保存在印度的年齡為5000萬年的琥珀中的昆蟲可能提供證據(jù)表明該地區(qū)的生物群并非像目前認(rèn)為的那樣孤立進(jìn)化,。印度的獨(dú)特的動(dòng)植物群被認(rèn)為在印度大陸1億年的向北運(yùn)動(dòng)中進(jìn)化了出來，這種向北運(yùn)動(dòng)以形成了喜馬拉雅山脈的大碰撞而終結(jié)。
Jes Rust及其同事從印度西部5000萬年前的沉積物中提取了超過300磅琥珀,，并發(fā)現(xiàn)了一種獨(dú)特的化學(xué)特征，它提示這種樹脂是由全球廣泛分布的一類熱帶樹產(chǎn)生的,。這組科學(xué)家用溶劑溶解了這種琥珀,，并獲取了完整保存的來自超過55科的古代昆蟲、蜘蛛綱動(dòng)物和甲殼綱動(dòng)物的700多種標(biāo)本以及豐富的植物和真菌殘骸,。這些昆蟲顯示出了與來自亞洲和澳大利亞的當(dāng)代物種以及最遠(yuǎn)見于墨西哥和中美洲的古代祖先的出人意料的地理聯(lián)系,。
這組作者說，該研究提供了直接的化石證據(jù),，證明了印度琥珀含有具有多樣的動(dòng)物群的熱帶森林的早期記錄,，并證明了碰撞前的印度可能并非像人們認(rèn)為的那樣在生物學(xué)上是孤立的。（生物谷Bioon.com）
生物谷推薦英文摘要：
PNAS doi: 10.1073/pnas.1007407107
Biogeographic and evolutionary implications of a diverse paleobiota in amber from the early Eocene of India
Jes Rusta,1, Hukam Singhb, Rajendra S. Ranac, Tom McCanna, Lacham Singhc, Ken Andersond, Nivedita Sarkare, Paul C. Nascimbenef, Frauke Stebnera, Jennifer C. Thomasg, Monica Solórzano Kraemera,h, Christopher J. Williamsi, Michael S. Engelg, Ashok Sahnie,j, and David Grimaldif,1
aSteinmann Institute, University of Bonn, 53115 Bonn, Germany;
bBirbal Sahni Institute of Palaeobotany, Lucknow 226007, India;
cDepartment of Geology; Hemwati Nandan Bahuguna Garhwal University, Srinagar 246174, India;
dDepartment of Earth Sciences, Southern Illinois University, Carbondale, IL 62901;
eCentre for Advanced Study in Geology, University of Lucknow, Lucknow 226007, India;
fAmerican Museum of Natural History, New York, NY 10024-5192;
gDivision of Entomology, Natural History Museum, and Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66049-2811;
hSenckenberg Research Institute and Museum, 60325 Frankfurt, Germany;
iDepartment of Earth and Environment, Franklin and Marshall College, Lancaster, PA 17603; and
jCentre of Advanced Study in Geology, Panjab University, Chandigarh 160022, India
For nearly 100 million years, the India subcontinent drifted from Gondwana until its collision with Asia some 50 Ma, during which time the landmass presumably evolved a highly endemic biota. Recent excavations of rich outcrops of 50–52-million-year-old amber with diverse inclusions from the Cambay Shale of Gujarat, western India address this issue. Cambay amber occurs in lignitic and muddy sediments concentrated by near-shore chenier systems; its chemistry and the anatomy of associated fossil wood indicates a definitive source of Dipterocarpaceae. The amber is very partially polymerized and readily dissolves in organic solvents, thus allowing extraction of whole insects whose cuticle retains microscopic fidelity. Fourteen orders and more than 55 families and 100 species of arthropod inclusions have been discovered thus far, which have affinities to taxa from the Eocene of northern Europe, to the Recent of Australasia, and the Miocene to Recent of tropical America. Thus, India just prior to or immediately following contact shows little biological insularity. A significant diversity of eusocial insects are fossilized, including corbiculate bees, rhinotermitid termites, and modern subfamilies of ants (Formicidae), groups that apparently radiated during the contemporaneous Early Eocene Climatic Optimum or just prior to it during the Paleocene-Eocene Thermal Maximum. Cambay amber preserves a uniquely diverse and early biota of a modern-type of broad-leaf tropical forest, revealing 50 Ma of stasis and change in biological communities of the dipterocarp primary forests that dominate southeastern Asia today.
