• ALGAE
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• v.20 no.2
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• pp.91-97
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• 2005

The brown algal family Chordariaceae sensu lato is a focus of taxonomy because recent studies suggest a broad concept of the family, including genera formerly classified in the Dictyosiphonales. Using morphology, plastid rbcL and nrDNA ITS sequences, we evaluated relationships of the monotyic genus Soranthera (S. ulvoidea), which has been classified in the Punctariaceae. The species occurs in Bering Sea and Aleutian Islands, Alaska to Baja California. Thalli are globose to lobed, hollow, 3-5 cm in diameter, and covered with evenly distributed sori. However, two forms within the species are recognized: f. ulvoidea for globose forms and f. difformis for lobed forms. Plastid rbcL and nuclear ITS region sequences were newly determined in samples of S. ulvoidea from the Pacific coast of the North America. We found little variations in the ITS sequences among samples of S. ulvoidea from five different locations and in the rbcL region from two different locations. These results do not support previous classification of f. ulvoidea and f. difformis within the species. All analyses of our rbcL sequence dataset show that Soranthera was placed in the Chordariaceae s.l., but more related to Botrytella than Punctaria and Asperococcus.