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: 10.2216/07-99.1

The 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.

Key Words::

• Atlantic Ocean
• Azores
• Life history
• Nemastomatales
• Platoma
• rbcL
• Rhodophyta
• Schizymeniaceae

ACKNOWLEDGMENTS

DG thanks the Fundação para a Ciência e Tecologia (FCT) for her PhD grant SFRH/BD/12541/2003 and Centro de Investigação de Recursos Naturais da Universidade dos Açores (CIRN/UA, FCT) for providing logistic facilities for the development of the work and travel grants. The National Science Foundation Biodiversity Surveys and Inventories grant DEB 0315995 made it possible to gain a better understanding of seaweed diversity throughout the Gulf of Mexico, and DEB 0743024 and OISE 0819205 to do research on taxa from Panama. We also thank Boo Yeon Won, Brigitte Gavio, Constanza Ehrenhaus, David Krayesky, Frederico Gurgel, João Brum, Natalia Arakaki, Nuno Álvaro, Patrícia Madeira, Sandra Monteiro, Tae Oh Cho, William Schmidt and the R/V Pelican crew for their help in collecting, and Ian Tittley (Herbarium MNHN, London) and Olivier de Clerk and Eric Coppejans (Herbarium Ghent) for providing herbarium samples.