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, Bryologie 2020 2020-06-05 20 8 55 72 journal article 10.5252/cryptogamiealgologie2020v41a8 380efeb5-6e5b-4c5d-9edf-fb35647c83c6 1776-0992 7827761 Polysiphonia morrowii Harvey MOLECULAR IDENTIFICATION In total, 51 rbc L sequences have been published for Polysiphonia morrowii including data from both regions where the species is considered native (eastern Asia) and introduced. Two new sequences have been obtained for specimens from the British Isles: one from Plymouth ( England ) and one from Alderney (Channel Islands). Overall, the sequences available represent 14 rbc L haplotypes ( Fig. 2 ), with a sequence divergence of up to 0.5% (9 bp). The sequence from Plymouth was identical to specimens from western Asia, Australasia, Pacific and Atlantic South America and Atlantic France , while the sequence from Alderney represents a new haplotype. Polysiphonia morrowii was placed in the phylogeny in a highly supported clade with P. stricta , the generitype ( Fig. 2 ). The nearest neighbour of P. morrowii was P. pacifica (AY958162) from which it diverged by 2.9-3.2%. FIG. 5. — Vertebrata tripinnata (J.Agardh) Kuntze : A , habit; B , rhizoid cut off from pericentral cells ( arrowhead ); C , cross-section of a prostrate axes with a rhizoid cut off from pericentral cells ( arrowhead ); D , cross-section of an axis with 18 pericentral cells; E , upper parts of erect axes with short branches and long apical trichoblasts; F , trichoblast with multinucleate cells; G , scar cells of trichoblasts spirally arranged on every segment ( arrowheads ). Scale bars:A,10 mm;B, 100 µm; C, 100 µm; D, 50 µm; E, 500 µm; F, 50 µm; G, 100 µm. MORPHOLOGICAL OBSERVATIONS Thalli forming tufts, up to 10 cm high, with interwoven prostrate axes and erect axes spirally branched mostly every five segments ( Fig. 6A, B ). Axes ecorticate and with four pericentral cells. Erect axes growing from sharply pointed apical cells ( Fig. 6C ), increasing to 40-65 µm in diameter in mid parts; segments 1.2-3.6 L/D. Trichoblasts not observed. Tetrasporangia formed in the last 2-3 branching orders in straight series ( Fig. 6D ), 20-30 µm in diameter. Sexual reproductive structures were not observed.