title: Taxonomic revision of the Agaraceae with a description of Neoagarum gen. nov. and reinstatement of Thalassiophyllum.
abstract: We confirmed the monophyly of the Agaraceae based on phylogenetic analyses of six mitochondrial and six chloroplast gene sequences from Agarum, Costaria, Dictyoneurum, and Thalassiophyllum species, as well as representative species from other laminarialean families. However, the genus Agarum was paraphyletic, comprising two independent clades, A. clathratum/A. turneri and A. fimbriatum/A. oharaense. The latter clade was genetically most closely related to Dictyoneurum spp., and morphologically, the species shared a flattened stipe bearing fimbriae (potential secondary haptera) in the mid- to upper portion. The phylogenetic position of Thalassiophyllum differed between the two datasets: in the chloroplast gene phylogeny, Thalassiophyllum was included in the A. clathratum/A. turneri clade, but in the mitochondrial gene phylogeny, it formed an independent clade at the base of the Agaraceae, the same position it took in the phylogeny when the data from both genomes were combined despite a larger number of bp being contributed by the chloroplast gene sequences. Considering the remarkable morphological differences between Thalassiophyllum and other Agaraceae, and the molecular support, we conclude that Thalassiophyllum should be reinstated as an independent genus. Dictyoneurum reticulatum was morphologically distinguishable from D. californicum due to its midrib, but because of their close genetic relationship, further investigations are needed to clarify species-level taxonomy. In summary, we propose the establishment of a new genus Neoagarum to accommodate A. fimbriatum and A. oharanese and the reinstatement of the genus Thalassiophyllum.
authors.affiliation: Kobe University Research Center for Inland Seas, 1-1 Rokkodai, Kobe, 657-8501, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kawai
authors.affiliation: Kobe University Research Center for Inland Seas, 1-1 Rokkodai, Kobe, 657-8501, Japan.
authors.forename: Takeaki
authors.initials: T
authors.lastname: Hanyuda
authors.affiliation: Kobe University Research Center for Inland Seas, 1-1 Rokkodai, Kobe, 657-8501, Japan.
authors.forename: Xu
authors.initials: X
authors.lastname: Gao
authors.affiliation: Kobe University Research Center for Inland Seas, 1-1 Rokkodai, Kobe, 657-8501, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Terauchi
authors.affiliation: Natural History Museum & Institute, Chiba 955-2 Aobacho, Chiba, 260-8662, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Miyata
authors.affiliation: Department of Botany & Beaty Biodiversity Museum, University of British Columbia, #3529-6270 University Blvd., Vancouver, BC, Canada, V6T 1Z4.
authors.forename: Sandra C
authors.initials: SC
authors.lastname: Lindstrom
authors.affiliation: Kamchatka State Technical University, Klyuchevskaya Str. -3, 683003, Petropavlovsk-Kamchatsky, Russia.
authors.forename: Nina G
authors.initials: NG
authors.lastname: Klochkova
authors.affiliation: Silva Center for Phycological Documentation, University Herbarium, University of California, 1001 Valley Life Sciences Building #2465, Berkeley, California, 94720, USA.
authors.forename: Kathy Ann
authors.initials: KA
authors.lastname: Miller
mesh_terms: D061125:Genes, Chloroplast / Q000235:genetics; D050259:Genes, Mitochondrial / Q000235:genetics; D000459:Phaeophyceae / Q000145:classification / Q000235:genetics*; D010802:Phylogeny
keywords: Agaraceae; Laminariales; Neoagarum gen. nov.; molecular phylogeny; taxonomy