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Iván Gómez - One of the best experts on this subject based on the ideXlab platform.

  • comparison of different techniques for the preservation and extraction of phlorotannins in the kelp Lessonia spicata phaeophyceae assays of dpph orac pgr and orac fl as testing methods
    Journal of Applied Phycology, 2016
    Co-Authors: Edgardo Cruces, Y Rojaslillo, Eduardo Ramirezkushel, Elias Atala, Camilo Lopezalarcon, Eduardo Lissi, Iván Gómez
    Abstract:

    Preservation, storage, and safe transport of samples are key factors affecting brown algal phlorotannin (phenolics) quantification, their extraction yield, and antioxidant activity. This is especially relevant when field sampling is carried out in remote areas. The objective of the present study was to evaluate and compare five preservation (frozen control, freeze-dried, silica-dried, oven-dried, and air-dried) and two extraction methods (“rapid” and “traditional” extraction) of phlorotannins in the kelp Lessonia spicata (former Lessonia nigrescens). The antioxidant power of the samples treated with the different drying methods was compared through three different in vitro antioxidant assays: 2,2-diphenyl-1-picrylhydrazyl (DPPH) and oxygen radical absorbance capacity (ORAC) methods, employing fluorescein (ORAC-FL) and pyrogallol red (ORAC-PGR) as target molecules. The results of the testing methods indicated that freeze-drying afforded the best extraction yields of phlorotannins (18–30 % higher than control using frozen material) whereas concentrations from samples dried in silica and oven averaged between 17 and 20 % lower than control. The antioxidant activity of phlorotannins measured using the DPPH test decreased significantly in samples kept dried compared to that in control, with activities varying from 65 (freeze-dried) to 21 % (air-dried). Accordingly, with ORAC-PGR and ORAC-FL indexes, sample preservation employing silica-drying or air-drying caused a high decrease of the antioxidant activity of polyphenols. No differences in both total phlorotannin concentration and antioxidant activity between the two extraction methods were found.

  • Variable feeding behavior in Orchestoidea tuberculata (Nicolet 1849): Exploring the relative importance of macroalgal traits
    Journal of Sea Research, 2014
    Co-Authors: Cristian Duarte, Iván Gómez, Karin Acuña, Jorge Navarro, Eduardo Jaramillo, Pedro A. Quijón
    Abstract:

    Abstract The feeding behavior of algal consumers inhabiting sandy beaches and the consequences of this behavior on their performance are poorly understood. Food quality has been shown to influence the food preference of algal consumers. However, food preference can often be altered or subordinated to habitat choice. This study analyzes the feeding behavior (preference and consumption rate), absorption efficiency and growth rates of the talitrid amphipod Orchestoidea tuberculata (Nicolet, 1849) in relation to the nutritional characteristics of two of the most common macroalgae stranded in the Chilean north-central region. Our experiments show that these amphipods prefer Macrocystis integrifolia over Lessonia nigrescens when presented with fresh fragments of both algae simultaneously. However, this preference did not match the performance of the amphipods when reared on diets of a single algal species: in that growth rates were not different. These results suggest that M. integrifolia is not a superior food item compared to L. nigrescens . The lower content of proteins and total organic matter found in M. integrifolia supports this interpretation. The preference of the amphipods for L. nigrescens over M. integrifolia when dry powdered algae of each species were provided (artificial food), suggested that some aspect of the physical structure of these two algae determined food preference. When the amphipods were maintained with each of the algal species in no choice experiments, they consumed 2 times more M. integrifolia , but showed higher absorption efficiency on L. nigrescens . These results suggest that food quantity and not absorption efficiency was used to compensate for the lower nutritional quality of M. integrifolia . The feeding behavior documented in this study differs significantly from that observed in populations of the same species inhabiting southern Chile, cautioning against generalizing results obtained even within a single species. Our results suggest that physical features rather than chemical characteristics of the food drive feeding preferences, including the potential (indirect) roles played by the fronds of these seaweeds as refuges against competition and desiccation.

  • Interactive effects of UV radiation and enhanced temperature on photosynthesis, phlorotannin induction and antioxidant activities of two sub-Antarctic brown algae
    Marine Biology, 2013
    Co-Authors: Edgardo Cruces, Pirjo Huovinen, Iván Gómez
    Abstract:

    Lessonia nigrescens and Durvillaea antarctica, two large sub-Antarctic brown algae from the southern Chilean coast, were exposed to solar UV radiation in an outdoor system during a summer day (for 11 h) as well as to artificial UV radiation under controlled laboratory conditions at two temperatures (15 and 20 °C) for 72 h. Chlorophyll a fluorescence–based photoinhibition of photosynthesis was measured during the outdoor exposure, while electron transport rates, lipid peroxidation, antioxidant activity and content of phlorotannins were determined at different time intervals during the laboratory exposure. Under natural solar irradiances in summer, both species displayed well-developed dynamic photoinhibition: F _v/ F _m values decreased by 70 % at noon coinciding with the levels of PAR >1,500 μmol m^−2 s^−1 and UV-B radiation >1 W m^−2 and recovered substantially in the afternoon. In treatments including UV radiation, recovery in D. antarctica started already during the highest irradiances at noon. The results from laboratory exposures revealed that (a) elevated temperature of 20 °C exacerbated the detrimental effects of UV radiation on photochemical parameters ( F _v/ F _m and ETR); (b) peroxidative damage measured as MDA formation occurred rapidly and was strongly correlated with the decrease in F _v/ F _m, especially at elevated temperature of 20 °C; (c) the antioxidant activity and increases in soluble phlorotannins were positively correlated mainly in response to UV radiation; (d) phlorotannins were rapidly induced but strongly impaired at 20 °C. In general, short-term (2–6 h) exposures to enhanced UV radiation and temperature were effective to activate the photochemical and biochemical defenses against oxidative stress, and they continued operative during 72 h, a time span clearly exceeding the tidal or diurnal period. Furthermore, when algae were exposed to dim light and control temperature of 15 °C for 6 h, F _v/ F _m increased and lipid peroxidation decreased, indicating consistently that algae retained their ability for recovery. D. antarctica was the most sensitive species to elevated temperature for prolonged periods in the laboratory. Although no conclusive evidence for the effect of the buoyancy of fronds was found, the interspecific discrepancies in thermo-sensitivity in the UV responses found in this study are consistent with various ecological and biogeographical differences described for these species.

  • induction of phlorotannins during uv exposure mitigates inhibition of photosynthesis and dna damage in the kelp Lessonia nigrescens
    Photochemistry and Photobiology, 2010
    Co-Authors: Iván Gómez, Pirjo Huovinen
    Abstract:

    Phlorotannins of brown algae are multifunctional compounds with putative roles in herbivore deterrence, antioxidation and as primary cell wall components. Due to their peripheral localization and absorption at short wavelengths, a photoprotective role is suggested. We examined the induction of phlorotannins by artificial UV radiation in the intertidal kelp Lessonia nigrescens and whether they attenuate the inhibition of photosynthesis and DNA damage, two major detrimental effects of UV. The soluble and cell wall-bound fractions of phlorotannins were quantified in blades collected in summer and winter. Major findings were that (1) the synthesis of phlorotannins (both forms) was induced by UV only in summer; (2) the induction was fast (within 3 days); and (3) there was a positive relationship between of the contents of insoluble phlorotannins and the suppression of photoinhibition and DNA damage, measured as formation of cyclobutane pyrimidine dimers and 6-4 photoproducts. Overall, the photoprotective role of phlorotannins appears to respond to an interplay between the external UV stimulus, seasonal acclimation and intrinsic morpho-functional processes. In summer, when algae are naturally exposed to high UV irradiances, soluble phlorotannins are induced, while their transition to insoluble phlorotannins could be related with the growth requirements, as active blade elongation occurs during this season.

  • Feeding preferences of the sandhopper Orchestoidea tuberculata: The importance of algal traits
    Hydrobiologia, 2010
    Co-Authors: Cristian Duarte, Karin Acuña, Jorge Navarro, Iván Gómez
    Abstract:

    Factors such as nutritional quality and the secondary metabolite content of food resources have been shown to influence the feeding behavior of herbivores in many marine habitats. For intertidal macroalgae consumers on sandy beaches, the influence of these factors on feeding behavior and the consequences on their performance is poorly understood. In this study, we evaluated the relationships of nutritional quality, chemical defenses (phlorotannins), and the structure of three macroalgal species that form the bulk of imported wrack subsidies to beaches in southern Chile, with the feeding behavior, absorption efficiency, and growth rate of the talitrid amphipod Orchestoidea tuberculata, one of the most abundant organisms in this environment. The amphipods preferred Durvillaea antarctica over Lessonia nigrescens and Macrocystis pyrifera when simultaneously offered fresh pieces of each alga. Similar results were observed when artificial food made of dry powdered algae of each species was provided, suggesting that the structure of these three algae did not influence preference. The performance of amphipods when reared on a diet of a single algal species matched feeding preferences; higher growth rates were observed in treatments with the preferred alga, D. antarctica. These results imply that D. antarctica is a superior food item for O. tuberculata when compared to L. nigrescens or M. pyrifera, and also that the alga’s intrinsic quality (i.e., not structure) may influence dietary preference in these consumers. The higher content of proteins and carbohydrates found in D. antarctica may explain why this macroalga represents better quality food for O. tuberculata. Phlorotannin content did not have obvious negative effects on diet choice or growth, as D. antarctica, the alga with greater content of these secondary metabolites, was preferred and associated with higher growth rates of O. tuberculata. However, it is necessary to emphasize that the low phlorotannins concentrations registered in the three macroalgae species examined in this study, may not have been sufficient to deter O. tuberculata. When the amphipods were fed with each alga individually, they consumed significantly higher quantities of D. antarctica, which suggests that O. tuberculata did not eat more to compensate for the lower nutritional quality of the other algal species in order to maintain growth. Nor was compensation for lower food quality achieved by increasing absorption efficiency. Our results imply that the composition of the macroalgae arriving on the beach can significantly affect the performance and subsequent life history traits of O. tuberculata and by extension other amphipod species.

Florence Tellier - One of the best experts on this subject based on the ideXlab platform.

  • Etude des processus de spéciation associés à une zone de transition biogéographique : exemple de l'algue brune Lessonia nigrescens
    2017
    Co-Authors: Florence Tellier
    Abstract:

    Le travail réalisé au cours de cette thèse s'intègre dans la problématique générale de l'étude des processus de spéciation, en prenant comme espèces modèles de grandes algues brunes marines (Ordre des Laminariales, appelées " kelps "). Ces algues forment de véritables forêts dans les eaux tempérées froides et ont une importance économique, pour l'industrie des alginates et pour la récolte d'invertébrés marins vivant dans ces forêts. Malgré leur importance écologique et économique, et leur grande diversité en nombre d'espèces dans certaines régions du monde, les mécanismes favorisant la spéciation et contribuant à l'isolement reproducteur ont été très peu étudiés chez ces espèces. Mon travail de thèse a permis de mettre en évidence l'existence de deux espèces cryptiques au sein du complexe " Lessonia nigrescens " le long des côtes chiliennes. Je me suis tout d'abord attachée à comprendre l'histoire des deux taxa, et à discuter les différentes hypothèses à l'origine de cette spéciation. Ensuite, je me suis intéressée aux mécanismes qui permettent actuellement le maintien de l'intégrité des espèces cryptiques de L. nigrescens, en particulier dans la région de contact entre leurs aires de distribution.

  • species separation within the Lessonia nigrescens complex phaeophyceae laminariales is mirrored by ecophysiological traits
    Botanica Marina, 2015
    Co-Authors: Kristina Koch, Florence Tellier, Fadia Tala, Martin Thiel, Wilhelm Hagen, Martin Graeve, Philipp Laeseke, Kai Bischof
    Abstract:

    Lessonia nigrescens used to be an abundant kelp species along the Chilean coast, but recent molecular studies revealed the existence of a L. nigrescens species complex, which includes the two cryptic species Lessonia berteroana and Lessonia spicata. Since these species have different distributions (16°S-30°S for L. berteroana and 29°S-42°S for L. spicata), they experience differences in environmental conditions, such as solar irradiance, seawater temperature and air exposure during low tide. This study tested to what extent the genetic distinctness of each of the two species (identified by a mitochondrial marker (atp8/trnS)) is reflected by ecophysiological traits (total lipids, fatty acid composition, phlorotannins, pig- ments and variable chlorophyll a fluorescence of PSII) in response to the respective environmental conditions, prevailing along the latitudinal gradient. We studied algal individuals from eight populations (27°S-32°S, including the species overlapping zone). Phlorotannins, pigments and Chl a fluorescence of PSII were most crucial for species-specific adaptations at the respective growth sites, whereas changes in total lipids and fatty acid com- positions were negligible. Hence, species differentiation within the L. nigrescens complex is also manifested at the ecophysiological level. These findings may help to predict kelp responses towards future environmental changes.

  • Temperature Effects on Gametophyte Life-History Traits and Geographic Distribution of Two Cryptic Kelp Species
    PLOS ONE, 2012
    Co-Authors: Luz Valeria Oppliger, Florence Tellier, Sylvain Faugeron, Myriam Valero, Juan A. Correa, Aschwin H. Engelen, Vasco M. N. C. S. Vieira, Gonzalo Cifuentes Gómez, Christophe Destombe
    Abstract:

    A major determinant of the geographic distribution of a species is expected to be its physiological response to changing abiotic variables over its range. The range of a species often corresponds to the geographic extent of temperature regimes the organism can physiologically tolerate. Many species have very distinct life history stages that may exhibit different responses to environmental factors. In this study we emphasized the critical role of the haploid microscopic stage (gametophyte) of the life cycle to explain the difference of edge distribution of two related kelp species. Lessonia nigrescens was recently identified as two cryptic species occurring in parapatry along the Chilean coast: one located north and the other south of a biogeographic boundary at latitude 29–30°S. Six life history traits from microscopic stages were identified and estimated under five treatments of temperature in eight locations distributed along the Chilean coast in order to (1) estimate the role of temperature in the present distribution of the two cryptic L. nigrescens species, (2) compare marginal populations to central populations of the two cryptic species. In addition, we created a periodic matrix model to estimate the population growth rate (λ) at the five temperature treatments. Differential tolerance to temperature was demonstrated between the two species, with the gametophytes of the Northern species being more tolerant to higher temperatures than gametophytes from the south. Second, the two species exhibited different life history strategies with a shorter haploid phase in the Northern species contrasted with considerable vegetative growth in the Southern species haploid stage. These results provide strong ecological evidence for the differentiation process of the two cryptic species and show local adaptation of the life cycle at the range limits of the distribution. Ecological and evolutionary implications of these findings are discussed.

  • the Lessonia nigrescens species complex laminariales phaeophyceae shows strict parapatry and complete reproductive isolation in a secondary contact zone 1
    Journal of Phycology, 2011
    Co-Authors: Florence Tellier, Sylvain Faugeron, Javier Tapia, Christophe Destombe, Myriam Valero
    Abstract:

    During secondary contact between phylogenetically closely related species (sibling species) having diverged in allopatry, the maintenance of species integrity depends on intrinsic and extrinsic reproductive barriers. In kelps (Phaeophyceae), the observations of hybrids in laboratory conditions suggest that reproductive isolation is incomplete. However, not all interspecific crosses are successful, and very few hybrids have been observed in nature, despite the co-occurrence of many kelp species in sympatry. This suggests that there are reproductive barriers that maintain species integrity. In this study, we characterized the fine genetic structure of a secondary contact zone to clarify the extent of reproductive isolation between two sister species. In Lessonia nigrescens Bory (Laminariales, Phaeophyta) species complex, two cryptic species have been recently found out from gene phylogenies, and--waiting for a formal taxonomic description--we used their geographic distribution to name them (northern and southern species). We studied 12 populations, distributed along 50 km of coastline, and employed two molecular approaches, assigning individuals to phylogenetic species according to a diagnostic mitochondrial marker (351 individuals analyzed) and quantifying interspecific gene flow with four microsatellite markers (248 individuals analyzed). No hybridization or introgression was revealed, indicating complete reproductive isolation in natural conditions. Unexpectedly, our study demonstrated that the two species were strictly segregated in space. This absence of co-occurrence along the contact zone can partially explain the lack of hybridization, raising new interesting questions as to the mechanisms that limit sympatry at small spatial scales.

  • sex ratio variation in the Lessonia nigrescens complex laminariales phaeophyceae effect of latitude temperature and marginality 1
    Journal of Phycology, 2011
    Co-Authors: Luz Valeria Oppliger, Florence Tellier, Jessica Beltran, Sylvain Faugeron, Myriam Valero, Juan A. Correa, Christophe Destombe
    Abstract:

    : Little 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°-30° 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°C than at 10°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).

Juan A. Correa - One of the best experts on this subject based on the ideXlab platform.

  • comparative analysis of peroxiredoxin activation in the brown macroalgae scytosiphon gracilis and Lessonia nigrescens phaeophyceae under copper stress
    Physiologia Plantarum, 2013
    Co-Authors: Juan A. Correa, Carlos Lovazzano, Carolina Serrano, Loretto Contrerasporcia
    Abstract:

    : Among thiol-dependent peroxidases (TDPs) peroxiredoxins (PRXs) standout, since they are enzymes capable of reducing hydrogen peroxide, alkylhydroperoxides and peroxynitrite, and have been detected in a proteomic study of the copper-tolerant species Scytosiphon gracilis. In order to determine the importance of these enzymes in copper-stress tolerance, TDP activity and type II peroxiredoxin (II PRX) protein expression were compared between the opportunistic S. gracilis and the brown kelp Lessonia nigrescens, a species absent from copper-impacted sites due to insufficient copper-tolerance mechanisms. Individuals of both species were cultured with increasing copper concentrations (0-300 µg l(-1) Cu) for 96 h and TDP activity and lipoperoxides (LPXs) were determined together with II PRX expression by immunofluorescence and Western blot analysis. The results showed that TDP activity was higher in S. gracilis than L. nigrescens in all copper concentrations, independent of the reducing agent used (dithiothreitol, thioredoxin or glutaredoxin). This activity was copper inhibited in L. nigrescens at lower copper concentrations (20 µg l(-1) Cu) compared to S. gracilis (100 µg l(-1) Cu). The loss of activity coincided in both species with an increase in LPX, which suggests that TDP may control LPX production. Moreover, II PRX protein levels increased under copper stress only in S. gracilis. These results suggest that in S. gracilis TDP, particularly type II peroxiredoxin (II PRX), acts as an active antioxidant barrier attenuating the LPX levels generated by copper, which is not the case in L. nigrescens. Thus, from an ecological point of view these results help explaining the inability of L. nigrescens to flourish in copper-enriched environments.

  • identification of cryptic species in the Lessonia nigrescens complex phaeophyceae laminariales 1
    Journal of Phycology, 2012
    Co-Authors: Alejandra V. González, Jessica Beltran, Luciano Hiriartbertrand, Bruno De Reviers, Juan A. Correa, Verónica Flores, Bernabe Santelices
    Abstract:

    The kelp Lessonia nigrescens Bory is the most ecologically and economically important seaweed in rocky intertidal and shallow subtidal habitats along the temperate Pacific South American coasts. Recent molecular studies suggest the existence of two lineages, one (northern lineage) from 17° S to 30° S and a second (central lineage) from 29° S to 41° S. To identify and name these lineages we performed morphological, nomenclatural and field studies. Four external and three internal anatomical traits permitted a morphological separation of the two lineages. The internal structure of both lineages was different from the isolectotype of Lessonia nigrescens. It is therefore concluded that the name Lessonia nigrescens should not be used for the Chilean material. Chordaria spicata Suhr appears as the oldest available name for the central lineage, while Lessonia berteroana Montagne is the oldest name for the northern lineage. In both cases, the type material consisted of small-sized, apical branches of larger plants. The new combination Lessonia spicata (Suhr) Santelices is proposed for the central lineage and we reinstate Lessonia berteroana for the northern lineage. Laminaria scissa Suhr is reduced to synonym of L. spicata. Representative specimens of Lessonia nigrescens were not found during new visits to its type locality in Cape Horn and along Chile. Future studies should verify the status of this species.

  • Temperature Effects on Gametophyte Life-History Traits and Geographic Distribution of Two Cryptic Kelp Species
    PLOS ONE, 2012
    Co-Authors: Luz Valeria Oppliger, Florence Tellier, Sylvain Faugeron, Myriam Valero, Juan A. Correa, Aschwin H. Engelen, Vasco M. N. C. S. Vieira, Gonzalo Cifuentes Gómez, Christophe Destombe
    Abstract:

    A major determinant of the geographic distribution of a species is expected to be its physiological response to changing abiotic variables over its range. The range of a species often corresponds to the geographic extent of temperature regimes the organism can physiologically tolerate. Many species have very distinct life history stages that may exhibit different responses to environmental factors. In this study we emphasized the critical role of the haploid microscopic stage (gametophyte) of the life cycle to explain the difference of edge distribution of two related kelp species. Lessonia nigrescens was recently identified as two cryptic species occurring in parapatry along the Chilean coast: one located north and the other south of a biogeographic boundary at latitude 29–30°S. Six life history traits from microscopic stages were identified and estimated under five treatments of temperature in eight locations distributed along the Chilean coast in order to (1) estimate the role of temperature in the present distribution of the two cryptic L. nigrescens species, (2) compare marginal populations to central populations of the two cryptic species. In addition, we created a periodic matrix model to estimate the population growth rate (λ) at the five temperature treatments. Differential tolerance to temperature was demonstrated between the two species, with the gametophytes of the Northern species being more tolerant to higher temperatures than gametophytes from the south. Second, the two species exhibited different life history strategies with a shorter haploid phase in the Northern species contrasted with considerable vegetative growth in the Southern species haploid stage. These results provide strong ecological evidence for the differentiation process of the two cryptic species and show local adaptation of the life cycle at the range limits of the distribution. Ecological and evolutionary implications of these findings are discussed.

  • Seaweeds early development: detrimental effects of desiccation and attenuation by algal extracts
    Planta, 2011
    Co-Authors: Loretto Contreras-porcia, Daniela Thomas, Sebastián Callejas, Camille Sordet, Georg Pohnert, Aníbal Contreras, Ana Lafuente, María Rosa Flores-molina, Juan A. Correa
    Abstract:

    The effects of desiccation on the early development stages of Mazzaella laminarioides, Scytosiphon lomentaria and Lessonia nigrescens, algal species with different patterns of distribution across the intertidal zone, were examined in the laboratory. In addition, the protective effect against desiccation was evaluated using algal extracts, including those from Porphyra columbina, a macroalga tolerant to desiccation that lives in the uppermost part of the intertidal zone. Our results showed that M. laminarioides displayed the highest resistance to daily desiccation, followed by S. lomentaria, whereas L. nigrescens was the most susceptible. Spores from L. nigrescens exposed to desiccation, although being able to germinate, ceased further post-germination development. In addition, our results showed that all species exposed to extracts from desiccated P. columbina successfully completed their development and strongly suggest the occurrence of compounds with protective properties that help in attenuating the stress caused by desiccation. Finally, our results indicate that the magnitude of the effects generated by desiccation on the early algal development is related to the position of the species in the intertidal zone, and that the protective effects of P. columbina extracts reveal an exceptional metabolism of this species under desiccation stress.

  • sex ratio variation in the Lessonia nigrescens complex laminariales phaeophyceae effect of latitude temperature and marginality 1
    Journal of Phycology, 2011
    Co-Authors: Luz Valeria Oppliger, Florence Tellier, Jessica Beltran, Sylvain Faugeron, Myriam Valero, Juan A. Correa, Christophe Destombe
    Abstract:

    : Little 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°-30° 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°C than at 10°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).

Myriam Valero - One of the best experts on this subject based on the ideXlab platform.

  • Temperature Effects on Gametophyte Life-History Traits and Geographic Distribution of Two Cryptic Kelp Species
    PLOS ONE, 2012
    Co-Authors: Luz Valeria Oppliger, Florence Tellier, Sylvain Faugeron, Myriam Valero, Juan A. Correa, Aschwin H. Engelen, Vasco M. N. C. S. Vieira, Gonzalo Cifuentes Gómez, Christophe Destombe
    Abstract:

    A major determinant of the geographic distribution of a species is expected to be its physiological response to changing abiotic variables over its range. The range of a species often corresponds to the geographic extent of temperature regimes the organism can physiologically tolerate. Many species have very distinct life history stages that may exhibit different responses to environmental factors. In this study we emphasized the critical role of the haploid microscopic stage (gametophyte) of the life cycle to explain the difference of edge distribution of two related kelp species. Lessonia nigrescens was recently identified as two cryptic species occurring in parapatry along the Chilean coast: one located north and the other south of a biogeographic boundary at latitude 29–30°S. Six life history traits from microscopic stages were identified and estimated under five treatments of temperature in eight locations distributed along the Chilean coast in order to (1) estimate the role of temperature in the present distribution of the two cryptic L. nigrescens species, (2) compare marginal populations to central populations of the two cryptic species. In addition, we created a periodic matrix model to estimate the population growth rate (λ) at the five temperature treatments. Differential tolerance to temperature was demonstrated between the two species, with the gametophytes of the Northern species being more tolerant to higher temperatures than gametophytes from the south. Second, the two species exhibited different life history strategies with a shorter haploid phase in the Northern species contrasted with considerable vegetative growth in the Southern species haploid stage. These results provide strong ecological evidence for the differentiation process of the two cryptic species and show local adaptation of the life cycle at the range limits of the distribution. Ecological and evolutionary implications of these findings are discussed.

  • Biological and Social Aspects of kelp sustainability
    2011
    Co-Authors: Katia Frangoudes, Myriam Valero
    Abstract:

    This special issue contain 15 papers which include: the possible role of a mitochondrial genome rearrangement in maintaining the spatial segregation of 2 cryptic species of the Lessonia nigrescens species complex; male gametophyte fragmentation in Laminaria digitata; temperature effects on the microscopic haploid stage development of Laminaria ochroleuca and Sacchoriza polyschides; in situ photosynthetic performance of Laminaria digitata; trophic and biotic interactions in Laminaria digitata; expploring possible links behind the decline of the Laminaria digitata in brittany, France; microscopic stages of Laminaria ochroleuca in tide pools in northern Portugal; spatial and temporal patterns of recovery of low intertidal Laminaria digitata; the importance of having 2 species in kelp management; using genetic tools for sustainable management of kelps; mosaic genetic structure and sustainable establishment of the invasive kelp Undaria pinnatifida; management of kelp ecosystem in Japan; kelp harvesting fleet dynamics; seaweeds fisheries management in France, Japan, Chile, and Norway.

  • the Lessonia nigrescens species complex laminariales phaeophyceae shows strict parapatry and complete reproductive isolation in a secondary contact zone 1
    Journal of Phycology, 2011
    Co-Authors: Florence Tellier, Sylvain Faugeron, Javier Tapia, Christophe Destombe, Myriam Valero
    Abstract:

    During secondary contact between phylogenetically closely related species (sibling species) having diverged in allopatry, the maintenance of species integrity depends on intrinsic and extrinsic reproductive barriers. In kelps (Phaeophyceae), the observations of hybrids in laboratory conditions suggest that reproductive isolation is incomplete. However, not all interspecific crosses are successful, and very few hybrids have been observed in nature, despite the co-occurrence of many kelp species in sympatry. This suggests that there are reproductive barriers that maintain species integrity. In this study, we characterized the fine genetic structure of a secondary contact zone to clarify the extent of reproductive isolation between two sister species. In Lessonia nigrescens Bory (Laminariales, Phaeophyta) species complex, two cryptic species have been recently found out from gene phylogenies, and--waiting for a formal taxonomic description--we used their geographic distribution to name them (northern and southern species). We studied 12 populations, distributed along 50 km of coastline, and employed two molecular approaches, assigning individuals to phylogenetic species according to a diagnostic mitochondrial marker (351 individuals analyzed) and quantifying interspecific gene flow with four microsatellite markers (248 individuals analyzed). No hybridization or introgression was revealed, indicating complete reproductive isolation in natural conditions. Unexpectedly, our study demonstrated that the two species were strictly segregated in space. This absence of co-occurrence along the contact zone can partially explain the lack of hybridization, raising new interesting questions as to the mechanisms that limit sympatry at small spatial scales.

  • sex ratio variation in the Lessonia nigrescens complex laminariales phaeophyceae effect of latitude temperature and marginality 1
    Journal of Phycology, 2011
    Co-Authors: Luz Valeria Oppliger, Florence Tellier, Jessica Beltran, Sylvain Faugeron, Myriam Valero, Juan A. Correa, Christophe Destombe
    Abstract:

    : Little 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°-30° 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°C than at 10°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).

  • phylogeographic 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
    Molecular Phylogenetics and Evolution, 2009
    Co-Authors: Florence Tellier, Sylvain Faugeron, Andres P Meynard, Myriam Valero, Juan A. Correa
    Abstract:

    Abstract Phylogeographic 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°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°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.

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  • Interactive effects of UV radiation and enhanced temperature on photosynthesis, phlorotannin induction and antioxidant activities of two sub-Antarctic brown algae
    Marine Biology, 2013
    Co-Authors: Edgardo Cruces, Pirjo Huovinen, Iván Gómez
    Abstract:

    Lessonia nigrescens and Durvillaea antarctica, two large sub-Antarctic brown algae from the southern Chilean coast, were exposed to solar UV radiation in an outdoor system during a summer day (for 11 h) as well as to artificial UV radiation under controlled laboratory conditions at two temperatures (15 and 20 °C) for 72 h. Chlorophyll a fluorescence–based photoinhibition of photosynthesis was measured during the outdoor exposure, while electron transport rates, lipid peroxidation, antioxidant activity and content of phlorotannins were determined at different time intervals during the laboratory exposure. Under natural solar irradiances in summer, both species displayed well-developed dynamic photoinhibition: F _v/ F _m values decreased by 70 % at noon coinciding with the levels of PAR >1,500 μmol m^−2 s^−1 and UV-B radiation >1 W m^−2 and recovered substantially in the afternoon. In treatments including UV radiation, recovery in D. antarctica started already during the highest irradiances at noon. The results from laboratory exposures revealed that (a) elevated temperature of 20 °C exacerbated the detrimental effects of UV radiation on photochemical parameters ( F _v/ F _m and ETR); (b) peroxidative damage measured as MDA formation occurred rapidly and was strongly correlated with the decrease in F _v/ F _m, especially at elevated temperature of 20 °C; (c) the antioxidant activity and increases in soluble phlorotannins were positively correlated mainly in response to UV radiation; (d) phlorotannins were rapidly induced but strongly impaired at 20 °C. In general, short-term (2–6 h) exposures to enhanced UV radiation and temperature were effective to activate the photochemical and biochemical defenses against oxidative stress, and they continued operative during 72 h, a time span clearly exceeding the tidal or diurnal period. Furthermore, when algae were exposed to dim light and control temperature of 15 °C for 6 h, F _v/ F _m increased and lipid peroxidation decreased, indicating consistently that algae retained their ability for recovery. D. antarctica was the most sensitive species to elevated temperature for prolonged periods in the laboratory. Although no conclusive evidence for the effect of the buoyancy of fronds was found, the interspecific discrepancies in thermo-sensitivity in the UV responses found in this study are consistent with various ecological and biogeographical differences described for these species.

  • induction of phlorotannins during uv exposure mitigates inhibition of photosynthesis and dna damage in the kelp Lessonia nigrescens
    Photochemistry and Photobiology, 2010
    Co-Authors: Iván Gómez, Pirjo Huovinen
    Abstract:

    Phlorotannins of brown algae are multifunctional compounds with putative roles in herbivore deterrence, antioxidation and as primary cell wall components. Due to their peripheral localization and absorption at short wavelengths, a photoprotective role is suggested. We examined the induction of phlorotannins by artificial UV radiation in the intertidal kelp Lessonia nigrescens and whether they attenuate the inhibition of photosynthesis and DNA damage, two major detrimental effects of UV. The soluble and cell wall-bound fractions of phlorotannins were quantified in blades collected in summer and winter. Major findings were that (1) the synthesis of phlorotannins (both forms) was induced by UV only in summer; (2) the induction was fast (within 3 days); and (3) there was a positive relationship between of the contents of insoluble phlorotannins and the suppression of photoinhibition and DNA damage, measured as formation of cyclobutane pyrimidine dimers and 6-4 photoproducts. Overall, the photoprotective role of phlorotannins appears to respond to an interplay between the external UV stimulus, seasonal acclimation and intrinsic morpho-functional processes. In summer, when algae are naturally exposed to high UV irradiances, soluble phlorotannins are induced, while their transition to insoluble phlorotannins could be related with the growth requirements, as active blade elongation occurs during this season.

  • Interacting effects of copper, nitrogen and ultraviolet radiation on the physiology of three south Pacific kelps
    Marine and Freshwater Research, 2010
    Co-Authors: Pirjo Huovinen, Pablo P. Leal, Iván Gómez
    Abstract:

    Coastal ecosystems currently face multiple environmental impacts, such as nutrient loading, chemical contamination and enhanced ultraviolet (UV) radiation. Large kelps dominate many rocky shores worldwide and their capacity to handle environmental stress could have major consequences for these systems. The impacts of the interaction of copper (150 μg L–1), nitrate (350 μM) and short-term UV radiation on the physiological responses (photosynthetic activity, contents and anti-oxidant activity of phlorotannins) of three large kelps, Macrocystis pyrifera, Lessonia nigrescens and Durvillaea antarctica, from the coast of Chile were studied during a 2-week laboratory exposure. Macrocystis accumulated the most copper in its tissues, which decreased under nitrate-enriched conditions. Inhibition of photosynthetic activity by copper was observed in all three species (11–30%) after 12 days of incubation, with the strongest response in Lessonia. Nitrate enrichment mitigated the inhibitory effect of copper on photosynthesis in all three species. Soluble phlorotannin content decreased under copper and/or nitrate-enriched conditions with additional short-term UV exposure, particularly in Durvillaea, in which the strongest increase in the anti-oxidant activity of soluble phlorotannins was observed. Overall, the observed physiological responses reflect differences in morpho-functional processes and habitat characteristics of the three kelps and the importance of the interactions of multiple environmental factors.

  • Induction of phlorotannins during UV exposure mitigates inhibition of photosynthesis and DNA damage in the kelp Lessonia nigrescens
    Photochemistry and Photobiology, 2010
    Co-Authors: Iván Gómez, Pirjo Huovinen
    Abstract:

    Phlorotannins of brown algae are multifunctional compounds with putative roles in herbivore deterrence, antioxidation and as primary cell wall components. Due to their peripheral localization and absorption at short wavelengths, a photoprotective role is suggested. We examined the induction of phlorotannins by artificial UV radiation in the intertidal kelp Lessonia nigrescens and whether they attenuate the inhibition of photosynthesis and DNA damage, two major detrimental effects of UV. The soluble and cell wall-bound fractions of phlorotannins were quantified in blades collected in summer and winter. Major findings were that (1) the synthesis of phlorotannins (both forms) was induced by UV only in summer; (2) the induction was fast (within 3 days); and (3) there was a positive relationship between of the contents of insoluble phlorotannins and the suppression of photoinhibition and DNA damage, measured as formation of cyclobutane pyrimidine dimers and 6-4 photoproducts. Overall, the photoprotective role of phlorotannins appears to respond to an interplay between the external UV stimulus, seasonal acclimation and intrinsic morpho-functional processes. In summer, when algae are naturally exposed to high UV irradiances, soluble phlorotannins are induced, while their transition to insoluble phlorotannins could be related with the growth requirements, as active blade elongation occurs during this season. © 2010 The Authors. Journal Compilation. The American Society of Photobiology.

  • morpho functional patterns of photosynthesis in the south pacific kelp Lessonia nigrescens effects of uv radiation on 14c fixation and primary photochemical reactions1
    Journal of Phycology, 2007
    Co-Authors: Iván Gómez, Marcela Orostegui, Pirjo Huovinen
    Abstract:

    The morpho-functional patterns of photosynthesis, measured as 14C-fixation and chl fluorescence of PSII, also as affected by different doses of UV radiation in the laboratory were examined in the South Pacific kelp Lessonia nigrescens Bory of the coast of Valdivia, Chile (40°S). The results indicated the existence of longitudinal thallus profiles in physiological performance. In general, blades exhibited higher rates of carbon fixation and pigmentation as compared with stipes and holdfasts. Light-independent 14C fixation (LICF) was high in meristematic zones of the blades (3.5 μmol 14C·g−1 fresh weight [FW]·h−1), representing 2%–16% (percentage ratio) of the photosynthetic 14C fixation (20 μmol 14C·g−1 FW·h−1). Exposures to UV radiation indicated that biologically effective UV-B doses (BEDphotoinhibition300) of 200–400 kJ·m−2 (corresponding to current daily doses measured in Valdivia on cloudless summer days) inhibit photosynthetic 14C fixation of blades by 90%, while LICF was reduced by 70%. The percentage ratio of LICF to photosynthetic 14C fixation increased under UV exposure to 45%. Primary light reactions measured as maximum quantum yield (Fv/Fm) and electron transport rate (ETR) indicated a higher UV susceptibility of blades as compared with stipes and holdfasts: after a 48 h exposure to UV-B, the decrease in the blades was close to 30%, while in the stipes and holdfasts it was <20%. The existence of translocation of labeled carbon along the blades suggests that growth at the meristem may be powered by nonphotosynthetic processes. A possible functional role of LIFC, such as during reduction of photosynthetic carbon fixation due to enhanced UV radiation, is discussed. These results in general support the idea that the UV-related responses in Lessonia are integrated in the suite of morpho-functional adaptations of the alga.