Lóriga Josmaily, Schmidt Alexander R, Moran Robbin C, Feldberg Kathrin, Schneider Harald, Heinrichs Jochen
University of Munich (LMU), Systematic Botany and Mycology, Menzinger Str. 67, 80638 Munich, Germany.
University of Göttingen, Courant Research Centre Geobiology, Goldschmidtstraße 3, 37077 Göttingen, Germany.
Am J Bot. 2014 Sep;101(9):1466-75. doi: 10.3732/ajb.1400262. Epub 2014 Sep 17.
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Closing gaps in the fossil record and elucidating phylogenetic relationships of mostly incomplete fossils are major challenges in the reconstruction of the diversification of fern lineages through time. The cosmopolitan family Dryopteridaceae represents one of the most species-rich families of leptosporangiate ferns, yet its fossil record is sparse and poorly understood. Here, we describe a fern inclusion in Miocene Dominican amber and investigate its relationships to extant Dryopteridaceae.•
The morphology of the fossil was compared with descriptions of extant ferns, resulting in it being tentatively assigned to the bolbitidoid fern genus Elaphoglossum. This assignment was confirmed by reconstructing the evolution of the morphological characters preserved in the inclusion on a molecular phylogeny of 158 extant bolbitidoid ferns. To assess the morphology-based assignment of the fossil to Elaphoglossum, we examined DNA-calibrated divergence time estimates against the age of the amber deposits from which it came.•
The fossil belongs to Elaphoglossum and is the first of a bolbitidoid fern. Its assignment to a particular section of Elaphoglossum could not be determined; however, sects. Lepidoglossa, Polytrichia, and Setosa can be discounted because the fossil lacks subulate scales or scales with acicular marginal hairs. Thus, the fossil might belong to either sects. Amygdalifolia, Wrightiana, Elaphoglossum, or Squamipedia or to an extinct lineage.•
The discovery of a Miocene Elaphoglossum fossil provides remarkable support to current molecular clock-based estimates of the diversification of these ferns.
研究前提：填补化石记录中的空白并阐明大多不完整化石的系统发育关系，是通过时间重建蕨类植物谱系多样化的主要挑战。广布的鳞毛蕨科是薄囊蕨纲中物种最丰富的科之一，但其化石记录稀少且了解不足。在此，我们描述了一块中新世多米尼加琥珀中的蕨类植物内含物，并研究其与现存鳞毛蕨科的关系。
方法：将化石的形态与现存蕨类植物的描述进行比较，初步将其归为鳞毛蕨类的舌蕨属。通过在158种现存鳞毛蕨类植物的分子系统发育树上重建内含物中保存的形态特征的进化，证实了这一归类。为评估基于形态学将化石归为舌蕨属的归类，我们对照其来源的琥珀沉积物的年龄，检查了经DNA校准的分歧时间估计。
主要结果：该化石属于舌蕨属，是鳞毛蕨类的首个化石。无法确定它属于舌蕨属的哪个特定组；然而，由于化石缺乏钻形鳞片或边缘有针状毛的鳞片，可排除鳞叶组、多毛组和刚毛组。因此，该化石可能属于杏仁叶组、赖特组、舌蕨组或鳞瓣组，或者属于一个已灭绝的谱系。
结论：中新世舌蕨属化石的发现为当前基于分子钟的这些蕨类植物多样化估计提供了显著支持。
