Parducci L, Suyama Y, Lascoux M, Bennett K D
Department of Earth Sciences, Palaeobiology Program, Uppsala University, Villavägen 16, SE-752 36 Uppsala, Sweden.
Mol Ecol. 2005 Aug;14(9):2873-82. doi: 10.1111/j.1365-294X.2005.02644.x.
Assessments of plant population dynamics in space and time have depended on dated records of fossil pollen synthesized on a subcontinental scale. Genetic analyses of extant populations have revealed spatial relationships that are indicative of past spatial dynamics, but lack an explicit timescale. Synthesis of these data requires genetic analyses from abundant dated fossil material, and this has hitherto been lacking. Fossil pollen is the most abundant material with which to fill this data gap. Here we report genetic analyses of fossil pollen retrieved from Holtjärnen postglacial lake sediment in Sweden and show that plastid DNA is recoverable from Scots Pine and Norway spruce pollen grains that are 100 and 10 000 years old. By sequencing clones from two short plastid PCR products and by using multiple controls we show that the ancient sequences were endogenous to the fossil grains. Comparison of ancient sequences and those obtained from an extant population of Scots pine establishes the first genetic link between extant and fossil samples in this species, providing genetic continuity through time. The finding of one common haplotype present in modern, 100-year old and 10 000-year old samples suggests that it may have persisted near Holtjärnen throughout the postglacial period. This retrieval of ancient DNA from pollen has major implications for plant palaeoecology in conifer species by allowing direct estimates of population dynamics in space and time.
对植物种群在空间和时间上动态变化的评估一直依赖于在次大陆尺度上综合的已标注日期的化石花粉记录。对现存种群的遗传分析揭示了一些空间关系，这些关系暗示了过去的空间动态，但缺乏明确的时间尺度。综合这些数据需要对大量已标注日期的化石材料进行遗传分析，而目前一直缺乏此类分析。化石花粉是填补这一数据空白的最丰富材料。在此，我们报告了从瑞典霍尔特耶尔嫩冰后期湖泊沉积物中提取的化石花粉的遗传分析结果，并表明可从树龄分别为100年和10000年的欧洲赤松和挪威云杉花粉粒中提取质体DNA。通过对两个短质体PCR产物的克隆进行测序并使用多个对照，我们表明这些古老序列是化石花粉粒内源性的。将古老序列与从现存欧洲赤松种群中获得的序列进行比较，建立了该物种现存样本与化石样本之间的首个遗传联系，提供了贯穿时间的遗传连续性。在现代、100年树龄和10000年树龄样本中均存在一种常见单倍型，这一发现表明它可能在整个冰后期都在霍尔特耶尔嫩附近存在。从花粉中提取古老DNA对针叶树种的植物古生态学具有重大意义，因为它可以直接估计种群在空间和时间上的动态变化。
