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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]

SUMMARY: The subtidal brown algal species Sporochnus dotyi Brostoff (Sporochnales, Phaeophyceae), which has been regarded as a Hawaiian endemic, is reported from Kushimoto, Kii Peninsula, Pacific coast of central Honshu, Japan, for the first time outside Hawai'i. The species grew on subtidal rocks ca. 5–20 m deep attached by a small conical holdfast. The erect thalli were 5–30 cm high, terete, robust and alternately branched in 1–2 orders. When mature, pedicellate receptacles developed on the branches, and formed elliptical sori 1 mm long with a pedicel 3–5 mm long. The apical parts of the thalli and the receptacles were terminated with a tuft of simple assimilatory filaments of up to 4 mm long and showed prominent green to yellow underwater iridescence. Reproductive filaments (paraphyses) were densely packed, simple, up to 200 μm long and bore 4–6 mostly unilateral unilocular zoidangia 20–22 μm long and 5–6 m in diameter. In the genetic analyses, the Sporochnus alga from Kushimoto had partial rbcL sequence identical to S. dotyi from Hawai'i. The cox3 phylogeny revealed that this alga formed a fully supported clade with S. dotyi. Therefore, we identified the alga from Kushimoto as S. dotyi. This finding of S. dotyi from Japan, together with the recent reports of the mesophotic macroalgae Ryuguphycus kuaweuweu (=Umbraulva kuaweuweu), Ulva iliohaha and Newhousia imbricata from various localities in the Pacific Ocean including Japan, suggest closer biogeographical connections of subtidal/mesophotic macroalgae in the Pacific than previously recognized. [ABSTRACT FROM AUTHOR]

Molecular phylogeny based on concatenated sequences of chloroplast atpB, psaA, psbA, psbC and rbcL genes indicates that the filamentous brown alga Pilinia rimosa is phylogenetically distant from the Ectocarpales, in which it has been classified (as Waerniella lucifuga). In the tree, Pilinia was sister to the clade comprised of Ishige and Petroderma (Ishigeales) supported by high statistical values. Observations of unialgal P. rimosa cultures originating from Helgoland (Germany), England (UK), Woods Hole (USA) and Newfoundland (Canada) showed a direct type of life history with reproduction by characteristic unilocular zoidangia typically forming only four zoids. Despite the description of plurilocular zoidangia in Kuckuck's account as well as in later publications, we conclude that those observations were based on misinterpretation of the very small unilocular zoidangia formed in series, often with longitudinal walls between zoidangia. Pilinia rimosa grows in caves or crevices in rocks, and on walls or wood pilings in deep shade in the upper intertidal and spray zone, and is therefore regarded as a marine species, but it could also survive and mature in freshwater medium. We propose the establishment of a new family Piliniaceae for Pilinia and place it in Ishigeales. Molecular and morphological analysis of the culture strains, SAG 124.79 and SAG 2381, identified as the euryhaline alga Porterinema fluviatile, indicated that SAG 124.79 is in fact P. rimosa. However, SAG 2381 is true P. fluviatile, also displaying the characteristic plurilocular zoidangia. Porterinema was shown to be a member of the Chordariaceae, Ectocarpales sensu lato. [ABSTRACT FROM AUTHOR]

Dictyosiphon asiaticus sp. nov. and D. sparsus sp. nov. are newly described from Japan and the north-western Pacific. Molecular phylogenies based on the mitochondrial cox1 and cox3 and chloroplast atpB, psaA, psbA and rbcL DNA sequences revealed that Dictyosiphon comprises at least seven lineages worldwide. Japanese Dicytosiphon species formed two clades with high support and were sister to a clade including specimens from the cold-water regions of the northern Pacific, the Arctic, and the north-western Atlantic. Specimens of one of the Japanese clades (= D. asiaticus sp. nov.) were morphologically similar to D. foeniculaceus (generitype described from Scotland, UK), having densely branched thalli with fine branches, and were epiphytic on Scytosiphon spp. and Chordaria spp. Specimens of the other Japanese clade (= D. sparsus sp. nov.) were morphologically similar to D. chordaria, having somewhat thicker, sparse branches with blunt tips, and were epiphytic on Chordaria spp. We assign the third clade distributed on both sides of the North Pacific to D. sinicola, which was described from Washington, USA, for the following reasons: Dictyosiphon specimens in the region having relatively densely branched thalli with fine tips have been identified as D. foeniculaceus, and D. sinicola was distinguished from them by its remarkably larger thallus, while anatomically they are very similar. However, D. foeniculaceus is not widely distributed in the region, with only one genetic lineage (species) reported, so that those two taxa are considered to be ecotypes of the same species, and D. sinicola is the valid name for the taxon. [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]

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]

Reports of naturally occurring hybridization between species and genera in Laminariales are limited. Hybrids are mostly identified based on morphological evidence, which is often inadequate to distinguish hybrids from other unusual kelp morphological variants. In the present study, we found morphologically atypical Ecklonia (Ec.), which were suspected of being hybrids between Ec. radicosa (Ecr) and Ec. cava subsp. stolonifera (Eccs) (IKI 09–23) or between Ecr and Eisenia (Ei.) nipponica (Ein) (OWS 07–13), in two localities in Japan. To verify the existence of naturally occurring hybrids in Ec., we determined their maternal ancestry by mtDNA genotyping and assigned the putative hybrids to four categories (F1, F2 and backcross to parental species) based on microsatellite markers. The morphologically atypical specimens were defined as: F1 generation of Ecr ♂ × Eccs ♀ (IKI 12, IKI 15–17 and IKI 19–22), Ecr ♀ × Eccs ♂ (IKI 11), or Ecr ♂ × Ein ♀ (OWS 07 and OWS 10–13), with relatively high posterior probabilities (>0.700). The remaining specimens were non-hybrids (Eccs: IKI 09, IKI 10 and IKI 13; Ecr: IKI 18), F1 or backcrosses to Ecr (IKI 14, IKI 23 and OWS 08) and F1, F2 or backcrosses to Ecr (OWS 09). Our results provide strong genetic evidence for the existence of intra- and inter-generic hybrids of Ecklonia in the field. [ABSTRACT FROM AUTHOR]

The reproductive structures, early development and carotenoid composition of Umbraulva kuaweuweu, which is a deep-water ulvacean species recently reported from Hawaii, are reported for the first time using the specimens collected by dredging at ~30 m depth from Ogasawara Islands and Mageshima in southern Japan. Although Umbraulva kuaweuweu had siphonaxanthin as in U. japonica, a characteristic carotenoid of Umbraulva, U. kuaweuweu lacked α-carotene and β-carotene. U. kuaweuweu differed markedly from U. japonica in thallus morphology and reproductive structures: cell shape, presence/absence of inner rhizoidal filaments in the upper parts of thalli, solid/partly saccate thalli, and developmental processes of zoids. Multigene concatenated DNA sequences of chloroplast rbcL and tufA genes, and nuclear 18S, 5.8S, 28S rDNA and rDNA ITS1 and ITS2 regions indicated separation of U. kuaweuweu from the clade comprised of the generitype U. japonica, U. amamiensis, U. dangeardii and U. kaloakulau. In conclusion, based on the distinctive morphology, life history, carotenoid composition and molecular phylogeny, we propose the establishment of a new genus Ryuguphycus gen. nov. to accommodate U. kuaweuweu, as R. kuaweuweu comb. nov. [ABSTRACT FROM AUTHOR]