Molecular assessment of the tribes Streblocladieae and Polysiphonieae (Rhodomelaceae, Rhodophyta) in the British Isles reveals new records and species that require taxonomic revision Author Piñeiro-Corbeira, Cristina Coastal Biology Research Group, Faculty of Sciences and Centre for Advanced Scientific Research (CICA), University of A Coruña, 15071, A Coruña (Spain) Author Maggs, Christine A. Queen’s University Belfast, Marine Laboratory, Portaferry, Newtownards BT 22 1 PF (United Kingdom) Author Rindi, Fabio Dipartimento di Scienze della Vita e dell’Ambiente, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona (Italy) Author Bunker, Francis MarineSeen, Estuary Cottage, Bentlass, Hundleton, Pembrokeshire, Wales SA 71 5 RN (United Kingdom) Author Baldock, Lin Dorset Wildlife Trust, Brooklands Farm, Forston, Dorchester DT 2 7 AA (United Kingdom) Author Díaz-Tapia, Pilar Coastal Biology Research Group, Faculty of Sciences and Centre for Advanced Scientific Research (CICA), University of A Coruña, 15071, A Coruña (Spain) and Instituto Español de Oceanografía (IEO), Centro Oceanográfico de A Coruña, Aptdo. 130, 15080, A Coruña (Spain) pdiaz @ udc. es (corresponding author) pdiaz@udc.es text Cryptogamie, Algologie 2020 2020-06-05 20 8 55 72 journal article 246880 10.5252/cryptogamiealgologie2020v41a8 380efeb5-6e5b-4c5d-9edf-fb35647c83c6 1776-0992 7827761 Vertebrata simulans (Harvey) Kuntze and Polysiphonia ceramiiformis P.Crouan & H.Crouan MOLECULAR IDENTIFICATION Two rbc L sequences for Vertebrata simulans and three for Polysiphonia ceramiiformis from the British Isles (four of which were newly determined) were identical, and also identical to a newly determined sequence of P.ceramiiformis from Spain . These sequences were resolved in the phylogeny in a highly supported clade including eight other members of the genus Vertebrata ( Fig. 2 ). Relationships among members of the clade including V. simulans were unresolved. The most closely related species in the phylogeny is V. byssoides (Goodenough & Woodward) Kuntze with 5.3% divergence in the rbc L gene. Two cox 1 sequences were generated for both V. simulans and P.ceramiiformis . The three sequences from the United Kingdom including specimens morphologically identified as V.simulans and P. ceramiiformis were identical, while the sequence of P.ceramiiformis from Spain differed by 1 bp from the British specimens. MORPHOLOGICAL OBSERVATIONS Vertebrata simulans and Polysiphonia ceramiiformis are predominantly erect ( Fig. 3A, D ), attached to their substratum by short prostrate axes with unicellular rhizoids that are cut off from the pericentral cells. They have ecorticate axes with 10-13pericentral cells. Axes are 100-300 µm in diameter, with segments 0.3-0.8 L/D (length/diameter). Branches are formed mostly every 2-9 segments, replacing trichoblasts. Polysiphonia ceramiiformis has a soft succulent texture and branches form corymbose , characteristically forcipate apices ( Fig.3 A-C). Vertebrata simulans is more slender and, in addition to indeterminate branches, it has abundant branchlets that remain short and spine-like ( Fig. 3 D-F). Reproductive structures were not observed in specimens of P.ceramiiformis studied here, but tetrasporangia,spermatangia and cystocarps were described in Maggs & Hommersand (1993) . Vertebrata simulans has tetrasporangia 40-70 µm in diameter, formed in short lateral branchlets, in short spiral series ( Fig. 3G ). Sexual reproductive structures are unknown except for the observation of spermatangia on a tetrasporophyte ( Maggs & Hommersand 1993 ).