DSpace Angular :: Browsing by Author "Faugeron, Sylvain"

Browsing by Author "Faugeron, Sylvain"

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Aldehyde perception induces specific molecular responses in Laminaria digitata and affects algal consumption by a specialist grazer
(2023) Xing, Qikun; Cabioch, Lea; Desrut, Antoine; Le Corguille, Gildas; Rousvoal, Sylvie; Dartevelle, Laurence; Rolland, Elodie; Guitton, Yann; Potin, Philippe; Markov, Gabriel V.; Faugeron, Sylvain; Leblanc, Catherine
In the marine environment, distance signaling based on water-borne cues occurs during interactions between macroalgae and herbivores. In the brown alga Laminaria digitata from North-Atlantic Brittany, oligoalginates elicitation or grazing was shown to induce chemical and transcriptomic regulations, as well as emission of a wide range of volatile aldehydes, but their biological roles as potential defense or warning signals in response to herbivores remain unknown. In this context, bioassays using the limpet Patella pellucida and L. digitata were carried out for determining the effects of algal transient incubation with 4-hydroxyhexenal (4-HHE), 4-hydroxynonenal (4-HNE) and dodecadienal on algal consumption by grazers. Simultaneously, we have developed metabolomic and transcriptomic approaches to study algal molecular responses after treatments of L. digitata with these chemical compounds. The results indicated that, unlike the treatment of the plantlets with 4-HNE or dodecadienal, treatment with 4-HHE decreases algal consumption by herbivores at 100 ng.ml(-1). Moreover, we showed that algal metabolome was significantly modified according to the type of aldehydes, and more specifically the metabolite pathways linked to fatty acid degradation. RNAseq analysis further showed that 4-HHE at 100 ng.ml(-1) can activate the regulation of genes related to oxylipin signaling pathways and specific responses, compared to oligoalginates elicitation. As kelp beds constitute complex ecosystems consisting of habitat and food source for marine herbivores, the algal perception of specific aldehydes leading to targeted molecular regulations could have an important biological role on kelps/grazers interactions.
Assessment of local adaptation and outbreeding risks in contrasting thermal environments of the giant kelp, Macrocystis pyrifera
(2024) Solas, Maribel; Correa, Rodolfo A.; Barria, Fernanda; Garces, Cristobal; Camus, Carolina; Faugeron, Sylvain
Understanding the scope of local adaptation is critical to the definition of restoration strategies as it may affect individuals used as breeders or transplants. The assessment of such risks is, however, challenging for large seaweeds such as kelps, because their experimental manipulation is difficult in marine coastal environments. We investigated the consequences of local adaptation on reproductive traits of gametophytes, and growth and survival of sporophytes of the giant kelp, Macrocystis pyrifera. Over a thousand juvenile sporophytes were obtained from controlled crosses using 2 to 3 parental sporophytes from each of 18 populations from 5 different regions (i.e. Magellanes. Southern Chile, Atacama, Peru and California), to assess fertility and fecundity of female gametophytes when exposed to males of different habitats, and to produce juvenile sporophytes that were used to test for local adaptation sensu stricto in common garden experiments. By comparing sympatric and allopatric combinations of source populations and the average temperature of the sampled regions, we detected a significant pattern of local adaptation. We quantified the risks associated with different combinations of population/habitat for the performance of juvenile sporophytes typically used as transplants in kelp restoration actions. We found evidence of reduced reproductive success associated with outbreeding for high latitude populations, while low latitude populations favored hybrid crosses, suggesting a shift between outbreeding depression and hybrid vigor across different habitats (i.e., temperature). We also showed that a heatwave equally increased mortality of sporophytes across all regions except for Peruvian inbred crosses, suggesting these low latitude populations hold key genetic resources for future actions under ocean warming. Altogether, these experiments provide a framework for assessing risks associated with the choice of source populations in any kelp species.
Comparative phylogeography of twoAgarophytonspecies in the New Zealand archipelago
(2020) Huanel, Oscar R.; Nelson, Wendy E.; Robitzch, Vanessa; Mauger, Stéphane; Faugeron, Sylvain; Preuss, Maren; Zuccarello, Giuseppe C.; Guillemin, Marie Laure
Contrasting response of Gracilaria chilensis (Gracilariales, Rhodophyta) life cycle stages to epiphyte infection
(2023) Usandizaga, Sara; Beltran, Jessica; Faugeron, Sylvain; Camus, Carolina
The red seaweed Gracilaria chilensis, a species extensively cultivated in Chile for agar extraction, was subjected to a bioassay to determine the susceptibility of tetrasporophytes, female and male gametophytes collected from natural and cultivated populations, to the red epiphyte Acrochaetium sp. and the brown epiphyte Ectocarpus sp. The settlement, attachment and germination of epiphytic algal spores on G. chilensis thalli were evaluated, and the photosynthetic responses and the concentration of total phenolic compounds were determined as a possible response of G. chilensis to biotic stress. The results showed that when the thalli were exposed to Acrochaetium infection, female individuals had a significantly lower percentage of germinated spores than other phases of the life cycle. After infection with Ectocarpus spores, males showed the highest % germination of the epiphyte. For both epiphytes, the response of tetrasporophytes from natural and cultivated populations shows a similar trend. The total content of phenolic compounds showed that, in general, the individuals infected with Acrochaetium had a higher defense capacity, whereas the infection with the brown alga did not induce a significant release of phenolic compounds. Despite the heterogeneous results observed for photosynthetic activity, a higher photoinhibition of the maximum fluorescence quantum yield (F-v/F-m) was observed in thalli with the Acrochaetium epiphyte, confirming that G. chilensis was subjected to stress after infection. Taken together, these observations may suggest that the cultivation of females could be of long-term benefit to farms by reducing biomass losses under stressful conditions and epiphyte invasions on farms.
Development and characterization of nine polymorphic microsatellite markers in the Chilean kelp Lessonia nigrescens
(2009) Faugeron, Sylvain; Veliz, David; Peralta, Gioconda; Tapia, Javier; Tellier, Florence; Billot, Claire; Martinez, Enrique
A total of nine microsatellite loci were isolated and characterized in the Chilean kelp Lessonia nigrescens Bory. Using two different enriched libraries, we observed 1-14 alleles per locus in two samples of 21 kelp individuals each. The observed heterozygosities ranged from 0.05 to 0.80 and all loci are in Hardy-Weinberg equilibrium for one or both samples. Seventeen samples collected from different sites showed high allele diversity along the species distribution. The variation detected at these markers is currently being used for the study of populations of Lessonia nigrescens at different geographical scales.
Diversity, phenomenology and epidemiology of epiphytism in farmed Gracilaria chilensis (Rhodophyta) in northern Chile
(2006) Leonardi, Patricia I.; Miravalles, Alicia B.; Faugeron, Sylvain; Flores, Veronica; Beltran, Jessica; Correa, Juan A.
This study identified the most common epiphytes infecting the algal host Gracilaria chilensis on a farm in northern Chile. Simultaneously, the types of host-epiphyte interfaces were characterized and their relative abundance and temporal variability were monitored. Five types of anatomical relationships were detected. Infection type I included the epiphytes weakly attached to the surface of the host and not associated with damage of host tissues (i.e. Hincksia mitchelliae, H. granulosa and Ectocarpus acutus). Infection type II included those epiphytes strongly attached to the surface of the host but not associated with any host tissue damage (i.e. Acrochaetium sp., Antithamnionella sp. and Colpomenia sinuosa). Infection type III included all the epiphytes that penetrated the outer layer of the host wall without damaging its cortical cells (i.e. Xenococcus sp. and Sahlingia subintegra). Infection type IV included epiphytes penetrating deep into the host cell wall, disorganizing the cortical tissue (i. e. Ulva lactuca and Acrosorium corallinarum). Infection type V included epiphytes that penetrated deeply into the cortex, reached the medullary tissue and caused destruction of the host's cells in the area around the infection (i.e. Ceramium rubrum and Polysiphonia harveyi). Prevalence varied with time and with infection type, with types II and III reaching up to 80% and 90% of the thalli respectively. Severity of epiphyte infection was similar to the distribution of infection prevalence, with crustose epiphytes colonizing up to 80% of the host surface.
Environmental and demographic factors influence the spatial genetic structure of an intertidal barnacle in central-northern Chile
(2019) Barahona, Mario; Broitman, Bernardo R.; Faugeron, Sylvain; Jaugeon, Lucie; Ospina-Alvarez, Andres; Veliz, David; Navarrete, Sergio A.
Understanding the multiplicity of processes producing genetic patterns in natural populations can shed light on the ecology and evolution of species, and help guide effective management and conservation strategies. Here we investigated the role of environmental, demographic, and geographic factors in shaping the spatial patterns of genetic diversity and differentiation of the intertidal barnacle Notochthamalus scabrosus along the central-northern coast of Chile (28-34 degrees S). We analyzed genetic data from 7 microsatellite loci genotyped for 300 individuals sampled from 10 sites and combined this information with 8 site-specific environmental (4), demographic (2), and geographic (2) variables using least squares linear regressions, generalized linear models, and matrix regression analyses. We found a strong association between the spatially structured genetic diversity of N. scabrosus and patterns of temporal variability in chlorophyll a, and among-site differences in seawater temperature and adult abundance. Our results illustrate that population size, partly driven by recruitment success, can leave a signal on genetic structure of this highly dispersive marine species. The significant effect of temperature and chlorophyll a stresses that local adaptation may be key to understanding the spatial genetic structure of our model species. Hence, the results of this work represent an advance towards understanding the usually complex causal relationships between environmental variables, gene flow, and genetic diversity patterns of coastal populations.
Experimental transplants of the large kelp Lessonia nigrescens (Phaeophyceae) in high-energy wave exposed rocky intertidal habitats of northern Chile
(2006) Correa, Juan A.; Lagos, Nelson A.; Medina, Matias H.; Castilla, Juan C.; Cerda, Mauricio; Ramirez, Marco; Martinez, Enrique; Faugeron, Sylvain; Andrade, Santiago; Pinto, Raquel; Contreras, Loretto
Potential for addressing ecological and physiological issues becomes severely limited when the organisms required to experimentally test specific hypotheses are absent from the study areas. This report describes a simple and inexpensive device for re-planting kelps into the lower intertidal zone of wave-swept rocky habitats, using Lessonia nigrescens Bory as a model organism. The device allows a wide range of plant sizes to be anchored by the holdfast. Transplanted kelps regenerated, re-attached to the substratum and overgrew the transplanting device. These results confirm the feasibility of using this technique to tackle a variety of highly relevant questions involving ecological, physiological, conservation, restoration and management issues. (c) 2006 Elsevier B.V. All rights reserved.
First report of the intentionally introduced kelp, Saccharina japonica, in the Pacific coast of southern Chile
(2022) Camus, Carolina; Leal, Pablo P.; Faugeron, Sylvain; Henriquez-Antipa, Luis A.; Fernandez, Pamela A.; Cook, Sebastian; Carcamo, P. Francisco; Vargas, Jaime
We report for the first time the occurrence of the Japanese kelp Saccharina japonica on the Pacific coast of southern Chile following an illegal introduction for aquaculture purposes. In November 2020, a citizen complaint indicated that the non-native kelp was being illegally farmed in Canal Caicae ' n. Specimens of the non-native kelp were collected during successive surveys for molecular and morphological analyses, and reproductive viability tests. The species was determined using two mitochondrial molecular markers, COI and trnW-L. Phylogenetic analysis confirmed the taxonomic identity of the specimen as S. japonica and revealed a genetic similarity with S. japonica x S. latissima hybrid cultivars Sanhai and Rongfu. In April 2021, several adult specimens became fertile at the farm site and the laboratory and released meiospores were able to develop into embryos after 15-20 days of incubation. These findings underline the risk for this kelp to disperse and colonize in the natural surrounding habitat, with potential impacts on local coastal ecosystems.
Herbivore-induced chemical and molecular responses of the kelps Laminaria digitata and Lessonia spicata
(2017) Ritter, Andres; Cabioch, Lea; Brillet-Gueguen, Loraine; Corre, Erwan; Cosse, Audrey; Dartevelle, Laurence; Durufle, Harold; Fasshauer, Carina; Goulitquer, Sophie; Thomas, Francois; Correa, Juan A.; Potin, Philippe; Faugeron, Sylvain; Leblanc, Catherine
Kelps are founding species of temperate marine ecosystems, living in intertidal coastal areas where they are often challenged by generalist and specialist herbivores. As most sessile organisms, kelps develop defensive strategies to restrain grazing damage and preserve their own fitness during interactions with herbivores. To decipher some inducible defense and signaling mechanisms, we carried out metabolome and transcriptome analyses in two emblematic kelp species, Lessonia spicata from South Pacific coasts and Laminaria digitata from North Atlantic, when challenged with their main specialist herbivores. Mass spectrometry based metabolomics revealed large metabolic changes induced in these two brown algae following challenges with their own specialist herbivores. Targeted metabolic profiling of L. spicata further showed that free fatty acid (FFA) and amino acid (AA) metabolisms were particularly regulated under grazing. An early stress response was illustrated by the accumulation of Sulphur containing amino acids in the first twelve hours of herbivory pressure. At latter time periods (after 24 hours), we observed FFA liberation and eicosanoid oxylipins synthesis likely representing metabolites related to stress. Global transcriptomic analysis identified sets of candidate genes specifically induced by grazing in both kelps. qPCR analysis of the top candidate genes during a 48-hours time course validated the results. Most of these genes were particularly activated by herbivore challenge after 24 hours, suggesting that transcriptional reprogramming could be operated at this time period. We demonstrated the potential utility of these genes as molecular markers for herbivory by measuring their inductions in grazed individuals of field harvested L. digitata and L. spicata. By unravelling the regulation of some metabolites and genes following grazing pressure in two kelps representative of the two hemispheres, this work contributes to provide a set of herbivore-induced chemical and molecular responses in kelp species, showing similar inducible responses upon specialist herbivores in their respective ecosystems.
Mates Matter: Gametophyte Kinship Recognition and Inbreeding in the Giant Kelp, Macrocystis pyrifera (Laminariales, Phaeophyceae)
(2021) Camus, Carolina; Solas, Maribel; Martinez, Camila; Vargas, Jaime; Garces, Cristobal; Gil-Kodaka, Patricia; Ladah, Lydia B.; Serrao, Ester A.; Faugeron, Sylvain
Inbreeding, the mating between genetically related individuals, often results in reduced survival and fecundity of offspring, relative to outcrossing. Yet, high inbreeding rates are commonly observed in seaweeds, suggesting compensatory reproductive traits may affect the costs and benefits of the mating system. We experimentally manipulated inbreeding levels in controlled crossing experiments, using gametophytes from 19 populations of Macrocystis pyrifera along its Eastern Pacific coastal distribution (EPC). The objective was to investigate the effects of male-female kinship on female fecundity and fertility, to estimate inbreeding depression in the F1 progeny, and to assess the variability of these effects among different regions and habitats of the EPC. Results revealed that the presence and kinship of males had a significant effect on fecundity and fertility of female gametophytes. Females left alone or in the presence of sibling males express the highest gametophyte size, number, and size of oogonia, suggesting they were able to sense the presence and the identity of their mates before gamete contact. The opposite trend was observed for the production of embryos per female gametes, indicating higher costs of selfing and parthenogenesis than outcrossing on fertility. However, the increased fecundity compensated for the reduced fertility, leading to a stable overall reproductive output. Inbreeding also affected morphological traits of juvenile sporophytes, but not their heatwave tolerance. The male-female kinship effect was stronger in high-latitude populations, suggesting that females from low-latitude marginal populations might have evolved to mate with any male gamete to guarantee reproductive success.
Past climate-driven range shifts structuring intraspecific biodiversity levels of the giant kelp (Macrocystis pyrifera) at global scales
(2023) Assis, Jorge; Alberto, Filipe; Macaya, Erasmo C.; Coelho, Nelson Castilho; Faugeron, Sylvain; Pearson, Gareth A.; Ladah, Lydia; Reed, Daniel C.; Raimondi, Peter; Mansilla, Andres; Brickle, Paul; Zuccarello, Giuseppe C.; Serrao, Ester A.
The paradigm of past climate-driven range shifts structuring the distribution of marine intraspecific biodiversity lacks replication in biological models exposed to comparable limiting conditions in independent regions. This may lead to confounding effects unlinked to climate drivers. We aim to fill in this gap by asking whether the global distribution of intraspecific biodiversity of giant kelp (Macrocystis pyrifera) is explained by past climate changes occurring across the two hemispheres. We compared the species' population genetic diversity and structure inferred with microsatellite markers, with range shifts and long-term refugial regions predicted with species distribution modelling (SDM) from the last glacial maximum (LGM) to the present. The broad antitropical distribution of Macrocystis pyrifera is composed by six significantly differentiated genetic groups, for which current genetic diversity levels match the expectations of past climate changes. Range shifts from the LGM to the present structured low latitude refugial regions where genetic relics with higher and unique diversity were found (particularly in the Channel Islands of California and in Peru), while post-glacial expansions following similar to 40% range contraction explained extensive regions with homogenous reduced diversity. The estimated effect of past climate-driven range shifts was comparable between hemispheres, largely demonstrating that the distribution of intraspecific marine biodiversity can be structured by comparable evolutionary forces across the global ocean. Additionally, the differentiation and endemicity of regional genetic groups, confers high conservation value to these localized intraspecific biodiversity hotspots of giant kelp forests.
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?
(2009) Tellier, Florence; Meynard, Andres P.; Correa, Juan A.; Faugeron, Sylvain; Valero, Myriam
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 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.
Phylogeography of the Marine Otter (Lontra felina): Historical and Contemporary Factors Determining Its Distribution
(2010) Vianna, Juliana A.; Ayerdi, Paula; Medina-Vogel, Gonzalo; Mangel, Jeffrey C.; Zeballos, Horacio; Apaza, Manuel; Faugeron, Sylvain
The evolutionary history of a species can be revealed by phylogeographical analysis; nevertheless, not only historical but also contemporary processes can imprint on the distribution of genetic diversity. We report on the phylogeny of Lontra ssp. in South America, and the role of spatial heterogeneity in shaping the distribution and population structure of the endangered marine otter, Lontra felina. Analyzing a total of 2261 bp of mitochondrial DNA (mtDNA) revealed the recent divergence of L. felina from L. provocax. A strong population structure (Phi(st) = 0.83, P < 0.0001) and a significant pattern of isolation by distance were described for L. felina (n = 168) across a wide geographical distribution (13 degrees 53'S to 43 degrees 36'S). Lontra felina mtDNA phylogeny is composed of 2 main clades: a clade from Peru and another composed of Chilean haplotypes. Northern populations show different divergent lineages and higher genetic diversity when compared with more recently colonized southern populations. Furthermore, long sandy beaches seem to act as barriers to dispersal, creating 2 evolutionary significant units in agreement with subspecies previous description, and at least 5 different management units (MUs). At a fine spatial scale, the size of rocky seashore patches, the distance between patches and anthropogenic factors also play important roles in species gene flow.
Phylogeography of the Patagonian otter Lontra provocax: adaptive divergence to marine habitat or signature of southern glacial refugia?
(2011) Vianna, Juliana A.; Medina-Vogel, Gonzalo; Chehebar, Claudio; Sielfeld, Walter; Olavarria, Carlos; Faugeron, Sylvain
Background: A number of studies have described the extension of ice cover in western Patagonia during the Last Glacial Maximum, providing evidence of a complete cover of terrestrial habitat from 41 degrees S to 56 degrees S and two main refugia, one in south-eastern Tierra del Fuego and the other north of the Chilo, Island. However, recent evidence of high genetic diversity in Patagonian river species suggests the existence of aquatic refugia in this region. Here, we further test this hypothesis based on phylogeographic inferences from a semi-aquatic species that is a top predator of river and marine fauna, the huillin or Southern river otter (Lontra provocax).
Possible 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, Myriam
In 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.
Pre-domestication bottlenecks of the cultivated seaweed Gracilaria chilensis
(2022) Huanel, Oscar R.; Quesada-Calderon, Suany; Molina, Cristian Rios; Morales-Gonzalez, Sarai; Saenz-Agudelo, Pablo; Nelson, Wendy A.; Arakaki, Natalia; Mauger, Stephane; Faugeron, Sylvain; Guillemin, Marie-Laure
Gracilaria chilensis is the main cultivated seaweed in Chile. The low genetic diversity observed in the Chilean populations has been associated with the over-exploitation of natural beds and/or the founder effect that occurred during post-glacial colonization from New Zealand. How these processes have affected its evolutionary trajectory before farming and incipient domestication is poorly understood. In this study, we used 2232 single nucleotide polymorphisms (SNPs) to assess how the species' evolutionary history in New Zealand (its region of origin), the founder effect linked to transoceanic dispersion and colonization of South America, and the recent over-exploitation of natural populations have influenced the genetic architecture of G. chilensis in Chile. The contrasting patterns of genetic diversity and structure observed between the two main islands in New Zealand attest to the important effects of Quaternary glacial cycles on G. chilensis. Approximate Bayesian Computation (ABC) analyses indicated that Chatham Island and South America were colonized independently near the end of the Last Glacial Maximum and emphasized the importance of coastal and oceanic currents during that period. Furthermore, ABC analyses inferred the existence of a recent and strong genetic bottleneck in Chile, matching the period of over-exploitation of the natural beds during the 1970s, followed by rapid demographic expansion linked to active clonal propagation used in farming. Recurrent genetic bottlenecks strongly eroded the genetic diversity of G. chilensis prior to its cultivation, raising important challenges for the management of genetic resources in this incipiently domesticated species.
Relatedness does not predict vigilance in a population of the social rodent Octodon degus
(2013) Quirici, Veronica; Palma, Macarena; Sobrero, Raul; Faugeron, Sylvain; Ebensperger, Luis A.
The possibility that social foragers adjust and coordinate their scanning activity when in the presence of close relatives to attain inclusive fitness benefits remains controversial and scarcely examined. To this aim, we first tested the null hypothesis of no association between foraging individuals of the diurnal rodent, Octodon degus and their pairwise relatedness (six microsatellite loci), under natural conditions. Secondly, we examined the influence of relatedness on scan effort (percent overlapping) and temporal distribution of scanning using linear regression. Finally, we evaluated whether temporal distributions of scanning were significantly lower (coordination) or higher (synchrony) than random expectations using bootstrapping. We found that pairwise relatedness between focal degus and their foraging partner did not influence the scan effort or the temporal distribution of scanning. These original, field-based findings imply that vigilance behavior in socially foraging degus is unlikely to be kin-selected and adds to results from previous lab studies in that kinship remains a poor predictor of social behavior in these animals. Overall, our study adds to others revealing that kin selection may not have had an impact on aspects of social behavior such as vigilance during social foraging.
SEX 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, Christophe
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 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).
The 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, Sylvain
Natural 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.

Browsing by Author "Faugeron, Sylvain"

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