Consistency of morphological characters used to delimit Polysiphonia sensu lato species (Ceramiales, Florideophyceae): analyses of North Carolina, USA specimens

Polysiphonia senses lato (including Ncosiphonia) is a genus within the red algal order Ceramiales that includes over 200 current species and is distributed throughout the world. The consistency of morphological characters commonly used to distinguish species was tested by analyses of these characters within eight North Carolina, USA, species of P. sensu lato objectively defined by rbcL sequence analysis. Examination of 22 characters found five to be consistent and useful for identifying species: number of pericentral cells, rhizoid-pericentral cell connection, relationship of lateral branches to trichoblasts, spermatangial axes development, and arrangement of tetrasporangia. Character states for the pattern and occurrence of trichoblasts and scar cells, the type of the holdfast, and formation of cicatrigenous branches may also help to strengthen the distinctions among species; although, some of these characters were not uniformly consistent. These morphological findings may be applicable to the study of P. senses lato from other regions as well. The eight North Carolina species were resolved in a variety of positions within the Polysiphonia sensu lato rbcL tree, and integrated molecular and morphological analyses indicated that two, Polysiphonia denudata and Polysiphonia urceolata, have been historically misidentified.