Osmunda pulchella sp. nov. from the Jurassic of Sweden—reconciling molecular and fossil evidence in the phylogeny of modern royal ferns (Osmundaceae)

BMC Evolutionary Biology

Research Article

Stephen McLoughlin¹  Benjamin Bomfleur¹  Guido W. Grimm² 

[1] Department of Palaeobiology, Swedish Museum of Natural History, Stockholm, Sweden;Department of Palaeobiology, Swedish Museum of Natural History, Stockholm, Sweden;Department of Palaeontology, University of Vienna, Vienna, Austria;

关键词: Calcification;    Evolutionary placement;    Fern evolution;    Organelle preservation;    Osmundales;    Osmundastrum;    Outgroup;    Paraphyly;    Permineralization;    Phylogenetic networks;   

DOI  :  10.1186/s12862-015-0400-7

 received in 2014-12-11, accepted in 2015-06-01,  发布年份 2015

来源: Springer

【 摘 要 】

BackgroundThe classification of royal ferns (Osmundaceae) has long remained controversial. Recent molecular phylogenies indicate that Osmunda is paraphyletic and needs to be separated into Osmundastrum and Osmunda s.str. Here, however, we describe an exquisitely preserved Jurassic Osmunda rhizome (O. pulchella sp. nov.) that combines diagnostic features of both Osmundastrum and Osmunda, calling molecular evidence for paraphyly into question. We assembled a new morphological matrix based on rhizome anatomy, and used network analyses to establish phylogenetic relationships between fossil and extant members of modern Osmundaceae. We re-analysed the original molecular data to evaluate root-placement support. Finally, we integrated morphological and molecular data-sets using the evolutionary placement algorithm.ResultsOsmunda pulchella and five additional Jurassic rhizome species show anatomical character suites intermediate between Osmundastrum and Osmunda. Molecular evidence for paraphyly is ambiguous: a previously unrecognized signal from spacer sequences favours an alternative root placement that would resolve Osmunda s.l. as monophyletic. Our evolutionary placement analysis identifies fossil species as probable ancestral members of modern genera and subgenera, which accords with recent evidence from Bayesian dating.ConclusionsOsmunda pulchella is likely a precursor of the Osmundastrum lineage. The recently proposed root placement in Osmundaceae—based solely on molecular data—stems from possibly misinformative outgroup signals in rbcL and atpA genes. We conclude that the seemingly conflicting evidence from morphological, anatomical, molecular, and palaeontological data can instead be elegantly reconciled under the assumption that Osmunda is indeed monophyletic.

【 授权许可】

CC BY   
© Bomfleur et al. 2015