• ALGAE
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• v.29 no.4
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• pp.289-297
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• 2014

The taxonomic status and the distribution of Rosenvingea species need attention because of the difficulties in morphological identification in the laboratory as well as in the field. We analyzed mitochondrial cox3 and plastid psaA gene sequences from Rosenvingea species from Vietnam, Mexico and Panama in combination with morphological examinations. Our results confirmed the occurrence of R. intricata and R. orientalis in Vietnam. R. intricata formed dense decumbent mats with many flat branches, often inter-adhesive, and was up to 5 cm in diameter. R. orientalis thalli were up to 18 cm long with narrow (less than 2 mm in width) tubular to compressed fronds. Both cox3 and psaA phylogenies revealed the non-monophyly of the genus Rosenvingea, as reported previously for other scytosiphonacean genera.

• ALGAE
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• v.25 no.4
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• pp.187-195
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• 2010

The genus Rosenvingea is well known in the tropics. Four species have been reported from Pacific Mexico: R. floridana, R. antillarum, R. intricata and R. sanctae-crucis. We collected a plant (Boca del Cielo, Chiapas) that we identified as Rosenvingea orientalis, a species not previously reported from Pacific Mexico. We were able to characterize the life cycle of this species for the first time in laboratory culture. It reproduced exclusively by plurilocular sporangia (plurangia). The mature plants were up to 6 cm long with cylindrical to compressed fronds (to 2 mm wide) with dichotomous branches in the upper half of the thallus. The medulla was hollow with 2-3 layers of large inflated colourless cells at the periphery. The cortex was comprised of 1 layer of small cells, each with a single chloroplast and pyrenoid. Linear plurangial sori with phaeophycean hairs formed along the mature fronds. Zoospore germlings developed into prostrate filamentous systems, each with a single phaeophycean hair that gave rise to a single erect shoot with multiple hairs arising near the tip. Molecular phylogeny using the psaA gene placed this isolate within the Scytosiphonaceae. It does not confirm the exact identification of R. orientalis, although its placement close to other Rosenvingea sequences was confirmed and morphological evidence supports its placement in R. orientalis. Our culture investigations indicated that it has an asexual life cycle. Further collections are needed to resolve the full generic and specific relationships of Rosenvingea and related taxa, and their reproductive patterns.

• ALGAE
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• v.21 no.2
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• pp.175-183
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• 2006

Recent phylogenetic studies of scytosiphonacean brown algae show many conflicts with current classification. In order to clearly define the phylogenetic relationships of the family, we newly sequenced the photosystem I coding psaA gene (1488 base pairs) from 13 taxa (15 samples), of the family, and, for comparison, rbcL from four taxa. The psaA region has more informative sites (17.9%) than the rbcL (13.1%) and the number of nodes supported by over 50% bootstrap values is more in the psaA phylogeny (53 /57 nodes; 93%) than in the rbcL (47/63 nodes; 74.6%). The psaA phylogenies are basically congruent with the rbcL trees, recognizing two major groups in the monophyletic Scytosiphonaceae. The first group included Myelophycus, Petalonia, Scytosiphon, and elongate sack-shaped species of Colpomenia, primarily cold temperate elements with unilocular zoidangia on sporophytes. The second group, although not resolved, consisted of Hydroclathrus, Chnoospora, Rosenvingea, and ball-shaped Colpomenia, primarily warm-temperate taxa with both unilocular and plurilocular zoidangia on sporophytes. Chnoospora is not monophyletic, as was previously shown the paraphyly of Colpomenia, Petalonia, and Scytosiphon. Hydroclathrus clathratus from Korea and Japan was not monophyletic. Our studies show that gametophytic characters are the main source of conflict for the present taxonomy of the family. The psaA region is a useful tool for resolution of phylogenetic relationships within the Scytosiphonaceae.