Two new species of Polysiphonia (Ceramiales, Florideophyceae) from the western Atlantic

Abstract

Abstract Integrated morphological and molecular analyses of Polysiphonia species revealed that two western Atlantic species identified as P. denudata and P. urceolata (=P. stricta) represent undescribed taxa. Polysiphonia schneideri sp. nov. is proposed for specimens previously referred to P. denudata that are ecorticate and have six (5–7) pericentral cells, lateral branches that arise in the axils of trichoblasts, rhizoids cut-off from pericentral cells, trichoblasts irregularly arranged and not on every segment, spermatangial stichidia forming as a furcation of trichoblasts, and tetrasporangia arranged in straight series. Polysiphonia kapraunii sp. nov. is proposed for specimens previously referred to P. urceolata (=P. stricta) that are ecorticate and have four pericentral cells, lateral branches that replace trichoblasts, rhizoids in open connection with pericentral cells, trichoblasts irregularly arranged and not on every segment, spermatangial stichidia forming as a furcation of trichoblasts, and tetrasporangia arranged in straight series. Phylogenetic analyses of rbcL show that the newly described species are unique and clearly distinct from the species with which they had previously been identified.