A Burmese amber fossil of Radula (Porellales, Jungermanniopsida) provides insights into the Cretaceous evolution of epiphytic lineages of leafy liverworts
A Burmese amber fossil of Radula (Porellales, Jungermanniopsida) provides insights into the Cretaceous evolution of epiphytic lineages of leafy liverworts
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DOI：
10.5194/fr-20-201-2017
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发表时间：
2017-07-27
期刊：
影响因子：
1.4
通讯作者：
Heinrichs, Jochen
中科院分区：
文献类型：
--
作者：
Bechteler, Julia;Schmidt, Alexander R.;Heinrichs, Jochen
基于 DNA 的分化时间估计表明白垩纪期间地钱附生谱系的组成发生了重大变化；然而，来自化石记录的证据却很少。我们展示了第一个白垩纪化石，主要是附生叶叶苔属拉杜拉（Radula）。 100 马币老缅甸琥珀。该化石的精美保存使我们能够首次了解裸子植物占主导地位的森林中出现的齿舌早期冠群代表的形态。祖先特征状态重建将化石与齿舌亚科的冠群对齐。齿托拉杜拉；然而，使用软件 BEAST 进行相应的分歧时间估计会导致不切实际的老年估计。或者，将化石分配给 subg 的茎。 Odontoradula 的齿根年龄估计为 227.8Ma（95% 最高后密度（HPD）：165.7-306.7），冠组估计为 176.3Ma（135.1-227.4），与采用标准替代率的分析一致（茎年龄 235.6 Ma（142.9-368.5），冠组年龄） 183.8马(109.9-289.1))。该化石可能属于齿舌亚科的茎谱系。齿托拉杜拉。该化石的现代形态表明，附生苔类植物从裸子植物到被子植物的转变并未发生植物体结构的变化。该化石为当时惊人的形态同质性提供了证据。即使是保守的化石节点分配也支持对齿根冠群的较旧年龄的估计，而不是较年轻的年龄估计，涉及白垩纪末大多数现存亚属的起源以及新生代冠群的多样化。
DNA-based divergence time estimates suggested major changes in the composition of epiphyte lineages of liverworts during the Cretaceous; however, evidence from the fossil record is scarce. We present the first Cretaceous fossil of the predominantly epiphytic leafy liverwort genus Radula in ca. 100 Myr old Burmese amber. The fossil's exquisite preservation allows first insights into the morphology of early crown group representatives of Radula occurring in gymnosperm-dominated forests. Ancestral character state reconstruction aligns the fossil with the crown group of Radula subg. Odontoradula; however, corresponding divergence time estimates using the software BEAST lead to unrealistically old age estimates. Alternatively, assignment of the fossil to the stem of subg. Odontoradula results in a stem age estimate of Radula of 227.8Ma (95% highest posterior density (HPD): 165.7-306.7) and a crown group estimate of 176.3Ma (135.1-227.4), in agreement with analyses employing standard substitution rates (stem age 235.6 Ma (142.9-368.5), crown group age 183.8 Ma (109.9-289.1)). The fossil likely belongs to the stem lineage of Radula subg. Odontoradula. The fossil's modern morphology suggests that switches from gymnosperm to angiosperm phorophytes occurred without changes in plant body plans in epiphytic liverworts. The fossil provides evidence for striking morphological homoplasy in time. Even conservative node assignments of the fossil support older rather than younger age estimates of the Radula crown group, involving origins for most extant subgenera by the end of the Cretaceous and diversification of their crown groups in the Cenozoic.