ABSTRACT

Diospyros is a large genus of woody flowering plants with a predominantly subtropical and tropical modern distribution. Fossils attributed to Diospyros are mainly leaf impressions from Cretaceous and Cenozoic strata across the Northern Hemisphere. However, it is difficult to assign such fossils to Diospyros because genus-diagnostic leaf characteristics remain to be identified. Unequivocal fossil records of Diospyros are few, including staminate flowers with in situ pollen from the late Eocene of South Australia and dispersed pollen from Cenozoic strata in the Northern Hemisphere. Here, we investigated dispersed pollen and calyx remains from Miocene deposits of Denmark using a combined scanning electron/light microscopy approach. Tricolporate, relatively large pollen with lalongate pori and long bow-shaped colpi and a distinctive micro/nanorugulate exine ornamentation together with persistent 4-lobed flower calyces allow unambiguous identification of the genus. Based on the large size of the calyx, we describe a new fossil-species of Diospyros. Further, a review of the fossil pollen record of Diospyros shows that, in addition to the Australian record, the genus was present in South China, western North America and Europe during the Eocene and in East and South Africa and Central Asia during the Oligo-Miocene. Although still scanty, the pollen record can contribute vital information for time-calibrated molecular phylogenies to resolve conflicting biogeographic inferences. A thorough description of the historical biogeography of Diospyros is still in its infancy. While we initiate such a study here, development of a comprehensive picture will require further studies of dispersed pollen grains with high taxonomic resolution.

摘要

Diospyros是一大类木本开花植物，主要​​分布于亚热带和热带现代地区。Diospyros 的化石主要是来自北半球白垩纪和新生代地层的叶印。然而，很难将这些化石归于柿属，因为属诊断的叶子特征仍有待确定。柿子的明确化石记录很少，包括原位雄花来自南澳大利亚始新世晚期的花粉和来自北半球新生代地层的分散花粉。在这里，我们使用组合扫描电子/光学显微镜方法研究了丹麦中新世沉积物中分散的花粉和花萼残骸。Tricolporate，相对较大的花粉，带有长条形孔和长弓形colpi，独特的微/纳米线状外壁装饰以及持久的4裂花萼允许明确识别该属。基于花萼的大尺寸，我们描述了一种新的柿属化石种。此外，对柿属花粉化石记录的回顾表明，除了澳大利亚的记录外，该属还在始新世期间出现在华南、北美西部和欧洲，以及在渐新世期间出现在东、南非和中亚。尽管仍然很少，但花粉记录可以为时间校准的分子系统发育提供重要信息，以解决相互矛盾的生物地理推断。对柿子的历史生物地理的全面描述仍处于起步阶段。虽然我们在这里开始了这样的研究，但全面的发展将需要对具有高分类分辨率的分散花粉粒进行进一步研究。