Spiralian phylogeny informs the evolution of microscopic lineages
Christopher E Laumer1, Nicolas Bekkouche2, Alexandra Kerbl2
1Department of Organismic and Evolutionary Biology, Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, MA 02138, USA.
Current Biology : CB
|July 28, 2015
Summary
Microscopic animals like Diurodrilus and Lobatocerebrum are confirmed as annelids, while Micrognathozoa is the sister group to Rotifera. This study clarifies metazoan evolutionary history and the origins of Spiralia.
Area of Science:
- Zoology
- Evolutionary Biology
- Phylogenomics
Background:
- Metazoan evolutionary history is advancing, yet microscopic lineages remain understudied.
- Micrognathozoa, Loricifera, Diurodrilus, and Lobatocerebrum possess unique traits relevant to morphological evolution.
- Their phylogenetic positions and relationships to Annelida and other spiralians are uncertain.
Purpose of the Study:
- To resolve the interrelationships among meiofaunal and macrofaunal members of Spiralia.
- To clarify the evolutionary placement of microscopic animal groups.
- To assess the concept of a microscopic, acoelomate, direct-developing ancestor of Spiralia.
Main Methods:
- Phylogenomic analysis using 402 orthologs.
- Data mined from genome and transcriptome assemblies of 90 taxa.
- Analyses employed site-heterogeneous substitution models.
Main Results:
- Lobatocerebrum and Diurodrilus are nested within Annelida.
- Micrognathozoa is the sister group to Rotifera.
- Loricifera + Priapulida form the sister group to Ecdysozoa, and a lophophorate clade is recovered.
Conclusions:
- This study provides robust phylogenetic placements for several microscopic animal lineages.
- It refines our understanding of Spiralia's early diversification and the evolution of key animal groups.
- The findings challenge previous assumptions about the ancestral characteristics of Spiralia.
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