Department of Paleobiology, Swedish Museum of Natural History, Stockholm, Sweden.
Aerobiology and Pollen Information, Medical University of Vienna, Vienna, Austria.
Am J Bot. 2021 Aug;108(8):1500-1524. doi: 10.1002/ajb2.1716. Epub 2021 Aug 29.
The Fagaceae comprise around 1000 tree species in the Northern Hemisphere. Despite an extensive fossil pollen record, reconstructing biogeographic patterns is hampered because it is difficult to achieve good taxonomic resolution with light microscopy alone. We investigate dispersed pollen of Fagaceae from the Miocene Søby flora, Denmark. We explore the latitudinal gradient in Fagaceae distribution during the Miocene Climatic Optimum (MCO) in Europe and the Northern Hemisphere to compare it with the Eocene Warmhouse and the present.
We investigated dispersed pollen using light and scanning electron microscopy. We assessed biogeographic patterns in Fagaceae during two warm periods in Earth history (MCO, Eocene) and the present.
Eight species of Fagaceae were recognized in the Søby flora. Of these, Fagus had a continuous Mediterranean to subarctic distribution during MCO; Quercus sect. Cerris and castaneoids had northern limits in Denmark, and evergreen Quercus sect. Ilex in Central Europe. In a northern hemispheric context, Fagus and sections of Quercus had more northerly distribution limits during Eocene and MCO with maximum northward extensions during Eocene (Fagus, castaneoids) or Oligo-Miocene (Quercus sects. Cerris and Ilex). The known distribution of the extinct Tricolporopollenites theacoides during MCO included Central Europe and East China, while this taxon thrived in South China during Eocene.
More northerly distributions during MCO and Eocene probably were determined by temperature. In contrast, fossil occurrences in areas that are arid or semi-humid today were determined by maritime conditions in these areas (western North America, Central Asia) during the Cenozoic.
壳斗科包含约 1000 种北半球的乔木物种。尽管有广泛的化石花粉记录，但重建生物地理格局受到阻碍，因为仅用光学显微镜很难实现良好的分类分辨率。我们研究了丹麦 Miocene Søby 植物群中分散的壳斗科花粉。我们探讨了 Miocene 气候最佳期（MCO）期间欧洲和北半球壳斗科分布的纬度梯度，并将其与始新世温暖期和现今进行比较。
我们使用光学和扫描电子显微镜研究了分散的花粉。我们评估了地球历史上两个温暖时期（MCO、始新世）和现今壳斗科的生物地理格局。
在 Søby 植物群中识别出了 8 种壳斗科物种。其中，在 MCO 期间，山毛榉属具有从地中海到亚北极的连续分布；栎属 Quercus sect. Cerris 和山毛榉属具有在丹麦的北部界限，而常绿栎属 Quercus sect. Ilex 则在中欧。在北半球范围内，在始新世和 MCO 期间，山毛榉属和栎属部分种的分布范围更北，在始新世（山毛榉属、山毛榉属）或渐新世-中新世（栎属 Quercus sect. Cerris 和 Ilex）达到最大向北延伸。在 MCO 期间，已知灭绝的三孔花粉 Tricolporopollenites theacoides 的分布范围包括中欧和东亚，而在始新世期间，该类群在华南地区大量存在。
在 MCO 和始新世期间分布范围更北可能是由温度决定的。相比之下，在新生代，现今干旱或半湿润地区的化石出现是由这些地区的海洋条件决定的（北美西部、中亚）。
