Fucales (Phaeophyceae) from Spain characterized by large-scale discontinuous nuclear DNA contents consistent with ancestral cryptopolyploidy

Abstract

Gómez Garreta A., Ribera Siguan M.A., Salvador Soler N., Rull Lluch J. and Kapraun D.F. 2010. Fucales (Phaeophyceae) from Spain characterized by large-scale discontinuous nuclear DNA contents consistent with ancestral cryptopolyploidy. Phycologia 49: 64–72. DOI: 10.2216/09-14.1

The DNA-localizing fluorochrome 4′,6-diamidino-2-phenylindole and chicken erythrocytes standard were used with image analysis and static microspectrophotometry to estimate nuclear DNA contents (I_f) in 19 species and varieties of Fucales from the Atlantic and Mediterranean coasts of Spain. Negligible differences were found between specimens fixed in Carnoy's solution (EtOH) and methanol-Carnoy's (methacarn). Present and previously published nuclear DNA content estimates expand our database to include 23 species and varieties representing nine genera with a 2C range of 0.4–0.8 pg in Sargassaceae and 1.1–2.2 pg in Fucaceae and Himanthaliaceae, excluding polyploid isolates. Intraplant variation was observed in most isolates and 8C nuclei were quantified in seven taxa and isolates. In 11 taxa, I_f levels in 2C male gamete nuclei were found to closely approximate 50% of 4C values in vegetative cells of mature plants, consistent with meiosis and a sexual life history in these haplobiontic algae. Availability of consensus higher-level phylogenetic trees for Fucales has opened the way for determining evolutionary trends in DNA amounts. The largest genome sizes were observed in cold-water species of Fucaceae. Both estimated genome sizes and published chromosome numbers for Fucales suggest a large-scale, discontinuous distribution of discrete values that can be explained in terms of ancestral cryptopolyploidy events.

Key Words::

• DNA C-values
• Fucales
• Nuclear genome size
• Phaeophyceae

ACKNOWLEDGMENTS

We are grateful to Ignacio Barbara, Coro Casares and Angela Noguerol for providing material from the Atlantic, Marius Mumbrú for his technical support in the laboratory, Raquel García for her assistance in the image analysis and Joan Vallès for his comments. This study was supported by project CGL2005-02330/BOS of the Spanish Government.