據(jù)美國(guó)科學(xué)促進(jìn)會(huì)網(wǎng)站報(bào)道,，科研人員通過(guò)DNA（脫氧核糖核酸）測(cè)序，發(fā)現(xiàn)北極熊和棕熊在過(guò)去的10萬(wàn)年中曾經(jīng)多次成功交配,，如今的北極熊也擁有愛(ài)爾蘭棕熊“血統(tǒng)”,。這一研究對(duì)提請(qǐng)有關(guān)部門加強(qiáng)對(duì)北極熊與棕熊雜交后代的保護(hù)以維持該物種的延續(xù)有重大意義。研究成果發(fā)表在近日出版的《當(dāng)代生物學(xué)》雜志上,。
研究人員利用線粒體DNA測(cè)序來(lái)追蹤北極熊的進(jìn)化史,。通過(guò)從世界各地收集的化石中提取線粒體基因組并對(duì)其進(jìn)行測(cè)序，研究人員可以了解北極熊的母系是如何在時(shí)空變換中一代代延續(xù)下來(lái)的,。之后他們對(duì)線粒體類型與環(huán)境和北極熊棲息地的變換進(jìn)行關(guān)聯(lián)研究。
研究表明,，現(xiàn)在北極熊的母系是它們的祖先與一群目前已經(jīng)滅絕的棕熊雜交的后代,。這些棕熊生活在現(xiàn)在的英國(guó)和愛(ài)爾蘭附近，而不是之前所知的阿拉斯加海岸,。這次雜交很有可能就發(fā)生在最后一次冰河時(shí)期或者之前的一段時(shí)間,。
科研人員認(rèn)為，這項(xiàng)北極熊進(jìn)化史的新發(fā)現(xiàn)會(huì)為未來(lái)的北極熊保護(hù)戰(zhàn)略提供很大幫助,，提醒人們對(duì)北極熊與棕熊的雜交后代的保護(hù)未雨綢繆,。
北極熊生活在地球最極端的環(huán)境中,，但是不斷升高的氣溫和海冰的融化重塑了北極大陸，威脅到了北極熊的生存,。
“氣候變化迫使北極熊和棕熊進(jìn)入彼此的棲息地,，當(dāng)它們之間有所交流后就可以毫無(wú)障礙地進(jìn)行交配了。”賓夕法尼亞州立大學(xué)的貝絲·夏皮羅說(shuō),，“10萬(wàn)多年以來(lái),，北極熊和棕熊在某些機(jī)遇下進(jìn)行雜交。氣候變化的壓力影響了北極熊的進(jìn)化和未來(lái)的發(fā)展,。”
目前人類對(duì)這兩類熊的保護(hù)比較薄弱,，尤其對(duì)它們雜交后代的保護(hù)意識(shí)還不強(qiáng)。“鑒于受威脅的北極地區(qū)的雜交后代數(shù)目不斷增加,，有必要重新衡量一下對(duì)北極熊雜交后代的保護(hù),，因?yàn)樗鼈兛赡茉谖锓N生存中發(fā)揮著重要作用。”夏皮羅說(shuō),。(生物谷 Bioon.com)
生物谷推薦原文出處：
Current Biology doi:10.1016/j.cub.2011.05.058
Ancient Hybridization and an Irish Origin for the Modern Polar Bear Matriline
Ceiridwen J. Edwards1, Marc A. Suchard, Philippe Lemey, John J. Welch, Ian Barnes, Tara L. Fulton, Ross Barnett, Tamsin C. O'Connell, Peter Coxon, Nigel Monaghan, Cristina E. Valdiosera, Eline D. Lorenzen, Eske Willerslev, Gennady F. Baryshnikov, Andrew Rambaut, Mark G. Thomas, Daniel G. Bradley and Beth Shapiro
Background Polar bears (Ursus maritimus) are among those species most susceptible to the rapidly changing arctic climate, and their survival is of global concern. Despite this, little is known about polar bear species history. Future conservation strategies would significantly benefit from an understanding of basic evolutionary information, such as the timing and conditions of their initial divergence from brown bears (U. arctos) or their response to previous environmental change. Results We used a spatially explicit phylogeographic model to estimate the dynamics of 242 brown bear and polar bear matrilines sampled throughout the last 120,000 years and across their present and past geographic ranges. Our results show that the present distribution of these matrilines was shaped by a combination of regional stability and rapid, long-distance dispersal from ice-age refugia. In addition, hybridization between polar bears and brown bears may have occurred multiple times throughout the Late Pleistocene.
