Search

The brown algal genus Dictyota (Dictyotales, Phaeophyceae) is widespread, particularly in warm temperate and tropical waters, and plays a vital role in coastal ecosystems. This study reassessed the taxonomy of Dictyota, focusing on specimens from Myanmar and Japan, using a combination of morphological and molecular analyses. Molecular phylogenetic analyses using concatenated DNA sequences of rbcL, psaA, psbA, cox1 and cox3 genes revealed that Dictyota specimens from Myanmar, Japan, and other regions, belong to nine different clades, each representing a different species. Based on morphological and molecular data, seven out of these nine clades are identified as known species, while the remaining two clades are described as new species D. recumbens sp. nov. (=D. sp. A) and D. dimorphosa sp. nov. (=D. sp. B). Dictyota recumbens is characterized by the recumbent thallus, with transverse yellowish-green iridescent lines, and the formation of solitary spores irregularly distributed over the thallus. Dictyota dimorphosa is characterized by two morphological forms: decumbent and erect thalli, with bluish iridescence mainly in the decumbent thallus, and the formation of spores in oval ring shapes distributed over both thallus surfaces. Dictyota recumbens was typically found in tropical regions, while D. dimorphosa appears to be a cool-warm temperate species, distributed from northeastern Hokkaido to southern Kyushu with an extension along South Korea. Our molecular phylogenetic analyses have revealed the existence of several species whose names appeared in multiple clades, suggesting the potential for future increases in species diversity and the presence of cryptic species within certain groups. [ABSTRACT FROM AUTHOR]

Taxonomy, species diversity, and geographical distribution of the marine brown algal genus Padina (Dictyotales, Phaeophyceae) from tropical South-East Asian waters were investigated through a combination of morphological and molecular analyses. The study presents a new schematic diagram showing a suite of morphological characters including thallus hairline structures that are useful for species delineation in the genus. This study also revealed two new species from Myanmar, P. gracilis sp. nov. and P. lata sp. nov. based on molecular and morphological data. P. gracilis is characterised by a 2-layered thallus, thin hairlines on both surfaces of the thallus at equal distances, non-indusiate reproductive sori distally very close to the hairlines on the inferior surface, and the presence of Vaughaniella stage. P. lata is characterized by a 2–4-layered tiny thallus, broad hairlines located only on the inferior thallus surface, non-indusiate reproductive sori abutting the hairlines on the inferior surface and irregularly spreading on the superior surface, and the presence of Vaughaniella stage. This study also revealed new distributional records for four Padina species: P. okinawaensis from Myanmar and P. fasciata, P. ryukyuana and P. terricolor from the Philippines. These findings point to elevated species diversity in central Indo-Pacific waters. This study confirmed that most of the Padina species in the Pacific regions are showing overlapping distribution across the regions, in contrast to species from the Indian Ocean, which tend to be confined to specific localities. [ABSTRACT FROM AUTHOR]

SUMMARY The genetic diversity of freshwater Hildenbrandia species (Florideophyceae, Hildenbrandiales) from Japan was reassessed based on specimens collected from Kagoshima (Kyushu), Hyogo and Kanagawa Prefectures (Honshu), using rbcL and 18S rDNA sequences. Phylogenetic results suggested the occurrence of only one species of freshwater Hildenbrandia in Japan, H. japananensis. The clade H. jigongshanensis–H. japananensis is sister to H. rivularis. Hildenbrandia angolensis was paraphyletic and positioned basally among the freshwater Hildenbrandia clades. Furthermore, the genetic similarity between H. jigongshanensis and H. japananensis determined by rbcL and 18S sequences as well as the intraspecific morphological plasticity led us to the conclusion that the species from China and Japan were conspecific. Accordingly, we propose the taxonomic lumping of H. jigongshanensis and H. japananensis. In addition, we recommend additional molecular and morphological studies on Asian freshwater Hildenbrandia to determine whether H. jigongshanensis is conspecific with H. ramanaginae previously described from India. [ABSTRACT FROM AUTHOR]

The taxonomic status and species diversity of the brown algal genus Padina (Dictyotales, Phaeophyceae) was assessed based on DNA sequences and the morpho‐anatomy of specimens collected worldwide, especially from tropical and subtropical western Pacific regions. Phylogenetic analyses using chloroplast rbcL and mitochondrial cox3 gene sequences demonstrated four distinct clades for newly collected samples with high bootstrap support. Each species clade possesses a suite of morphological features that are not shared by any known species of Padina. These are P. imbricata sp. nov., Padina lutea sp. nov., P. moffittianoides sp. nov., and P. nitida sp. nov. The occurrence of these and other species of Padina clearly points to an elevated diversity of the genus in tropical/subtropical waters of the western Pacific. Phylogenetic analyses provided new insights into biogeographic characteristics of the genus, with many species in the Pacific Ocean showing shared/overlapping distributions, whereas species from the Mediterranean/Atlantic and/or the Indian Ocean tend to be confined to particular regions. Consideration has also been given to the evolutionary time frame of the genus Padina based on molecular time trees: a time tree of the concatenated data set (rbcL + cox3) revealed the estimated divergence time in the mid‐Cretaceous, whereas those of cox3 and rbcL showed older estimates pointing to the periods of mid‐Jurassic and Early Cretaceous, respectively. [ABSTRACT FROM AUTHOR]

The phylogeny of ligulate and sulfuric-acid containing species of Desmarestia, occurring worldwide from polar to temperate regions, was revised using a multigenic and polyphasic approach. Sequence data, gametophyte characteristics, and sporophyte morphology support reducing a total of 16 taxa to four different species. (1) D. herbacea, containing broad-bladed and highly branched forms, has dioecious gametophytes. The three other species have monoecious gametophytes: (2) D. ligulata which is profusely branched and, except for one subspecies, narrow-bladed, (3) Japanese ligulate Desmarestia, here described as D. japonica sp. nov., which is morphologically similar to D. ligulata but genetically distant from all other ligulate taxa. This species may have conserved the morphology of original ligulate Desmarestia. (4) D. dudresnayi, including unbranched or little branched broad-bladed taxa. A figure of the holotype of D. dudresnayi, which was lost for decades, was relocated. The taxonomy is complemented by a comparison of internal transcribed spacer and cytochrome c oxidase subunit I ( cox1) as potential barcode loci, with cox1 offering good resolution, reflecting species delimitations within the genus Desmarestia. [ABSTRACT FROM AUTHOR]

A study of the genus Padina in the Mediterranean Sea, based on detailed morphological and molecular analyses using chloroplast rbcL and mitochondrial cox3 gene sequences, as well as RuBisCO spacer and partial rbcS sequences, revealed the presence of two new species, P. ditristromatica Ni-Ni-Win & H. Kawai and P. pavonicoides Ni-Ni-Win & H. Kawai. They are two to three-layered and three-layered species, respectively. Padina ditristromatica is characterized by a thallus composed of two cell layers from the marginal portion to the inrolled margin and a mixture of two and three layers in the other portions; heavy calcification on both surfaces of the thallus except for the hair lines; alternating hair lines that are spaced at unequal distances between the upper and lower surfaces; and broad indusiate oogonial and tetrasporangial sori forming broken lines or patches arranged in a concentric row, which are distally close to the hair lines and half immersed in the epidermis layer only on the lower surface. Padina pavonicoides is characterized by a thallus composed of three cell layers from the base to the marginal portion and two layers at the inrolled margin; alternating hair lines that are spaced at equal distances between the upper and lower surfaces; and indusiate oogonial and tetrasporangial sori forming patches located distal to the hair lines only on the lower surface. All molecular phylogenetic analyses indicated that the new species are closely related to P. pavonica, a common species in the Mediterranean Sea. However, the cox3 region could not be amplified for P. ditristromatica. Therefore, the RuBisCO spacer and partial rbcS were analysed for the Mediterranean specimens in order to confirm their identity as well as their closest relationships. The combined rbcL, RuBisCO spacer and partial rbcS data also support their genetic separation and show that P. pavonica is more closely related to P. pavonicoides than P. ditristromatica, as in other molecular analyses. [ABSTRACT FROM AUTHOR]

Molecular phylogenetic analyses of Padina species collected from the western Pacific Ocean using rbcL and mitochondrial cox3 genes revealed the occurrence of four genetically distinctive clades of unknown Padina species: clade A (=Padina okinawaensis sp. nov.) from Ryukyu Islands (Japan), Hawaii, Indonesia and Thailand, clade B (=Padina undulata sp. nov.), clade C (=Padina terricolor sp. nov.) and clade D (=Padina fasciata sp. nov.) from Ryukyu Islands (Japan). Morphologically, these new taxa are all bistratose species, and different from any known species in the following morphological features: P. okinawaensis sp. nov., reniform or circular thallus of entire margin with inconspicuous hair lines on the superior surface of the thallus, and reproductive organs (oogonia and tetrasporangia) in small groups or discontinuous sori under thin flakes of calcium on the inferior surface; P. undulata sp. nov., circular or semicircular thallus with undulate margin, conspicuous hair lines on both surfaces of the thallus, oogonial and tetrasporangial sori in continuous or discontinuous lines covered with a persistent indusium, and cylindrical oogonia; P. terricolor sp. nov., grayish brown on the inferior surface of the thallus, and oogonial and tetrasporangial sori in continuous lines covered with a persistent indusium; P. fasciata sp. nov., broad white stripes on both surfaces of the thallus due to unique calcification, and oogonial and tetrasporangial sori in continuous lines, which are entirely embedded in a gelatinous layer, on the inferior surface of the thallus. In addition, the independence of Padina japonica from Padina sanctae-crucis is suggested on the basis of molecular and morphological evidence. [ABSTRACT FROM AUTHOR]

Three species of the brown algal genus Padina (Dictyotales), Padina melemele I.A. Abbott et Magruder, Padina moffittiana I.A. Abbott et Huisman, and Padina thivyae Doty et Newhouse, which were originally described from Hawaii, are newly reported from some of the offshore islands of Southern Japan: P. melemele collected from Okinawa (Ryukyu Islands) and Chichi-jima (Ogasawara Islands), P. moffittiana from Okinawa I. and P. thivyae from Tanega-shima. Identifications are based on morphological comparisons with the original descriptions and herbarium specimens of these species identified by I. A. Abbott. Some minor differences included tetrasporangial sori that were formed only on one surface of the thallus in Japanese P. melemele and P. thivyae, whereas in the Hawaiian specimens they were sometimes formed on both surfaces. Japanese P. moffittiana had entire margins, whereas the Hawaiian specimens generally had fimbriate margins. Molecular analyses using rbcL and mitochondrial cox3 genes as molecular markers confirmed the identification of P. melemele and P. moffittiana. Unfortunately the record of P. thivyae could not be confirmed because we were unable to extract DNA from this species. [ABSTRACT FROM AUTHOR]

A previously unknown species of kelp was collected on Kagamil Island, Aleutian Islands. The species can be easily distinguished from any known laminarialean alga: the erect sporophytic thallus is composed of a thin lanceolate blade attaining ∼2 m in height and ∼0.50 m in width, without midrib, and the edge of the blade at the transition zone is thickened to form a V-shape; the stipe is solid and flattened, slightly translucent, attaining ∼1 m in length; the holdfast is semidiscoidal and up to 0.15 m in diameter. Anatomically, the blade has the typical trumpet-shaped hyphae characteristic of the Chordaceae and derived foliose laminarialean species (i.e., Alariaceae/Laminariaceae/Lessoniaceae). No hair pits or mucilaginous structures were observed on the blade or stipe. No fertile sporophytes were collected, but abundant juvenile sporophytes were observed in the field. In the molecular phylogenetic analyses using chloroplast rbcL gene, nuclear ITS1-5.8S-ITS2 rDNA, and mitochondria nad6 DNA sequences, the new species ( Aureophycus aleuticus gen. et sp. nov.) showed a closer relationship with Alariaceae of conventional taxonomy, or the “Group 1” clade of Lane et al. (2006) including Alaria and related taxa than with other groups, although the species was not clearly included in the group. Aureophycus may be a key species in elucidating the evolution of the Alariaceae within the Laminariales. Because of the lack of information on reproductive organs and insufficient resolution of the molecular analyses, we refrain from assigning the new species to a family, but we place the new species in a new genus in the Laminariales. [ABSTRACT FROM AUTHOR]

The order Ralfsiales was established to accommodate the brown algal taxa having a crustose thallus, an isomorphic life history, discoid early development of the thallus and containing a single, plate-shaped chloroplast without pyrenoids in each cell. However, the validity of the order has been questioned by many researchers because several exceptions to these criteria have been found within the order. Molecular phylogenetic analysis of the taxa assigned to the order, using rbcL DNA sequences, reveals that Ralfsiales is not a monophyletic group but is separated into two major groups, excluding Lithodermataceae, which were not included in the present analysis: clade I, comprising the members of Ralfsiaceae, Mesosporaceae, A nalipus japonicus and Heteroralfsia saxicola; and clade II, consisting of Diplura species, sister to the Ishigeales clade. On the basis of these results, we propose emendment of the Ralfsiales to contain only species having (1) discoidal early development of the thallus; (2) intercalary plurilocular gametangia with terminal cells and terminal unilocular zoidangia; and (3) a crustose phase in the life history. Furthermore, we propose the establishment of the new family Neoralfsiaceae to accommodate the new genus Neoralfsia, on the basis of Ralfsia expansa. [ABSTRACT FROM AUTHOR]

A molecular phylogenetic analysis of the little-studied filamentous brown alga Discosporangium mesarthrocarpum (Meneghini) Hauck using rbcL and partial 18S rDNA sequences revealed that the species forms a monophyletic clade with Choristocarpus tenellus (Kütz.) Zanardini that is sister to all other brown algae. Although D. mesarthrocarpum has unique disk-shaped plurilocular reproductive organs, D. mesarthrocarpum and C. tenellus share the following basic morphological features, which are considered to be plesiomorphic characters in the brown algae: (1) apical (and diffuse) growth; (2) uniseriate, subdichotomously branched filaments; (3) multiple chloroplasts per cell without pyrenoids; and (4) lack of heterotrichy and of phaeophycean hairs. The rbcL DNA sequence of an Australian D. mesarthrocarpum specimen showed considerable deviation from Mediterranean and Macaronesian specimens. Therefore, the presence of a second species in the genus is suggested; however, the taxonomic treatment of this putative species is not pursued in the present report. Regarding the higher-ranking systematic position of D. mesarthrocarpum, reinstatement of Discosporangiaceae and Discosporangiales is proposed, and the inclusion of Choristocarpaceae in the order is also suggested. Under short-day and long-day culture conditions at 15°C–25°C, Mediterranean D. mesarthrocarpum exhibited a direct type of life history, with a succession of uniseriate filamentous thalli bearing characteristic disk-shaped plurilocular zoidangia, but thalli did not survive at 10°C and below. [ABSTRACT FROM AUTHOR]

gene have been reported to date. Four new cases from Caulerpales, Ulvophyceae are described here. In the genus Caulerpa, the presence of an intron was unstable even in the infraspecific taxa. Based on comprehensive comparisons of the inserted positions, lengths of introns and so on, the presence of at least three kinds of introns, which probably have independent origins, was suggested in Caulerpales. [ABSTRACT FROM AUTHOR]