Browsing by Author "Valero, Myriam"
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- ItemAfter a catastrophe, a little bit of sex is better than nothing: Genetic consequences of a major earthquake on asexual and sexual populations(2020) Becheler, Ronan; Guillemin, Marie-Laure; Stoeckel, Solenn; Mauger, S.; Saunier, Alice; Brante Ramírez, Antonio Javier; Destombe, Christophe; Valero, Myriam
- ItemDeep reefs are climatic refugia for genetic diversity of marine forests(2015) Assis, Jorge; Castilho Coelho, Nelson; Lamy, Thomas; Valero, Myriam; Alberto, Filipe; Álvares Serrão, Ester
- ItemEvidence for parasite-mediated selection during short-lasting toxic algal blooms(2016) Blanquart, François; Valero, Myriam; Souza, Catharina Alves de; Dia, Aliou; Lepelletier, Frédéric; Bigeard, Estelle; Jeanthon, Christian; Destombe, Christophe; Guillou, Laure
- ItemHigh-density genetic map and identification of QTLs for responses to temperature and salinity stresses in the model brown alga Ectocarpus(2017) Avia, K.; Coelho, S.; Montecinos Arismendi, Gabriel José; Cormier, A.; Lerck, F.; Mauger, S.; Faugeron, Sylvain Wielfrid; Valero, Myriam; Cock, J.; Boudry, P.
- ItemKallymenia crouaniorum (Kallymeniaceae, Rhodophyta), a new red algal species from the Laminaria hyperborea understorey community(2014) Robuchon, Marine; Le Gall, Line; Gey, Delphine; Valero, Myriam; Verges, AlbaIn this paper we describe Kallymenia crouaniorum Verges & Le Gall, sp. nov. (Kallymeniaceae), a new marine red alga from the north-eastern Atlantic Ocean. rbcL and LSU sequences of this species, previously misidentified in the field as Kallymenia reniformis, diverged from those of other Kallymenia species by at least 7.5% and 5.2%, respectively. Kallymenia crouaniorum also has a set of distinctive vegetative and reproductive characteristics, including a deeply lacerate frond, a short stipe, dentate margins, large cortical cells up to 110 mu m in diameter, highly refractive stellate medullary cells with arms up to 1000 mu m in length, and a monocarpogonial branch system. Molecular phylogenies inferred from rbcL and LSU data indicated, albeit with weak support, that this new species is a sister taxon of a lineage encompassing the generitype K. reniformis, as well as most species of Kallymenia included in the phylogenetic analysis. The main morphological characters that delineate monocarpogonial Kallymenia species are presented. Moreover, after reviewing the literature and several herbarium specimens, we found in the Weber-van Bosse Herbarium a specimen collected at Roscoff in August 1894 with the anatomical characters of the species described here, confirming that this newly described species has in fact been overlooked and is not a recent introduction.
- ItemParallelisable non-invasive biomass, fitness and growth measurement of macroalgae and other protists with nephelometry(2020) Calmes, B.; Strittmatter, M.; Jacquemin, B.; Perrineau, M. M.; Rousseau, C.; Badis, Y.; Cock, J. M.; Destombe, Christophe; Valero, Myriam; Gachon, C. M. M.
- ItemPhylogeographic analyses of the 30°S south-east Pacific biogeographic transition zone establish the occurrence of a sharp genetic discontinuity in the kelp Lessonia nigrescens: Vicariance or parapatry?(2009) Tellier, Florence; Meynard, Andres P.; Correa, Juan A.; Faugeron, Sylvain; Valero, MyriamPhylogeographic studies are lacking in the Southern Hemisphere, and in particular in the south-eastern Pacific. To infer the possible scenario for the debated biogeographic transition zone located at 30-33 degrees S along the Chilean coast, we investigated whether there is a concordance between the phylogeographic pattern and the biogeographic transition in the intertidal kelp Lessonia nigrescens; whose distribution is continuous across this transition zone. Using a combination of four makers located in the three genomic compartments (chloroplast, mitochondria and nucleus), we showed the presence of two main divergent lineages, possibly cryptic species. There was an exact match of the phylogeographic break with the 30 degrees S biogeographic transition zone, suggesting a common origin. The combined information given by the multilocus approach and by the population analysis suggested the occurrence of a budding speciation, with a northward range expansion. (C) 2009 Elsevier Inc. All rights reserved.
- ItemPossible role of a mitochondrial genome rearrangement in maintaining the spatial segregation of two cryptic species of the Lessonia nigrescens species complex(2011) Tellier, Florence; Faugeron, Sylvain; Valero, MyriamIn numerous taxa, studies have reported the co-occurrence of several copies for a single mitochondrial marker (heteroplasmy), leading to incorrect phylogenetic inferences if not detected. While this phenomenon has been widely investigated in terrestrial taxa, it remains largely unexplored in marine algae. Here we report the detection of heteroplasmy in the Lessonia nigrescens species complex. This work aimed to identify the distinct fragments and to determine their geographic extent in the distribution range of two kelp species. Using phylogenetic reconstructions of a mitochondria! DNA marker (atp8/trnS intergenic region), we suggest that a duplication event occurred, either with or without transfer of the copy to the nucleus. The corresponding sequences constituted a new monophyletic clade, distinct from those previously described in L. nigrescens, hence discarding the interspecific hybridization and intraspecific biparental transmission hypotheses. The characterization of 652 individuals sampled along 2,500 km of coastline revealed that the duplication was absent in the Northern species, but of high frequency in the northernmost populations of the Southern species. Because the duplication is restricted to the parapatric contact zone between the two species, our findings open new perspectives about the importance of reproductive isolation mechanisms and local adaptation in the origin and persistence of this pattern.
- ItemSEX RATIO VARIATION IN THE LESSONIA NIGRESCENS COMPLEX (LAMINARIALES, PHAEOPHYCEAE): EFFECT OF LATITUDE, TEMPERATURE, AND MARGINALITY(WILEY, 2011) Oppliger, Luz Valeria; Correa, Juan A.; Faugeron, Sylvain; Beltran, Jessica; Tellier, Florence; Valero, Myriam; Destombe, ChristopheLittle is known about variation of sex ratio, the proportion of males to females, in natural populations of seaweed, though it is a major determinant of the mating system. The observation of sexual chromosomes in kelps suggested that sex is partly genetically determined. However, it is probably not purely genetic since the sex ratio can be modified by environmental factors such as salinity or temperature. In this paper, sex ratio variation was studied in the kelp Lessonia nigrescens Bory complex, recently identified as two cryptic species occurring along the Chilean coast: one located north and the other south of the biogeographic boundary at latitude 29 degrees-30 degrees S. The life cycle of L. nigrescens is characterized by an alternation of microscopic haploid gametophytic individuals and large macroscopic fronds of diploid sporophytes. The sex ratio was recorded in progenies from 241 sporophytic individuals collected from 13 populations distributed along the Chilean coast in order (i) to examine the effect of an environmental gradient coupled with latitude, and (ii) to compare marginal populations to central populations of the two species. In addition, we tested the hypothesis that the sex ratios of the two cryptic species would be affected differently by temperature. First, our results demonstrate that sex ratio seems to be mainly genetically determined and temperature can significantly modify it. Populations of the northern species showed a lower frequency of males at 14 degrees C than at 10 degrees C, whereas populations of the southern species showed the opposite pattern. Second, both species displayed an increased variation in sex ratio at the range limits. This greater variation at the margins could be due either to differential mortality between sexes or to geographic parthenogenesis (asexual reproduction).
- ItemThe importance of having two species instead of one in kelp management: the Lessonia nigrescens species complex(2011) Tellier, Florence; Alonso Vega, J. M.; Broitman, Bernardo R.; Vasquez, Julio A.; Valero, Myriam; Faugeron, SylvainNatural resource management requires extensive knowledge of the biology of the organisms and their responses to ecological and anthropogenic processes. While species are commonly used as management units, the presence of cryptic species morphologically indistinguishable, but with different biological characteristics may hinder the design of appropriate management and conservation measures. Thus, correctly assigning individuals to species is of particular importance and challenges current management approaches in seaweeds, which are highly plastic morphologically. After a synthesis of the species definitions, we show an example of the challenges of managing cryptic species with the Chilean kelp Lessonia nigrescens. We review phylogenetic, biological and ecological evidence indicating that this economically important intertidal species is composed of two cryptic species. In the face of increasing global demand for kelp, an intensified impact of harvesting pressure is observed around the region where both cryptic species find their northern and southern edge of their geographic distributions, around 30 S. We recommend special management strategies targeting harvested areas around such range edge populations. Our synthesis highlights the importance of having two species that are ecologically and genetically different. In addition, the cryptic species may diverge in biochemical composition, opening new perspectives for the alginates' industry. The capacity of conservation and management programs to correctly distinguish new species is of particular importance as numerous cryptic species are constantly being discovered in seaweeds, including kelps.
- ItemThe Rhodoexplorer Platform for Red Algal Genomics and Whole-Genome Assemblies for Several Gracilaria Species(2023) Lipinska, Agnieszka P.; Krueger-Hadfield, Stacy A.; Godfroy, Olivier; Dittami, Simon M.; Ayres-Ostrock, Ligia; Bonthond, Guido; Brillet-Gueguen, Loraine; Coelho, Susana; Corre, Erwan; Cossard, Guillaume; Destombe, Christophe; Epperlein, Paul; Faugeron, Sylvain; Ficko-Blean, Elizabeth; Beltran, Jessica; Lavaut, Emma; Le Bars, Arthur; Marchi, Fabiana; Mauger, Stephane; Michel, Gurvan; Potin, Philippe; Scornet, Delphine; Sotka, Erik E.; Weinberger, Florian; de Oliveira, Mariana Cabral; Guillemin, Marie-Laure; Plastino, Estela M.; Valero, MyriamMacroalgal (seaweed) genomic resources are generally lacking as compared with other eukaryotic taxa, and this is particularly true in the red algae (Rhodophyta). Understanding red algal genomes is critical to understanding eukaryotic evolution given that red algal genes are spread across eukaryotic lineages from secondary endosymbiosis and red algae diverged early in the Archaeplastids. The Gracilariales is a highly diverse and widely distributed order including species that can serve as ecosystem engineers in intertidal habitats and several notorious introduced species. The genus Gracilaria is cultivated worldwide, in part for its production of agar and other bioactive compounds with downstream pharmaceutical and industrial applications. This genus is also emerging as a model for algal evolutionary ecology. Here, we report new whole-genome assemblies for two species (Gracilaria chilensis and Gracilaria gracilis), a draft genome assembly of Gracilaria caudata, and genome annotation of the previously published Gracilaria vermiculophylla genome. To facilitate accessibility and comparative analysis, we integrated these data in a newly created web-based portal dedicated to red algal genomics (https://rhodoexplorer.sb-roscoff.fr). These genomes will provide a resource for understanding algal biology and, more broadly, eukaryotic evolution.
- ItemVariation in Thermal Tolerance of the Giant Kelp's Gametophytes: Suitability of Habitat, Population Quality or Local Adaptation?(2022) Becheler, Ronan; Haverbeck, Daniela; Clerc, Corentin; Montecinos, Gabriel; Valero, Myriam; Mansilla, Andres; Faugeron, SylvainThe giant kelp Macrocystis pyrifera is a cosmopolitan species of cold-temperate coasts. Its South-American distribution ranges from Peru to Cape Horn and Argentina, encompassing a considerable temperature gradient, from 3 to 20 degrees C. Temperature is known to strongly affect survival, growth and reproduction of many kelp species, and ongoing global warming is already eroding their range distribution. Their response to thermal variability was shown to vary among genetically differentiated regions and populations, suggesting a possible adaptive divergence in thermal tolerance traits. This study aimed at testing the existence of local adaptation in the giant kelp, in regions separated by up to 4000km and strong thermal divergence. Two complementary experiments mimicked reciprocal transplants through a common garden approach, each habitat being represented by a given temperature corresponding to the regional average of the sampled populations. Several proxies of fitness were measured in the haploid stage of the kelp, and sympatric versus allopatric conditions (i.e. individuals at the temperature of their region of origin versus in a different temperature and versus individuals from other regions in that temperature) were compared. Additionally, a heat wave at 24 degrees C was applied to measure the tolerance limits of these gametophytes. A significant interaction between experimental temperature and region of origin revealed that temperature tolerance varied among regions. However, depending on the fitness parameter measured, high latitude populations from the sub-Antarctic region were not always less heat resilient than populations from the warmer region of Peru. Even at 24 degrees C, a temperature that is exceptionally reached in the southernmost part of the kelp's natural habitat, all the gametophytes survived, although with strong differences in other traits among regions and populations within regions. This large range of temperature tolerance supports the idea of kelp gametophytes being a resistant stage. Finally, local adaptation sensu stricto was not detected. Fertility was more influenced by the geographic origin than by temperature, with possible effects of marginal conditions at the extremes of the distribution range. The latter results also suggest that stochastic dynamics such as genetic drift restricts adaptive processes in some populations of M. pyrifera.