MicroRNAs resolve an apparent conflict between annelid systematics and their fossil record

Both the monophyly and inter-relationships of the major annelid groups have remained uncertain, despite intensive research on both morphology and molecular sequences. Morphological cladistic analyses indicate that Annelida is monophyletic and consists of two monophyletic groups, the clitellates and...

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Bibliographic Details
Published in:Proceedings of the Royal Society. B, Biological sciences Biological sciences, 2009-12, Vol.276 (1677), p.4315-4322
Main Authors: Sperling, Erik A., Vinther, Jakob, Moy, Vanessa N., Wheeler, Benjamin M., Sémon, Marie, Briggs, Derek E. G., Peterson, Kevin J.
Format: Article
Language:English
Subjects:
Animals
Annelida
Annelida - anatomy & histology
Annelida - classification
Annelida - genetics
Base Sequence
Blotting, Northern
Fossils
Genomes
Lumbricus
Marine
Materials
MicroRNA
MicroRNAs - genetics
Molecular Palaeobiology
Molecular Sequence Data
Mollusks
Monophyly
Non-Coding Rna
Phylogenetics
Phylogeny
RNA
Sequence Analysis, DNA
Small libraries
Taxa
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Summary:Both the monophyly and inter-relationships of the major annelid groups have remained uncertain, despite intensive research on both morphology and molecular sequences. Morphological cladistic analyses indicate that Annelida is monophyletic and consists of two monophyletic groups, the clitellates and polychaetes, whereas molecular phylogenetic analyses suggest that polychaetes are paraphyletic and that sipunculans are crown-group annelids. Both the monophyly of polychaetes and the placement of sipunculans within annelids are in conflict with the annelid fossil record-the former because Cambrian stem taxa are similar to modern polychaetes in possessing biramous parapodia, suggesting that clitellates are derived from polychaetes; the latter because although fossil sipunculans are known from the Early Cambrian, crown-group annelids do not appear until the latest Cambrian. Here we apply a different data source, the presence versus absence of specific microRNAs-genes that encode approximately 22 nucleotide non-coding regulatory RNAs-to the problem of annelid phylogenetics. We show that annelids are monophyletic with respect to sipunculans, and polychaetes are paraphyletic with respect to the clitellate Lumbricus, conclusions that are consistent with the fossil record. Further, sipunculans resolve as the sister group of the annelids, rooting the annelid tree, and revealing the polarity of the morphological change within this diverse lineage of animals.
ISSN:0962-8452
1471-2954
1471-2945
DOI:10.1098/rspb.2009.1340