Phylogenomics resolves ambiguous relationships within Aciculata (Errantia, Annelida)

Area of Science:

• Marine biology
• Evolutionary biology
• Genomics

Background:

• Aciculata (Eunicida + Phyllodocida) is a major annelid clade, yet its phylogeny is poorly understood due to limited sampling in previous studies.
• The phylogenetic placement of many Phyllodocida clades remains particularly challenging.
• This research addresses the need for a more comprehensive understanding of annelid evolutionary history.

Purpose of the Study:

• To resolve the phylogenetic relationships within the annelid clade Aciculata using a large-scale phylogenomic analysis.
• To include underrepresented and enigmatic taxa to improve phylogenetic resolution.
• To provide a robust phylogenetic framework for understanding annelid systematics and evolution.

Main Methods:

• Conducted a large-scale phylogenomic analysis using 24 transcriptomes, including 13 newly generated datasets.
• Focused on broad taxonomic sampling within Aciculata, incorporating problematic and understudied groups.
• Employed phylogenetic methods to analyze sequence data and infer evolutionary relationships.

Main Results:

• Established a robust phylogeny for Aciculata, reinstating names within Eunicida (Eunicoidea, Oenonoidea) and delineating new clades within Phyllodocida (Phyllodociformia, Glyceriformia, Nereidiformia, Nephtyiformia, Aphroditiformia).
• Phyllodociformia now includes Lacydonia, Typhloscolecidae, Lopadorrhynchidae, and Phyllodocidae; Nephtyiformia includes Nephtyidae and Pilargidae.
• Glyceriformia is broadened to encompass Sphaerodoridae, Tomopteridae, and Glyceroidea, and the study identifies confounding signals causing conflicting gene tree topologies.

Conclusions:

• The study provides a resolved phylogeny for Aciculata, impacting annelid systematics and classification.
• New systematic arrangements are proposed, including redefined and newly delineated clades within Phyllodocida and Eunicida.
• The research underscores the importance of comprehensive sampling and highlights challenges posed by conflicting phylogenetic signals in phylogenomic analyses.