023, USA.
