Molecular and phylogenetic analyses support the establishment of the new genus Neoverlaquea gen. nov. (Rhodophyta, Ceramiales, Rhodomelaceae) for the Mediterranean Polysiphonia sertularioides

Within the family Rhodomelaceae several taxa exhibit significant cryptic diversity and high phenotypic plasticity, requiring the employment of molecular data for the accurate delimitation of genera and species. Among these, the genus Polysiphonia sensu lato has been demonstrated to be polyphyletic, and several new genera have been separated from it over time. This study focuses on Polysiphonia sertularioides, a species with apparently worldwide distribution and a still uncertain taxonomic position. Indeed, previous molecular studies have indicated cryptic diversity within this species and the distinction of several P. sertularioides lineages within the family Rhodomelaceae. Aimed at resolving the taxonomic status of P. sertularioides, morphological and molecular analyses (rbcL and cox1 genes) were carried out on specimens attributable to this taxon and collected from the Mediterranean Sea, including sites near the probable type locality. The obtained results highlight that the Mediterranean P. sertularioides specimens form a phylogenetically well-supported clade, clearly separated from Polysiphonia sensu stricto and from the other Rhodomelacean genera so far described. This result allowed us to propose the establishment of the new genus Neoverlaquea and the new combination Neoverlaquea sertularioides to encompass this group of specimens. Detailed observation of Neoverlaquea morpho-reproductive characters and comparison with the P. sertularioides descriptions published so far allowed us also to find the unique phenotypic traits characterizing this new genus. Moreover, our phylogenetic results confirmed the existence of several phylogenetically distinct extra-Mediterranean lineages morphologically attributed to P. sertularioides, which require further investigation to be correctly identified.