Prionospio mitogenomes and nuclear rDNA

The Prionospio generic complex comprises the most diverse and complex group within the polychaete family Spionidae. The phylogenetic relationships within the group are still poorly understood, and the generic breakdown is unstable. Several species have been considered cosmopolitan. In this study, we aimed to assess the diversity, relationships, and wider distribution of species in the Prionospio generic complex occurring in Norwegian waters. We analyzed mitochondrial genomes and nuclear ribosomal DNA assembled via whole-genome shotgun sequencing. Our study revealed the presence of four well-supported but currently undescribed species of Prionospio in Norwegian waters by molecular species delimitation algorithms. We found a novel pattern of widely distributed polychaete species in coastal waters, with some species exhibiting distribution ranges spanning just short of ten thousand kilometers. Such wide distribution parallels patterns found in species of deep sea Prionospio, which could suggest that factors beyond recent anthropogenic translocations contribute to their distribution. Our comprehensive analysis of mitochondrial genomes enabled us to construct the first well supported molecular phylogeny of the Prionospio complex. We observed polyphyly in Aurospio and paraphyly in Prionospio, indicating the need for taxonomic revisions. These findings provide valuable insights into the diversity and distribution patterns of Prionospio species, contributing to the broader understanding of marine biodiversity and ecological monitoring efforts.