A phylogenetic analysis of the polychaeta based on mitochondrial CO1 and 16S rRNA gene sequences

Annelids, a phylum of segmented worms, are a diverse group inhabiting terrestrial, freshwater, and marine environments. Recent molecular studies challenge traditional classifications, revealing the inclusion of taxa like Echiura, Sipuncula, and non-monophyletic relationships within the group. This study utilized mitochondrial cytochrome c oxidase I (CO1) and 16S ribosomal RNA (16S rRNA) gene sequences to construct phylogenetic trees for 50 Polychaeta species using maximum likelihood analysis. CO1 gene exhibited limitations in phylogenetic relationship, while 16S rRNA excelled in elucidating broader taxonomic relationships with strong support for evolutionary relationships. Results reaffirmed the non-monophyly of Polychaeta and highlighted their distinct evolutionary patterns, such as independent lineage development within the Polynoidae family. These findings contribute to understanding polychaete diversity and evolutionary history, emphasizing the need for integrating multiple molecular markers for comprehensive phylogenetic analysis.