本帖最后由 细胞海洋 于 2014-8-4 09:26 编辑 / z2 L# V/ m( i9 p9 ]# \/ |
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2014年7月24日 Nature' b- Q; X2 P3 \" |; d 0 E9 D j" F% W; A
Antarctic fur seals (Arctocephalus gazella) on an iceberg at Bird Island, South Georgia. This species was hunted almost to extinction by the early twentieth century but numbers began to recover when sealing operations stopped, and thanks to an abundant food supply it has survived in large numbers. But fur seals are particularly [url=http://staging-www.nature.com/nature/journal/v511/n7510/full/511414a.html]vulnerable to climate change[/url] as they inhabit a region with fast-changing temperatures, and their relatively long generation time limits their ability to adapt evolutionarily. [url=http://staging-www.nature.com/nature/journal/v511/n7510/full/nature13542.html]An analysis of three decades of data from South Georgia[/url] now shows that the seals are in decline again, with female numbers down by some 30% between 2003 and 2012. Harsh conditions have, however, selected for higher genetic heterozygosity among females. While this is not in itself an evolutionary response, as environmental conditions continue to worsen, heterozygote advantage could help maintain genetic variation, potentially buying time to allow the species to respond via adaptation. Cover photo: Jaume Forcada 2 l+ [9 X( M$ k( O0 V7 k/ ]0 z- I
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