Journal Articles
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- Molecular-assisted taxonomic study on the Sargassum C.Agardh (Fucales, Phaeophyceae) in Northwestern Luzon, PhilippinesSantiañez, Wilfred John E.; Lastimoso, John Michael L.; Hoshino, Masakazu; Villafuerte, Brix Nester Q.; Kogame, Kazuhiro; Trono, Gavino C. (Museum National d'Histoire Naturelle, 2023-10-18)The diversity of the brown algal genus Sargassum C.Agardh in the Philippines is the highest in the tropical western Pacific Ocean. However, most studies on Philippine Sargassum are based on morphoanatomies and the assumption that the genus is very diverse in the country has never been tested based on molecular information. Considering that many Sargassum species are highly polymorphic and the recent advance on Sargassum systematics facilitated by molecular phylogenetic studies, we believe that the species of Sargassum from the Philippines should now be reassessed with the tools of molecular taxonomy. We present here the results of our molecular-assisted taxonomic studies on the Sargassum of the northern Philippines, particularly along the coasts of four coastal provinces in northwestern Luzon (i.e., Ilocos Norte, Ilocos Sur, La Union, and Pangasinan). We recognized three distinct species lineages, namely, Sargassum aquifolium (Turner) C.Agardh, Sargassum ilicifolium (Turner) C.Agardh, and Sargassum polycystum C.Agardh based on our molecular analyses of 74 specimens from our study areas. Our morphological observations on the range of characters of these species also suggest that several common Sargassum taxa in the Philippines have been misidentified. Particularly, specimens previously attributed to S. kushimotense Yendo should be referred as S. aquifolium while the widely distributed and highly plastic S. ilicifolium is often confused and identified in the Philippines under several names including S. crassifolium J.Agardh, S. cristaefolium C.Agardh, and S. turbinarioides Grunow. Taken together, our results suggest that Sargassum biodiversity in the Philippines may have been inflated by misidentifications, and, that species diversity is actually much lower than initially thought.
- Trans-Arctic asymmetries, melting pots and weak species cohesion in the low-dispersal amphiboreal seaweed Fucus distichusNeiva, João; Assis, Jorge; Fragkopoulou, Eliza; Pearson, Gareth A.; Raimondi, Peter T.; Anderson, Laura; Krause-Jensen, Dorte; Marbà, Núria; Want, Andrew; Selivanova, Olga; Nakaoka, Masahiro; Grant, W. Stewart; Konar, Brenda; Roleda, Michael Y.; Sejr, Mikael K.; Paulino, Cristina; Serrão, Ester A. (Frontiers Media SA, 2024-04-18)Amphiboreal taxa are often composed of vicariant phylogroups and species complexes whose divergence and phylogeographic affinities reflect a shared history of chronic isolation and episodic trans-Arctic dispersal. Ecological filters and shifting selective pressures may also promote selective sweeps, niche shifts and ecological speciation during colonization, but these are seldom considered at biogeographical scales. Here we integrate genetic data and Ecologic Niche Models (ENMs) to investigate the historical biogeography and cohesion of the polymorphic rockweed Fucus distichus throughout its immense amphiboreal range, focusing on trans-Arctic asymmetries, glacial/interglacial dynamics, and integrity of sympatric eco-morphotypes. Populations were sampled throughout the Pacific and the Atlantic, from southern rear-edges to the high-Arctic. They were genotyped for seven microsatellites and an mtDNA spacer, and genetic diversity and structure were assessed from global to local scales. ENMs were used to compare niche divergence and magnitude of post-glacial range shifts in Pacific versus Atlantic sub-ranges. Haplotypic and genotypic data revealed distinct and seemingly isolated Pacific vs Arctic/Atlantic gene-pools, with finer-scale regional sub-structuring pervasive in the Pacific. MtDNA diversity was highly structured and overwhelmingly concentrated in the Pacific. Regionally, Alaska showed the highest intra-population diversity but the lowest levels of endemism. Some sympatric/parapatric ecotypes exhibited distinct genotypic/haplotypic compositions. Strikingly, niche models revealed higher Pacific tolerance to maximum temperatures and predicted a much more consolidated presence in the NE Atlantic. Glacial and modern ranges overlapped extensively in the Pacific, whereas the modern Atlantic range was largely glaciated or emerged during the Last Glacial Maximum. Higher genetic and ecogeographic diversity supports a primary Pacific diversification and secondary Atlantic colonization, also likely reflecting the much larger and more stable climatic refugia in the Pacific. The relic distribution and reduced ecological/morphological plasticity in the NE Atlantic are hypothesized to reflect functional trans-Arctic bottlenecks, recent colonization or competition with congeners. Within the Pacific, Alaska showed signatures of a post-glacial melting pot of eastern and southern populations. Genetic/ecotypic variation was generally not sufficiently discontinuous or consistent to justify recognizing multiple taxonomic entities, but support a separate species in the eastern Pacific, at the southern rear-edge. We predict that layered patterns of phylogeographic structure, incipient speciation and niche differences might be common among widespread low-dispersal amphiboreal taxa.
- Seaweed as a resilient food solution after a nuclear warJehn, Florian Ulrich; Dingal, Farrah Jasmine; Mill, Aron; Harrison, Cheryl; Ilin, Ekaterina; Roleda, Michael Y.; James, Scott C.; Denkenberger, David (American Geophysical Union, 2024-01-09)Abrupt sunlight reduction scenarios such as a nuclear winter caused by the burning of cities in a nuclear war, an asteroid/comet impact or an eruption of a large volcano inject large amounts of particles in the atmosphere, which limit sunlight. This could decimate agriculture as it is practiced today. We therefore need resilient food sources for such an event. One promising candidate is seaweed, as it can grow quickly in a wide range of environmental conditions. To explore the feasibility of seaweed after nuclear war, we simulate the growth of seaweed on a global scale using an empirical model based on Gracilaria tikvahiae forced by nuclear winter climate simulations. We assess how quickly global seaweed production could be scaled to provide a significant fraction of global food demand. We find seaweed can be grown in tropical oceans, even after nuclear war. The simulated growth is high enough to allow a scale up to an equivalent of 45% of the global human food demand (spread among food, animal feed, and biofuels) in around 9–14 months, while only using a small fraction of the global ocean area. The main limiting factor being the speed at which new seaweed farms can be built. The results also show that the growth of seaweed increases with the severity of the nuclear war, as more nutrients become available due to increased vertical mixing. This means that seaweed has the potential to be a viable resilient food source for abrupt sunlight reduction scenarios.
- Physiological and biochemical characterization of new wild strains of Kappaphycus alvarezii (Gigartinales, Rhodophyta) cultivated under land-based hatchery conditionsNarvarte, Bienson Ceasar V.; Hinaloc, Lourie Ann R.; Genovia, Tom Gerald T.; Gonzaga, Shienna Mae C.; Tabonda-Nabor, April Mae; Roleda, Michael Y. (Elsevier, 2022-12)The red alga Kappaphycus alvarezii is globally cultivated as a major source of k-carrageenan. Farming of this species through clonal propagation has been confined to a few good-quality commercial strains. After more than 50 years of successful cultivation and high productivity, the production of K. alvarezii in most “cottonii”-producing countries like the Philippines had declined in recent decades. This can be attributed to low genetic variability, making “old” cultivars more susceptible to environmental stressors, pests (epi- and endophytes) and diseases (e.g., ice-ice). Hence, the establishment of new cultivars from wild strains with desirable traits may provide alternative seedstocks with different genetic makeup from the currently farmed cultivars. Here, we examined the physiological and biochemical properties of 10 new wild strains of K. alvarezii, belonging to four non-commercially cultivated haplotypes, collected from Eastern Samar, Philippines. These strains were cultivated in an outdoor, land-based hatchery with ambient light and flow-through, nutrient replete seawater. Growth rates, ranging from 0.44 % to 3.74 % d-1, significantly varied among the strains but did not significantly vary among haplotypes. The cultivars also showed a notable change in color and morphology as they adapted to hatchery conditions. Pigments and total phenolic content did not significantly vary among cultivars. Proximate analysis showed that the dry biomass of all K. alvarezii strains was composed mainly of ash (ranging from 39.2 % to 51.0 %), followed by carbohydrate (ranging from 26.0 % to 35.3 %), and with trace amounts of proteins (ranging from 1.02 % to 4.61 %). Moreover, tissue stoichiometry (C, N and P) was comparable among the 10 strains. Considering the promising growth performance of strain SamW-014 under hatchery condition, we recommend its cultivation at sea and conduct corresponding carrageenan yield and quality analyses on its raw dried biomass. Among the 10 strains, five others are also of interest and for consideration. Thereafter, selected strain(s) will be introduced to seaweed farmers for future cultivation to increase biomass production, harvest yields, and income.