Variability of Non-Polar Secondary Metabolites in the Red Alga Portieria

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

Variability of Non-Polar Secondary Metabolites in the Red Alga Portieria

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

Chaetomorpha philippinensis (Cladophorales, Chlorophyta), a new marine microfilamentous green alga from tropical waters

A new marine microfilamentous green alga, Chaetomorpha philippinensis Leliaert sp. nov., is described as an epiphyte on Chaetomorpha vieillardii from shallow subtidal habitats in the Philippines. Phylogenetic analyses of large subunit rDNA and rDNA internal transcribed spacer (ITS) sequences show that the new tropical species is sister to the cold-water Chaetomorpha norvegica, from which it is genetically clearly distinct but morphologically almost indistinguishable. Chaetomorpha philippinensis is characterized by minute, straight or curved, unbranched, erect filaments up to 300 mu m long and 7-17 mu m in diameter, attached by a basal, hapteroid holdfast. Filaments in culture are similar in morphology but grow considerably longer with slightly larger cells. The cylindrical cells are multinucleate with up to eight nuclei (up to 18 in culture). Cells contain a single, parietal, lobed chloroplast with numerous small perforations and one to several pyrenoids. Zoosporangia develop by transformation of apical and subapical cells with zoids emerging through a domed pore in the apical, middle or basal part of the cell

DNA-based species delimitation in algae

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Evolution and species boundaries of the Portieria-complex (Rhodophyta: Gigartinales)

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 Batanes Islands, 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 Applysia sea slugs and are known to produce a wide variety of halogenated monoterpenes which act as antigrazing defense mechanisms

Extensive cryptic species diversity and fine-scale endemism in the marine red alga Portieria in the Philippines

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

Patterns and drivers of species diversity in the Indo-Pacific red seaweed Portieria

Aim: Biogeographical processes underlying Indo-Pacific biodiversity patterns have been relatively well studied in marine shallow water invertebrates and fishes, but have been explored much less extensively in seaweeds, despite these organisms often displaying markedly different patterns. Using the marine red alga Portieria as a model, we aim to gain understanding of the evolutionary processes generating seaweed biogeographical patterns. Our results will be evaluated and compared with known patterns and processes in animals. Location Indo-Pacific marine region. Methods: Species diversity estimates were inferred using DNA-based species delimitation methods. Historical biogeographical patterns were inferred based on a six-gene time-calibrated phylogeny, distribution data of 802 specimens, and probabilistic modelling of geographical range evolution. The importance of geographical isolation for speciation was further evaluated by population genetic analyses at the intraspecific level. Results: We delimited 92 candidate species, most with restricted distributions, suggesting low dispersal capacity. Highest species diversity was found in the Indo-Malay Archipelago (IMA). Our phylogeny indicates that Portieria originated during the late Cretaceous in the area that is now the Central Indo-Pacific. The biogeographical history of Portieria includes repeated dispersal events to peripheral regions, followed by long-term persistence and diversification of lineages within those regions, and limited dispersal back to the IMA. Main conclusions: Our results suggest that the long geological history of the IMA played an important role in shaping Portieria diversity. High species richness in the IMA resulted from a combination of speciation at small spatial scales, possibly as a result of increased regional habitat diversity from the Eocene onwards, and species accumulation via dispersal and/or island integration through tectonic movement. Our results are consistent with the biodiversity feedback model, in which biodiversity hotspots act as both "centres of origin" and "centres of accumulation," and corroborate previous findings for invertebrates and fish that there is no single unifying model explaining the biological diversity within the IMA