Zhongmin Sun

Taxonomic revision of the genus Lobophora (Dictyotales, Phaeophyceae) based on morphological evidence and analyses rbcL and cox3 gene sequences

Sun Z., Hanyuda T., Lim P.E., Tanaka J., Gurgel C.F.D. and Kawai H. 2012. Taxonomic revision of the genus Lobophora (Dictyotales, Phaeophyceae) based on morphological evidence and analyses rbcL and cox3 gene sequences. Phycologia 51: 500–512. DOI: 10.2216/11-85.1 A taxonomic revision of Lobophora based on molecular phylogenetic analyses of rbcL and cox3 gene sequences as well as anatomical observations was carried out, mostly based on specimens collected from eastern Asia and southeastern Australia. In the molecular phylogenetic analyses, nine major clades supported by high bootstrap values were recognized. In combination with evaluation of morphological characters, four clades were concluded to be new species. The Australian species L. australis sp. nov. possessed erect thalli with sporangial sori scattered on the ventral surface and had a closer phylogenetic relationship with another Australian species, L. nigrescens, but it was distinguished from the latter in having fewer layers of cortical cells and smaller sporangia. The Asian species L. crassa sp. nov., L. pachyventera sp. nov. and L. asiatica sp. nov. possessed decumbent thalli with sporangia scattered on the dorsal surface. Among the three prostrate species, L. crassa had a considerably thicker thallus with four to five cortical layers, L. asiatica had a thinner thallus with two cortical layers, and L. pachyventera differed from another two species by its three-layered ventral cortex and well-developed anchoring rhizoids.

Phylogeographic structure and deep lineage diversification of the red alga Chondrus ocellatus Holmes in the Northwest Pacific.

A major goal of phylogeographic analysis using molecular markers is to understand the ecological and historical variables that influence genetic diversity within a species. Here, we used sequences of the mitochondrial Cox1 gene and nuclear internal transcribed spacer to reconstruct its phylogeography and demographic history of the intertidal red seaweed Chondrus ocellatus over most of its geographical range in the Northwest Pacific. We found three deeply separated lineages A, B and C, which diverged from one another in the early Pliocene–late Miocene (c. 4.5–7.7 Ma). The remarkably deep divergences, both within and between lineages, appear to have resulted from ancient isolations, accelerated by random drift and limited genetic exchange between regions. The disjunct distributions of lineages A and C along the coasts of Japan may reflect divergence during isolation in scattered refugia. The distribution of lineage B, from the South China Sea to the Korean Peninsula, appears to reflect postglacial recolonizations of coastal habitats. These three lineages do not coincide with the three documented morphological formae in C. ocellatus, suggesting that additional cryptic species may exist in this taxon. Our study illustrates the interaction of environmental variability and demographic processes in producing lineage diversification in an intertidal seaweed and highlights the importance of phylogeographic approaches for discovering cryptic marine biodiversity.

Effects of salinity and nutrients on the growth and chlorophyll fluorescence of Caulerpa lentillifera

Caulerpa lentillifera is a green algae that distributes worldwide and is cultivated for food. We assessed vegetative propagation of C. lentillifera by measuring the specific growth rate (SGR) and chlorophyll fluorescence of the green algae cultured at different salinities and nutrient levels. The results indicated that C. lentillifera can survive in salinities ranging from 20 to 50, and can develop at salinities of 30 to 40. The maximum SGR for C. lentillifera occurred at a salinity of 35. Both chlorophyll content and the ratio of variable to maximum fluorescence (Fv/Fm) were also at a maximum at a salinity of 35. Photosynthesis was inhibited in salinities greater than 45 and less than 25. Both the maximum SGR and maximum chlorophyll content were found in algae treated with a concentration of 0.5 mmol/L of NO3-N and 0.1 mmol/L of PO4-P. The photosynthetic capacity of photosystem II (PSII) was inhibited in cultures of C. lentillifera at high nutrient levels. This occurred when NO3-N concentrations were greater than 1.0 mmol/L and when PO4-P concentrations were at 0.4 mmol/L. As there is strong need for large-scale cultivation of C. lentillifera, these data contribute important information to ensure optimal results.

Diterpenes from a Chinese Collection of the Brown Alga Dictyota plectens

Twenty-seven diterpenes of six chemical classes, including seven new diterpenes (1, 2, 6, 10, 11, 16, and 19), have been isolated from a collection of the brown alga Dictyota plectens from the South China Sea. The structures of the new diterpenes were elucidated by extensive spectroscopic analysis and by comparison with reported data. In the in vitro assays, 9, 12, 14, 16, and 22 showed inhibitory activity against HIV-1 replication with IC50 values of 16.1-30.5 μM, compounds 5, 13, 24, and 26 exhibited anti-H5N1 activity with inhibition rates of 50%-62% at 30.0 μM, and 12 and 24 also showed potent inhibition against LPS-induced NO production with inhibition rates of 90% and 86%, respectively, at 10.0 μM.

Hidden diversity and phylogeographic history provide conservation insights for the edible seaweed Sargassum fusiforme in the Northwest Pacific

Understanding the evolutionary processes that have created diversity and the genetic potential of species to adapt to environmental change is an important premise for biodiversity conservation. Herein, we used mitochondrial trnW‐L and cox3 and plastid rbcL‐S data sets to analyze population genetic variation and phylogeographic history of the brown alga Sargassum fusiforme, whose natural resource has been largely exterminated in the Asia–Northwest Pacific in the past decades. Phylogenetic trees and network analysis consistently revealed three major haplotype groups (A, B, and C) in S. fusiforme, with A and B distributed in the Japan‐Pacific coast. Group C consisted of three subgroups (C1, C2, and C3) which were distributed in the Sea of Japan, the Yellow–Bohai Sea, and East China Sea, respectively. Isolation‐with‐migration (IMa) analysis revealed that the three groups diverged approximately during the mid‐Pleistocene (c. 756–1,224 ka). Extended Bayesian skyline plots (EBSP) showed that groups A and B underwent relatively long‐term stable population size despite a subsequent rapid demographic expansion, while subgroups C2 and C3 underwent a sudden expansion at c. 260 ka. FST and AMOVA detected low population‐level genetic variation and high degrees of divergence between groups. The cryptic diversity and phylogeographic patterns found in S. fusiforme not only are essential to understand how environmental shifts and evolutionary processes shaped diversity and distribution of coastal seaweeds but also provide additional insights for conserving and managing seaweed resources and facilitate predictions of their responses to future climate change and habitat loss.

Further New Xenicanes from a Chinese Collection of the Brown Alga Dictyota plectens

Four new xenicanes, namely 4α-hydroxyisodictyohemiacetal (1), 4α-hydroxyisodictyoacetal (2), 13,18-diacetoxy-4-hydroxyisodictyo-19-al (3), and 4α-hydroxypachylactone (8), were isolated from a Chinese collection of the brown alga Dictyota plectens, along with four known analogues (4-7). The structures of the new diterpenes were determined by extensive spectroscopic data analysis. All compounds were evaluated for their antiviral activities against human immunodeficiency virus type 1 (HIV-1) and the highly pathogenic avian influenza A (H5N1) virus, and inhibitory effects on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in mouse peritoneal macrophages (PEMΦ).

Genetic and morphological analyses of Gracilaria firma and G. changii (Gracilariaceae, Rhodophyta), the commercially important agarophytes in western Pacific

Many studies classifying Gracilaria species for the exploitation of agarophytes and the development of the agar industry were conducted before the prevalence of molecular tools, resulting in the description of many species based solely on their morphology. Gracilaria firma and G. changii are among the commercially important agarophytes from the western Pacific; both feature branches with basal constrictions that taper toward acute apices. In this study, we contrasted the morpho-anatomical circumscriptions of the two traditionally described species with molecular data from samples that included representatives of G. changii collected from its type locality. Concerted molecular analyses using the rbcL and cox1 gene sequences, coupled with morphological observations of the collections from the western Pacific, revealed no inherent differences to support the treatment of the two entities as distinct taxa. We propose merging G. changii (a later synonym) into G. firma and recognize G. firma based on thallus branches with abrupt basal constrictions that gradually taper toward acute (or sometimes broken) apices, cystocarps consisting of small gonimoblast cells and inconspicuous multinucleate tubular nutritive cells issuing from gonimoblasts extending into the inner pericarp at the cystocarp floor, as well as deep spermatangial conceptacles of the verrucosa-type. The validation of specimens under different names as a single genetic species is useful to allow communication and knowledge transfer among groups from different fields. This study also revealed considerably low number of haplotypes and nucleotide diversity with apparent phylogeographic patterns for G. firma in the region. Populations from the Philippines and Taiwan were divergent from each other as well as from the populations from Malaysia, Thailand, Singapore and Vietnam. Establishment of baseline data on the genetic diversity of this commercially important agarophyte is relevant in the context of cultivation, as limited genetic diversity may jeopardize the potential for its genetic improvement over time.

Historical biogeography of the highly diverse brown seaweed Lobophora (Dictyotales, Phaeophyceae)

The tropical to warm-temperate marine brown macroalgal genus Lobophora (Dictyotales, Phaeophyceae) recently drew attention because of its striking regional diversity. In this study we reassess Lobophora global species diversity, and species distributions, and explore how historical factors have shaped current diversity patterns. We applied a series of algorithmic species delineation techniques on a global mitochondrial cox3 dataset of 598 specimens, resulting in an estimation of 98-121 species. This diversity by far exceeds traditional diversity estimates based on morphological data. A multi-locus time-calibrated species phylogeny using a relaxed molecular clock, along with DNA-confirmed species distribution data was used to analyse ancestral area distributions, dispersal-vicariance-founder events, and temporal patterns of diversification under different biogeographical models. The origin of Lobophora was estimated in the Upper Cretaceous (-75 to -60 MY), followed by gradual diversification until present. While most speciation events were inferred within marine realms, founder events also played a non-negligible role in Lobophora diversification. The Central Indo-Pacific showed the highest species diversity as a result of higher speciation events in this region. Most Lobophora species have small ranges limited to marine realms. Lobophora probably originated in the Tethys Sea and dispersed repeatedly in the Atlantic (including the Gulf of Mexico) and Pacific Oceans. The formation of the major historical marine barriers (Terminal Tethyan event, Isthmus of Panama, Benguela upwelling) did not act as important vicariance events. Long-distance dispersal presumably represented an important mode of speciation over evolutionary time-scales. The limited geographical ranges of most Lobophora species, however, vouch for the rarity of such events.

Polysaccharides and their depolymerized fragments from Costaria costata: Molecular weight and sulfation-dependent anticoagulant and FGF/FGFR signal activating activities

Crude polysaccharides from Costaria costata were extracted by hot water and further fractionated by anion exchange chromatography into three polysaccharide fractions. Three low molecular weight fragments were then prepared by degradation of the polysaccharides with hydrogen peroxide and ascorbic acid. The structural features of the polysaccharides and their low molecular weight fragments were elucidated for the first time based on the HGPC, FT-IR, NMR, MS, monosaccharide composition, and other chemical analyses. Their anticoagulant and FGF-1, -2, -7, -8, -9, -10/FGFR1c signaling activation activities in BaF3 cells were also examined. Our studies showed that the polysaccharides were sulfated at different positions of galactose and fucose residues. The APTT-, PT- and TT-based anticoagulant assay results indicated that a high molecular weight and a higher degree of sulfation were essential for their anticoagulant activities. In contrast, not only the polysaccharides but also the depolymerized fragments showed significant FGF/FGFR signal activating activities in a FGF-, molecular weight-, and sulfation-dependent manner. The results presented in current study demonstrated the potential use of the polysaccharides and their fragments as anticoagulants and FGF signal regulators.

Taxonomy and molecular phylogeny of three marine benthic species of Haslea (Bacillariophyceae), with transfer of two species to Navicula

Using light, scanning and transmission electron microscopy, and SSU rDNA and rbcL gene sequencing, we investigated three marine benthic diatoms: Haslea avium Tiffany, Herwig et Sterrenburg; H. feriarum Tiffany et Sterrenburg and H. tsukamotoi Sterrenburg et Hinz collected from intertidal sediments in China. These are the first records of these three species from China. Our observations showed that the typical valve structure of Haslea, with an inner basal layer and an outer tegumental layer, and walls (saepes sensu Sterrenburg et al.) between them is not present in either H. tsukamotoi or H. avium. Moreover, the two species possess small helictoglossae, an internal apical thickened area and hooked terminal fissures reaching to the valve mantle, suggesting a close relationship with Navicula tripunctata, the type species of Navicula s.s. In molecular phylogenetic analyses, Haslea was polyphyletic, being divided into two separate clades: H. feriarum belonged to a clade that comprised only Haslea species, including the type H. ostrearia, while H. tsukamotoi and H. avium were within the Navicula clade. Therefore, we propose transferring H. tsukamotoi and H. avium to Navicula and suggest that the presence of continuous longitudinal strips on the external valve surface is not a synapomorphy, but rather a homoplastic character for Haslea.