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

Bomfleur B, Grimm GW, McLoughlin S - BMC Evol. Biol. (2015)

Bottom Line: Osmunda 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Palaeobiology, Swedish Museum of Natural History, Stockholm, Sweden. benjamin.bomfleur@nrm.se.

ABSTRACT

Background: The 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.

Results: Osmunda 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.

Conclusions: Osmunda 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.

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Osmunda pulchella sp. nov. from the Lower Jurassic of Skåne, southern Sweden. Holotype. a Reproduction of the only available print of the original holotype material prior to preparation, showing the gross morphology of the rhizome. b, c Transverse sections through center (B: NRM-S069656) and apex (C: NRM-S069657) of the rhizome. d Longitudinal section through the rhizome (NRM-S069658). (E) Detail of Fig. 1B. Scale bars: (a–c) = 5 mm; (d, e) = 2 mm
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Fig1: Osmunda pulchella sp. nov. from the Lower Jurassic of Skåne, southern Sweden. Holotype. a Reproduction of the only available print of the original holotype material prior to preparation, showing the gross morphology of the rhizome. b, c Transverse sections through center (B: NRM-S069656) and apex (C: NRM-S069657) of the rhizome. d Longitudinal section through the rhizome (NRM-S069658). (E) Detail of Fig. 1B. Scale bars: (a–c) = 5 mm; (d, e) = 2 mm

Mentions: The holotype is a calcified rhizome fragment about 6 cm long and up to 4 cm in diameter (Fig. 1a–c). It consists of a small central stem that is surrounded by a compact mantle of helically arranged, persistent petiole bases and interspersed rootlets (Fig. 1b, e). The rootlets extend outwards through the mantle in a sinuous course almost perpendicular to the axis, indicating low rhizomatous rather than arborescent growth; the asymmetrical distribution of roots in longitudinal sections of the rhizome (Fig. 1d) points to a creeping habit.Fig. 1


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

Bomfleur B, Grimm GW, McLoughlin S - BMC Evol. Biol. (2015)

Osmunda pulchella sp. nov. from the Lower Jurassic of Skåne, southern Sweden. Holotype. a Reproduction of the only available print of the original holotype material prior to preparation, showing the gross morphology of the rhizome. b, c Transverse sections through center (B: NRM-S069656) and apex (C: NRM-S069657) of the rhizome. d Longitudinal section through the rhizome (NRM-S069658). (E) Detail of Fig. 1B. Scale bars: (a–c) = 5 mm; (d, e) = 2 mm
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4487210&req=5

Fig1: Osmunda pulchella sp. nov. from the Lower Jurassic of Skåne, southern Sweden. Holotype. a Reproduction of the only available print of the original holotype material prior to preparation, showing the gross morphology of the rhizome. b, c Transverse sections through center (B: NRM-S069656) and apex (C: NRM-S069657) of the rhizome. d Longitudinal section through the rhizome (NRM-S069658). (E) Detail of Fig. 1B. Scale bars: (a–c) = 5 mm; (d, e) = 2 mm
Mentions: The holotype is a calcified rhizome fragment about 6 cm long and up to 4 cm in diameter (Fig. 1a–c). It consists of a small central stem that is surrounded by a compact mantle of helically arranged, persistent petiole bases and interspersed rootlets (Fig. 1b, e). The rootlets extend outwards through the mantle in a sinuous course almost perpendicular to the axis, indicating low rhizomatous rather than arborescent growth; the asymmetrical distribution of roots in longitudinal sections of the rhizome (Fig. 1d) points to a creeping habit.Fig. 1

Bottom Line: Osmunda 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Palaeobiology, Swedish Museum of Natural History, Stockholm, Sweden. benjamin.bomfleur@nrm.se.

ABSTRACT

Background: The 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.

Results: Osmunda 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.

Conclusions: Osmunda 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.

Show MeSH