美国研究人员最近发现，从上个冰川时代残留下来的阿德利企鹅骨骼中提取的DNA样本将有助于揭示物种如何应对气候变化。
布里斯班市格里菲斯大学的进化生物学家David Lambert在新一期遗传学杂志《公共科学图书馆·遗传学》（PLoS Genetics）上发表了他们对于生活在3.7万前的企鹅DNA样本的分析成果。Lambert教授说，对于研究气候变化，企鹅是非常合适的物种。它们在生活环境中感受的温度变化要比赤道地区的那些动物剧烈的多。
自从上一次盛冰期以来，企鹅们已经经历了地球上多次出现的气候变暖。他估计在距今十二万年的上个冰期之前，企鹅们就已经存在了。
阿德利企鹅在相当长的时期中都保持了相当大的种群数量，这样的物种并不多见。一个物种通常可以通过地理上的迁徙让自己生活在最适宜的温度中，从而应对气候变化带来的影响。但是阿德利企鹅从没有迁移到别处，它们一直都呆在最冷的地方。
阿德利企鹅能在剧烈的温度变化中生存下来，说明有些物种能够在不迁徙的情况下应对气候变化带来的考验。Lambert和同事们对南极洲企鹅进化速率的研究或许可以揭开这个现象背后的秘密。
研究人员从在南极极端干燥和寒冷的环境中保存下来的三万七千年前的企鹅骨骼中提取了多份DNA样本。他们将现在在南极生活的企鹅妈妈和他们孩子的基因样本进行比对，并再和它们祖先的DNA进行比对。结果显示，三万七千年来企鹅代际变化速率一直保持稳定。
这一发现反击了当前生物学者对进化速率的一种认识，他们认为生物进化在短期会加快，而长期则相对较慢。更为重要的成果是，Lambert和他的团队发现验证了早期的研究成果，阿德利企鹅的进化速率比现在人们想象的要快。这也可能解释为什么这些企鹅能够在气候剧烈变化的环境中存活下来。进化速率和企鹅一样快的动物还有一种新西兰特有的爬行动物tuatoara、野牛、棕熊和穴居狮子等。
这些DNA分析将焦点放在基因变化而不是自然选择。所谓“中性”基因对于形成一个演变速率稳定的“生物原子时钟”至关重要。而自然选择造成的结果是生物演化在一些一段时间内极为迅速，而在其它时期则几乎稳定不动。阿德莱德大学的进化生物学家Jeremy Austin认为这项成果将促使人们质疑进化演变速率对时间的依赖性。但是要揭示进化速率快慢的话，三万七千年这个周期显然还不够长。生物学界讨论进化速率时，通常会讲到一百万年甚至更长周期内的变化。将企鹅和更古老物种的DNA序列进行对比可能更有说服力一些。
Lambert相信他的团队肯定会在南极大陆更深处的永久冻土层中发现百万年前的企鹅遗迹。（生物谷Bioon.com）
生物谷推荐原始出处：
PLoS Genetics，4(10): e1000209. doi:10.1371/journal.pgen.1000209，Craig D. Millar, David M. Lambert
Mutation and Evolutionary Rates in Adélie Penguins from the Antarctic
Craig D. Millar1, Andrew Dodd2, Jennifer Anderson2, Gillian C. Gibb2, Peter A. Ritchie2¤a, Carlo Baroni3,4, Michael D. Woodhams5, Michael D. Hendy5, David M. Lambert2¤b*
1 Allan Wilson Centre for Molecular Ecology and Evolution, School of Biological Sciences, University of Auckland, Auckland, New Zealand, 2 Allan Wilson Centre for Molecular Ecology and Evolution, Institute of Molecular BioSciences, Massey University, Auckland, New Zealand, 3Dipartmento Scienze della Terra, Università di Pisa, Pisa, Italy, 4 Consiglio Nazionale Ricerche, Centro Studio Geologia Strutturale, Pisa, Italy, 5 Allan Wilson Centre for Molecular Ecology and Evolution, Institute of Fundamental Sciences, Massey University Palmerston North, Palmerston North, New Zealand
Precise estimations of molecular rates are fundamental to our understanding of the processes of evolution. In principle, mutation and evolutionary rates for neutral regions of the same species are expected to be equal. However, a number of recent studies have shown that mutation rates estimated from pedigree material are much faster than evolutionary rates measured over longer time periods. To resolve this apparent contradiction, we have examined the hypervariable region (HVR I) of the mitochondrial genome using families of Adélie penguins (Pygoscelis adeliae) from the Antarctic. We sequenced 344 bps of the HVR I from penguins comprising 508 families with 915 chicks, together with both their parents. All of the 62 germline heteroplasmies that we detected in mothers were also detected in their offspring, consistent with maternal inheritance. These data give an estimated mutation rate (μ) of 0.55 mutations/site/Myrs (HPD 95% confidence interval of 0.29–0.88 mutations/site/Myrs) after accounting for the persistence of these heteroplasmies and the sensitivity of current detection methods. In comparison, the rate of evolution (k) of the same HVR I region, determined using DNA sequences from 162 known age sub-fossil bones spanning a 37,000-year period, was 0.86 substitutions/site/Myrs (HPD 95% confidence interval of 0.53 and 1.17). Importantly, the latter rate is not statistically different from our estimate of the mutation rate. These results are in contrast to the view that molecular rates are time dependent.
