School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland.
Proc Natl Acad Sci U S A. 2010 Aug 31;107(35):15351-6. doi: 10.1073/pnas.1004207107. Epub 2010 Aug 16.
Macrofossils (mostly leaves) and sporomorphs (pollen and spores) preserve conflicting records of plant biodiversity during the end-Permian (P-Tr), Triassic-Jurassic (Tr-J), and end-Cretaceous (K-T) mass extinctions. Estimates of diversity loss based on macrofossils are typically much higher than estimates of diversity loss based on sporomorphs. Macrofossils from the Tr-J of East Greenland indicate that standing species richness declined by as much as 85% in the Late Triassic, whereas sporomorph records from the same region, and from elsewhere in Europe, reveal little evidence of such catastrophic diversity loss. To understand this major discrepancy, we have used a new high-resolution dataset of sporomorph assemblages from Astartekløft, East Greenland, to directly compare the macrofossil and sporomorph records of Tr-J plant biodiversity. Our results show that sporomorph assemblages from the Tr-J boundary interval are 10-12% less taxonomically diverse than sporomorph assemblages from the Late Triassic, and that vegetation composition changed rapidly in the boundary interval as a result of emigration and/or extirpation of taxa rather than immigration and/or origination of taxa. An analysis of the representation of different plant groups in the macrofossil and sporomorph records at Astartekløft reveals that reproductively specialized plants, including cycads, bennettites and the seed-fern Lepidopteris are almost absent from the sporomorph record. These results provide a means of reconciling the macrofossil and sporomorph records of Tr-J vegetation change, and may help to understand vegetation change during the P-Tr and K-T mass extinctions and around the Paleocene-Eocene Thermal Maximum.
大型化石（主要是叶子）和孢粉（花粉和孢子）在二叠纪末（P-Tr）、三叠纪-侏罗纪（Tr-J）和白垩纪末（K-T）大灭绝期间保存了植物生物多样性的相互矛盾的记录。基于大型化石的多样性损失估计通常远高于基于孢粉的多样性损失估计。格陵兰东海岸 Tr-J 的大型化石表明，晚三叠世时现存物种丰富度下降了多达 85%，而来自同一地区和欧洲其他地区的孢粉记录几乎没有这种灾难性多样性损失的证据。为了理解这种主要差异，我们使用了来自格陵兰东 Astartekløft 的孢粉组合的新高分辨率数据集，直接比较 Tr-J 植物生物多样性的大型化石和孢粉记录。我们的结果表明，Tr-J 边界间隔的孢粉组合在分类上比晚三叠世的孢粉组合少 10-12%，并且由于移民和/或灭绝的分类群而导致植被组成在边界间隔内迅速变化，而不是移民和/或起源的分类群。对 Astartekløft 的大型化石和孢粉记录中不同植物群的代表性的分析表明，生殖特化的植物，包括苏铁、本内苏铁和种子蕨类植物 Lepidopteris，几乎不存在于孢粉记录中。这些结果提供了一种协调 Tr-J 植被变化的大型化石和孢粉记录的方法，并可能有助于理解 P-Tr 和 K-T 大灭绝期间以及古新世-始新世极热时期的植被变化。
