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A NEW BROWN ALGAL ORDER, ISHIGEALES (PHAEOPHYCEAE), ESTABLISHED ON THE BASIS OF PLASTID PROTEIN‐CODING rbc L, psa A, AND psb A REGION COMPARISONS 1
Author(s) -
Cho Ga Youn,
Lee Sang Hee,
Boo Sung Min
Publication year - 2004
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.1529-8817.2004.03160.x
Subject(s) - biology , pyrenoid , plastid , sporangium , brown algae , botany , phylogenetics , chloroplast , lineage (genetic) , algae , ultrastructure , evolutionary biology , gene , genetics , spore
The brown algal family Ishigeaceae currently includes a single genus, Ishige Yendo, with two species. The relationship of the family to other brown algal lineages is less studied in terms of their plastid ultrastructure and molecular phylogeny. We determined the sequences of rbc L from four samples of the two Ishige species and nine putative relatives and the psa A and psb A sequences from 37 representatives of the brown algae. Analyses of individual and combined data sets resulted in similar trees; however, the concatenated data gave greater resolution and clade support than each individual gene. In all the phylogenies, the Phaeophyceae was well resolved, the Ectocarpales being placed in a terminal position and the Ishigeaceae ending up in a basal position. From our ultrastructural study, we concluded that the pyrenoid is absent in the Ishigeaceae, despite the presence of a rudimentary pyrenoid in I. okamurae . These results suggest that the Ishigeaceae is an early diverging brown lineage. Our molecular and morphological data, therefore, lead us to exclude the Ishigeaceae from the Ectocarpales s.l ., which have an elaborate pyrenoid, and to propose its own order Ishigeales ord. nov. The Ishigeales is distinguished by oligostichous structure of thalli, phaeophycean hairs formed within cryptostomata, unilocular sporangia transformed from terminal cortical cells, and plurilocular sporangia lacking sterile terminal cells. This study is the first to document the utility of the psa A and psb A sequences for brown algae and also the first report on the multigene phylogeny of the Phaeophyceae based on three protein‐coding plastid genes.