# 编者信息 熊荣川 明湖实验室 xiongrongchuan@126.com http://blog.sciencenet.cn/u/Bearjazz THE ICE AGES Studies of the last 20 years have produced great advances in our understanding of the palaeoclimate, and this continues apace from new data and theories regularly making headlines. Information is gathered from levels of oxygen and carbon isotopes, magnetic and CO, measures, animal, vegetable and mineral remains in cores from the seabed, land and ice, and this is providing evermore coherent descriptions and explanations. It is clear that the last 700000 years have been dominated by major ice ages with a roughly 100kyr cycle interrupted by relatively short warm interglacials such as we enjoy at present. The Milankovitch theory proposes that the pacemaker of this process is the orbital eccentricity of the earth around the sun (Hays, Imbrie Shackleton, 1976;Gribbin, 1989). This causes major changes in insolation and along with lesser variations in axial tilt (40000yr) and precession (23000yr) produces a complex of climatic oscillations. Going back further in the Pleistoceneand into the Pliocene several long records indicate that the ice ages were less intense prior to 700ky and that the ice sheets in the northern hemisphere began to grow large around 2.4Myr (Webb Bartlein, 1992). Thus while the orbital cycles go back beyond 3Myr, other factors such as tectonic movement and ocean currents must be modifymg their effects over longer periods. Furthermore, while the ice ages have become an increasingly dramatic feature of the Pleistocene, large oscillations in climate producing large changes in flora and fauna can be clearly traced back into the Tertiary. 冰河时代 过去 20 年的研究在我们对古气候的理解上取得了巨大的进展，经常上头条的新数据和新理论不断让我们深化了该领域的认识。信息是从海底、陆地和冰的氧碳同位素、磁性、一氧化碳和地质测量，以及动物、植物和矿物残留物等得来，这提供了更加连贯的描述和解释。很明显，过去 70 万年中主要是冰期占主导地位，中间被大约 10 万年温暖的间冰期隔开，如当前我们乐在其中这段时期。米兰科维奇理论认为，这个过程的起搏器是地球围绕太阳的轨道偏心率（ Hays, Imbrie Shackleton, 1976;Gribbin, 1989 ）。这主要导致了日晒的变化，伴随轴倾（ 40000 年）和旋进（ 23000 年）的较小变化，从而产生了复杂的气候波动。回到过去在更新世和上新世，一些长期的记录表明， 70 万年之前，冰期就不那么强烈，北半球的冰盖是在 240 万年前左右开始变大的（ Webb Bartlein, 1992 ）。因此，当轨道周期超过 300 万年时，其他因素，如构造运动和洋流必定在较长时间内调整其影响。此外，虽然冰期已成为更新世一个日益引人注目的特征，但导致动植物的大变化的气候大振荡，可以清楚地追溯到第三纪。 Hewitt G M . Some genetic consequences of ice ages, and their role in divergence and speciation . Biological Journal of the Linnean Society, 2010, 58(3):247-276.
# 编者信息 熊荣川 明湖实验室 xiongrongchuan@126.com http://blog.sciencenet.cn/u/Bearjazz There are perhaps two ways of approaching the effects of Pleistocene ice ages on the genetics of speciation, and like deduction and induction they are complementary. Firstly, we may ask what can palaeoenvironmental sciences tell us about these climate changes? How was the distribution of fauna and flora affected by them in the Tropical and Temperate regions? How would these changes operate in regions with different topographies, where mountains, plains, lakes and seas are variously distributed? What would all this do to the genetic processes and structure of the species? Secondly, from the other end, we ask what is the genetic structure of populations, races, species and species complexes, both locally and geographically? How diverged are sister species, subspecies and races, and can we date these? How much hybridization and introgression is there between sister taxa, and what are its consequences? What is the power of gene flow among populations? Is there equilibrium locally or broadly? What can recent invasions tell us about the genetic consequences of range changes? What can we learn from the field and laboratory experiments about the rate and limits of adaptation to changed environments? Having gathered such information, the next step is to join the two sets. Are there common points? Do certain historical events predict observed patterns? Can past processes be inferred from current genetic distribution? And then where do we need more data? 研究更新世冰期对物种形成遗传学的影响，可能有两种互补的方式，一种是演绎法，另一种是归纳法。首先，我们可能会问，古环境科学能告诉我们关于这些气候变化的什么？热带和温带地区动植物的分布如何受其影响？在山区、平原、湖泊和海洋分布不同的地区，这些变化将如何运作？所有这些对物种的遗传过程和结构有什么影响？第二，从另一个角度，我们问在区位和地貌尺度上，种群、种族、物种和物种复合体的遗传结构是什么？姐妹物种、亚种和种族有多大的差异，我们能确定这些分化的日期吗？姐妹分类群之间有多少杂交和渗入，其后果是什么？种群间基因流动的动力是什么？存在局部平衡或广域平衡吗？最近的入侵能告诉我们分布区域变化的遗传后果吗？关于适应环境变化的速率和极限，我们可以从实地和实验室实验中学到什么？在收集了这些信息之后，下一步就是整合这两者。有共同点吗？某些历史事件预测观察到的模式吗？过去的过程能从当前的遗传分布中推断出来吗？那么我们在哪里需要更多的数据呢？ Hewitt G M . Some genetic consequences of ice ages, and their role in divergence and speciation . Biological Journal of the Linnean Society, 2010, 58(3):247-276.
标签: 更新世
