Phylogenetic and Mitogenomic Insights of Acrocirridae (Cirratuliformia; Annelida): A Trans-Pacific Range Extension, New Genus, and Four New Species

Understanding the diversity, phylogenetic relationships, and evolutionary transitions within Acrocirridae, a clade of polychaete worms, is crucial for unraveling the complexities of benthic-pelagic evolutionary transitions in marine ecosystems. In this study, we describe four new species, erect a new genus to accommodate two of these species, and provide an updated phylogeny for Acrocirridae. Additionally, we assemble complete mitogenomes and present the first mitogenome phylogeny for the broader Cirratuliformia, offering valuable insights into the genetic characteristics and evolutionary history of benthic and pelagic species. The new species described in this study significantly contribute to the known diversity within Acrocirridae.Furthermore, the establishment of a new genus highlights the importance of taxonomic revisions in capturing the true evolutionary relationships and diversification patterns within this clade. Our updated phylogeny for Acrocirridae incorporates both morphological and molecular data, providing a comprehensive understanding of relationships. By assembling complete mitogenomes, we unravel the genetic composition and mitochondrial gene arrangement of key taxa within Cirratuliformia. This dataset serves as a valuable resource for future studies investigating the genomic features and evolutionary dynamics within this group of polychaetes. Importantly, our mitogenome-based phylogeny reveals variation in gene arrangements and codon usage. Overall, this study provides a comprehensive investigation of the diversity, phylogeny, and evolutionary transitions within Acrocirridae. Our findings enhance our understanding of the genetic and ecological factors driving benthic-pelagic transitions in polychaete evolution and provides a framework for future research.