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We investigated species diversity and distribution patterns of the marine red alga Portieria in the Philippine archipelago. Species boundaries were tested based on mitochondrial, plastid and nuclear encoded loci, using a general mixed Yule-coalescent (GMYC) model-based approach and a Bayesian multilocus species delimitation method. The outcome of the GMYC analysis of the mitochondrial encoded cox2-3 dataset was highly congruent with the multilocus analysis. In stark contrast with the current morphology-based assumption that the genus includes a single, widely distributed species in the Indo-West Pacific (Portieria hornemannii), DNA-based species delimitation resulted in the recognition of 21 species within the Philippines. Species distributions were found to be highly structured with most species restricted to island groups within the archipelago. These extremely narrow species ranges and high levels of intra-archipelagic endemism contrast with the wide-held belief that marine organisms generally have large geographical ranges and that endemism is at most restricted to the archipelagic level. Our results indicate that speciation in the marine environment may occur at spatial scales smaller than 100 km, comparable with some terrestrial systems. Our finding of fine-scale endemism has important consequences for marine conservation and management.

The exploitation of underutilised resources is critical for achieving a sustainable society, and non-edible seaweeds are promising candidates. This study focused on the red alga Portieria hornemannii from Okinawa, Japan, a seaweed with a distinctive aroma, and determined its volatile organic compounds (VOCs) and halogenated secondary metabolites using headspace solid-phase microextraction gas chromatography–mass spectrometry (HS-SPME-GC-MS) at various extraction temperatures. HS-SPME-GC-MS analysis revealed 52 VOCs in Okinawan P. hornemannii, including predominant compounds α-pinenyl bromide (IUPAC name: 2-bromomethyl-6,6-dimethylbicyclo [3.1.1]hept-2-ene; halogenated monoterpene), myrcene disulfide (3-(6-methyl-2-methylidenehept-5-enylidene)dithiirane), and 5,6-dimethyl-1H-benzimidazole, the content of which in the extract increased with increasing extraction temperature from 30 to 60 °C. On the other hand, the β-myrcene (7-methyl-3-methyleneocta-1,6-diene) content, which likely contributes majorly to the distinct fresh odour of the algae, declined as the temperature increased. Furthermore, the proportion of β-myrcene obtained using SPME was significantly higher than that extracted using solvent liquid extraction (SLE) (7.20% in SPME at 30 °C vs. 0.09%, respectively). However, SLE-GC-MS provided a different P. hornemannii volatile profile, allowing for the acquisition of more furan-, alcohol-, ester-, and carboxylic acid-containing compounds. These data provide valuable information, such as a systematic analytical framework for volatiles profiling in the marine macroalgae P. hornemannii, with potential applicability in the development of food and fragrance products.

The chemical investigation of a red alga Portieria hornemannii enabled the identification of three new halogenated monoterpenes (1–3) along with two previously identified metabolites (4 and 5). Their structures were determined by spectroscopic analysis and also by utilizing single-crystal diffraction analysis and quantum chemical calculation, as well as by comparison with literature data. Further corrections for dichloro and dibromo carbons using the sorted training set (STS) method were established in this study to significantly improve the accuracy in GIAO 13C NMR calculation of compounds 1–3. To discover the potential bioactive metabolites from P. hornemannii, the anti-inflammatory activities of all compounds were examined. Compounds 1 and 3–5 showed significant anti-inflammatory activity to inhibit the production of pro-inflammatory cytokines in the LPS-stimulated mature dendritic cells.

Marine algae (seaweeds) have emerged as a promising source in the continuing search for antidiabetic compounds because of their medicinal and nutritional properties. The present study evaluated marine red algae, Portieria hornemannii, for its inhibition of diabetic-linked enzymes (α-amylase, α-glucosidase, and DPP-IV) and antioxidant (DPPH) potential using in vitro assays. Among the tested extracts, ethyl acetate and acetone extract exhibited notable inhibition against α-amylase (IC50: 95.30 μg/mL), α-glucosidase (IC50: 632.5 μg/mL), and DPP-IV (IC50: 36.91 μg/mL). However, the antioxidant activity of the extracts was mild to moderate (17%). Furthermore, the half maximal inhibitory concentration (IC50) of the extracts was found to be non-toxic against mouse macrophage cells (J774) and human red blood cells. Chemical profiling by GC-MS analysis revealed the presence of major bioactive compounds such as phytol, z,z-6,28-heptatriactontadien-2-one, hentriacontane, and l-ascorbic acid. Overall, our findings indicate that the extracts of P. hornemannii reduce postprandial hyperglycemia by inhibiting the release of simple sugars through the inhibition of the enzymes (α-amylase, α-glucosidase, and DPP-IV).

Possible sources of variation in non-polar secondary metabolites of Portieria hornemannii, sampled from two distinct regions in the Philippines (Batanes and Visayas), resulting from different life-history stages, presence of cryptic species, and/or spatiotemporal factors, were investigated. PCA analyses demonstrated secondary metabolite variation between, as well as within, five cryptic Batanes species. Intraspecific variation was even more pronounced in the three cryptic Visayas species, which included samples from six sites. Neither species groupings, nor spatial or temporal based patterns, were observed in the PCA analysis, however, intraspecific variation in secondary metabolites was detected between life-history stages. Male gametophytes (102 metabolites detected) were strongly discriminated from the two other stages, whilst female gametophyte (202 metabolites detected) and tetrasporophyte (106 metabolites detected) samples were partially discriminated. These results suggest that life-history driven variations, and possibly other microscale factors, may influence the variation within Portieria species.

Portieria hornemannii is a common and widespread Indo-Pacific red seaweed. Our studies suggest, however, that P. hornemannii does not represent a single species. Extremely high levels of diversity, based on mitochondrial (cox1, cox2-3 spacer) and chloroplast (rbcL, rbcL-S spacer) markers, are encountered among isolates spanning the entire geographical range of the 'species'. Model based species delineation based on lineage through time plots reveal at least 27 species. These results are corroborated by assessments of DNA barcoding gaps. In the Philippines, these individual lineages possess a near exclusive distribution pattern in the Central Visayas region, with most species restricted to one or a few localities. These observations are in stark contrast with the diversity pattern observed in the northern Batan Island, Batanes where a high sympatric diversity is encountered. Given the high diversity encountered at small geographical scales, we used low-copy nuclear genes (EF2 and Actin) to assess for reproductive isolation among the various lineages encountered in the Philippines. Gene trees of nuclear markers are in full concordance with the phylogenies based on organelle genes, suggesting complete reproductive isolation under natural conditions. Current efforts are dedicated at understanding the causes of this unexpected diversification, which apparently has not been accompanied by significant morphological differentiation. Ecological modes of speciation driven by herbivore interactions are investigated. The algae in question are grazed upon by Aplysia sea hares and are known to produce a wide variety of halogenated monoterpenes which probably act as antigrazing defense mechanisms.

This study is the second of two surveys designed to systematically screen extracts from marine plants for antimicrobial effects against ecologically relevant marine microorganisms, and to compare results on a geographical basis. In the preceding survey, extracts from tropical Atlantic marine algae and seagrasses were screened in growth inhibition assays against the pathogenic fungus Lindra thalassiae, the saprophytic fungus Dendryphiella salina, the saprophytic stramenopiles, Halophytophthora spinosa and Schizochytrium aggregatum, and the pathogenic bacterium Pseudoaltermonas bacteriolytica. In this study, the same assay microorganisms were used to examine the antimicrobial effects of lipophilic and hydrophilic extracts from 54 species of marine algae and two species of seagrasses collected from Indo-Pacific reef habitats. Overall, 95% of all species surveyed in this study yielded extracts that were active against one or more, and 77% yielded extracts that were active against two or more assay microorganisms. Broad-spectrum activity against three or four assay microbes was observed in the extracts from 50 to 21% of all species, respectively. Extracts from the green alga Bryopsis pennata and the red alga Portieria hornemannii inhibited the growth of all assay microorganisms. Given that antimicrobial activity was prevalent among extracts of Indo-Pacific marine plants, it is interesting to note that the inhibitory effects of each extract varied considerably between the assay microorganisms. Overall, H. spinosa and D. salina were the most susceptible while L. thalassiae, S. aggregatum, and P. bacteriolytica were the most resistant to the extracts tested. These results provide good evidence that antimicrobial chemical defenses are widespread among Indo-Pacific marine plants. Further, the activity profiles of plant extracts suggest that antimicrobial secondary metabolites can have pathogen-selective or broad-spectrum effects. To confirm these results, chemical studies will be needed to isolate and characterize the compounds responsible for the observed antimicrobial activities. [PUBLICATION ABSTRACT]

Marine algae produce a variety of secondary metabolites that function as herbivore deterrents. Algal metabolites, however, often fail to deter damage by some herbivores such as mesograzers that both live and feed on their host alga. In addition, the degree to which intraspecific chemical variation in an alga affects a mesograzer's feeding behavior and its ability to deter predators is poorly understood. The red alga Portieria hornemannii contains the secondary metabolites apakaochtodene A and B, which have been shown to vary in concentration among sites on Guam and act as significant deterrents to fish feeding. On Guam, the sea hare Aplysia parvula preferred and grew best when fed its algal host P. hornemannii. However, high concentrations of P. hornemannii crude extract and the pure compounds apakaochtodene A and B acted as feeding deterrents to A. parvula. Despite differences among sites in the levels of apakaochtodenes A and B, A. parvula showed no significant preference for P. hornemannii from any one location. Aplysia parvula found on P. hornemannii sequestered apakaochtodenes, and both whole animals and body parts were unpalatable to reef fishes. Sea hares found on the red alga Acanthophora spicifera, which contains no unpalatable secondary metabolites, had no apakaochtodene compounds and were eaten by fishes. This observation is consistent with the hypothesis that diet-derived algal metabolites in sea hares play a role in deterring predation.

Apakaochtodenes A and B, which are halogenated monoterpenes and the major secondary metabolites in Portieria hornemannii, are effective feeding deterrents toward herbivorous reef fishes on Guam. A reciprocal transplant study was conducted to determine the relative importance of environmental versus genetic factors influencing site-to-site differences in the amount of apakaochtodenes produced. The study sites were chosen for characteristically high (Anae Island) and low (Gun Beach) apakaochtodene levels. Algae collected from Anae Island and Gun Beach differed significantly in concentrations of apakaochtodene B at the start of the experiment, but by the end they had almost the same amount of the metabolite because the level had decreased in plants at Anae Island. Additionally, algae from Anae Island had relatively high levels of apakaochtodene A (60-90% of apakaochtodene B concentration), whereas this compound was rarely detected in Gun Beach algae. Transplantation t o a different site had no significant effect on the levels of the apakaochtodenes, other than a decrease in concentration that might have resulted from handling the algae. Our data indicate a strong site-to-site difference in apakaochtodene levels in P. hornemannii on Guam, notable interplant variation in the levels of the compounds among thalli within the same site, and some evidence for temporal variation in levels of these compounds over a period of four weeks.[PUBLICATION ABSTRACT]