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Acoel flatworms are not platyhelminthes: evidence from phylogenomics
Hervé Philippe1, Henner Brinkmann, Pedro Martinez
1Canadian Institute for Advanced Research, Centre Robert-Cedergren, Département de Biochimie, Université de Montréal, Montréal, Québec, Canada. herve.philippe@umontreal.ca
Acoel flatworms are not Platyhelminthes but early Bilateria. Phylogenomic analysis suggests a deuterostome affinity, challenging traditional classifications and requiring further research for definitive placement.
Area of Science:
- Marine Biology
- Evolutionary Biology
- Phylogenetics
Background:
- Acoel flatworms were traditionally classified within Platyhelminthes.
- Recent molecular data suggested acoels represent early-diverging Bilateria, but this was questioned due to potential long branch attraction (LBA) artifacts.
Purpose of the Study:
- To re-examine the phylogenetic position of acoel flatworms using a phylogenomic approach.
- To clarify the evolutionary relationships of acoels and their placement within Metazoa.
Main Methods:
- Phylogenomic analysis of 68 protein-coding genes from Convoluta pulchra and 51 other metazoan species.
- Utilized the CAT mixture model, known to overcome LBA artifacts.
Main Results:
- Results unequivocally show acoels are not part of Platyhelminthes, rendering the latter polyphyletic.
- Phylogenetic analysis indicates a deuterostome affinity for acoels, potentially sister to various deuterostome clades.
- Weak support for deuterostome nodes and fast evolutionary rate of C. pulchra highlight limitations.
Conclusions:
- Acoels are confirmed to be outside Platyhelminthes, necessitating a redefinition of this phylum.
- The deuterostome affinity of acoels requires further investigation with data from slowly evolving acoels or nemertodermatids.
Related Concept Videos
Diversity of Protists IV
Diversity of Protists I
Diversity of Protists II
Diversity of Protists III
Phylogeny
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