Phylogenetic appraisal of the genus Platoma (Nemastomatales, Rhodophyta), including life history and morphological observations on P. cyclocolpum from the Azores

Abstract

Gabriel D., Parente M.I., Neto A.I., Raposo M., Schils T. and Fredericq S. 2010. Phylogenetic appraisal of the genus Platoma (Nemastomatales, Rhodophyta), including life history and morphological observations on P. cyclocolpum from the Azores. Phycologia 49: 2–21. DOI: 10.2216/07-99.1The red algal genus Platoma Schmitz (Schizymeniaceae, Nemastomatales) with type Platoma cyclocolpum (Montagne) Schmitz was originally described from the Canary Islands. Life history studies were conducted on P. cyclocolpum from the Azores under 10°C/8∶16 light (L)∶dark (D), 15°C/16∶8 L∶D, and 23°C/natural daylight regimes in culture. Three nonreproductive modes of thallus development resulted from germinating carpospores: (1) a permanent crust, (2) a filiform, nonfoliose erect thallus occasionally attached by a holdfast composed of cell aggregations, and (3) a filiform, nonfoliose erect thallus has been reported previously for populations from the Canary Islands, but the latter two have not been described before. Platoma cyclocolpum is widely reported in the literature, but specimens under that name from Madagascar are identified here as Platoma chrysymenioides Gavio et al., a deepwater species first described from the northern Gulf of Mexico and now recorded for the entire gulf. Genuine P. cyclocolpum specimens from the Azores, Madeira, and the Canary Islands were sequenced for chloroplast-encoded rbcL, and phylogenetic relationships of four Platoma species are discussed. A table listing diagnostic morphological and anatomical features of Platoma species is provided.