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BACKGROUND/AIMS: Recently, new palaeoecological records supported by molecular analyses and palaeodistributional modelling have provided more comprehensive insights into plant behaviour during the last Quaternary cycle. We reviewed the migration history of species of subgenus Alnus during the last 50,000 years in Europe with a focus on (1) a general revision of Alnus history since the Last Glacial Maximum (LGM), (2) evidence of northern refugia of Alnus populations during the LGM and (3) the specific history of Alnus in particular European regions.

METHODOLOGY

We determined changes in Alnus distribution on the basis of 811 and 68 radiocarbon-dated pollen and macrofossil sites, respectively. We compiled data from the European Pollen Database, the Czech Quaternary Palynological Database, the Eurasian Macrofossil Database and additional literature. Pollen percentage thresholds indicating expansions or retreats were used to describe patterns of past Alnus occurrence.

PRINCIPAL FINDINGS

An expansion of Alnus during the Late Glacial and early Holocene periods supports the presence of alders during the LGM in southern peninsulas and northerly areas in western Europe, the foothills of the Alps, the Carpathians and northeastern Europe. After glaciers withdrew, the ice-free area of Europe was likely colonized from several regional refugia; the deglaciated area of Scandinavia was likely colonized from a single refugium in northeastern Europe. In the more northerly parts of Europe, we found a scale-dependent pattern of Alnus expansion characterised by a synchronous increase of Alnus within individual regions, though with regional differences in the times of the expansion. In southern peninsulas, the Alps and the Carpathians, by contrast, it seems that Alnus expanded differently at individual sites rather than synchronously in whole regions.

CONCLUSIONS

Our synthesis supports the idea that northern LGM populations were important sources of postglacial Alnus expansion. The delayed Alnus expansion apparent in some regions was likely a result of environmental limitations.

METHODOLOGY

PRINCIPAL FINDINGS

CONCLUSIONS

背景/目的：最近，新的古生态学记录通过分子分析和古分布模型提供了更全面的见解，了解了最后一个第四纪循环中植物的行为。我们回顾了欧洲亚种 Alnus 物种在过去 5 万年中的迁移历史，重点关注：（1）末次冰期最大值 (LGM) 以来 Alnus 历史的综合修订，（2）LGM 期间 Alnus 种群北部避难所的证据，以及（3）Alnus 在特定欧洲地区的具体历史。

方法

我们根据 811 个和 68 个放射性碳测年的花粉和宏观化石地点，分别确定了 Alnus 分布的变化。我们从欧洲花粉数据库、捷克第四纪孢粉数据库、欧亚大陆大型化石数据库和其他文献中汇编了数据。用于描述过去 Alnus 发生模式的花粉百分比阈值指示了扩张或退缩。

主要发现

晚冰期和早全新世期间 Alnus 的扩张支持了 LGM 期间在南半岛和西欧北部地区、阿尔卑斯山山麓、喀尔巴阡山脉和东欧的存在。冰川退缩后，欧洲无冰地区可能是从几个区域避难所殖民而来的；斯堪的纳维亚的无冰地区可能是从东欧的一个单一避难所殖民而来的。在欧洲较北的地区，我们发现了一种依赖于规模的 Alnus 扩张模式，其特征是各个地区的 Alnus 同步增加，尽管扩张的时间存在区域差异。相比之下，在南半岛、阿尔卑斯山和喀尔巴阡山脉，Alnus 在各个地点的扩张似乎不同步，而不是整个地区同步扩张。