We analyze patterns of genetic microdifferentiation within a natural population of Lathyrus sylve... more We analyze patterns of genetic microdifferentiation within a natural population of Lathyrus sylvestris, a perennial herb with both sexual reproduction and clonal growth. In a population from the northern foothills of the Pyrénées in southwestern France, a combined demographic and genetic investigation enabled the study not only of spatial genetic structure of the population, but also of the history of the population's spatial genetic structure over time. Excavation of all individuals allowed identification of clonemates. Age of each individual was determined by counting annual growth rings in the taproot, a method tested with individuals of known age planted in experimental gardens. Each individual was mapped, and genotypes of all individuals were determined using allozyme markers for a number of polymorphic loci. Distribution patterns and spatial genetic structure, both for all individuals and for different age classes, were analyzed using spatial autocorrelation statistics (Geary's Index, Moran's Index). Patterns of gene flow within the population were also studied using F-statistics and tests for random associations of alleles. Because age, allele frequencies, and location were known for each individual, it was possible to study how spatial genetic structure changed over time. Results from all these diverse approaches are consistent with one another, and clearly show the following: (1) founder effects, with the study transect being first colonized by individuals at either end of the transect that were homozygous for different alleles at one marker locus; (2) a difference in spatial distribution of individuals originated from sexual reproduction (seedlings) and from clonal growth (connected individuals); (3) restricted gene flow, due to inbreeding among related, clumped individuals; and (4) increase in heterozygote deficit within the youngest cohort of individuals. The results indicate that genetic differentiation in time was much less marked than differentiation in space. Nevertheless, the results revealed that the studied population is experiencing demographic and genetic variation in time, suggesting that it is not at equilibrium. On the one hand, spatial structuring is becoming less marked due to the recombination of founder genotypes; on the other hand, as establishment of new individuals increases, a new spatial structure emerges due to mating between relatives.
Worldwide, kelp populations are stressed by warming, increased storms and other anthropogenic dis... more Worldwide, kelp populations are stressed by warming, increased storms and other anthropogenic disturbances. Marine population distributions are projected to retreat poleward with climate change if they cannot adapt to changing conditions, which would potentially lead to a regime shift in subtidal habitats. In Northern Europe, Laminaria hyperborea is a subtidal ecosystem engineer whose distribution has shifted over millennia, leaving predicted areas of high genetic diversity from the last glacial maximum (LGM) near its southern distribution limit in the Iberian Peninsula. In Ireland, L. hyperborea structures communities by supporting diverse faunal assemblages and producing large quantities of organic carbon throughout the year. We investigated the genetic diversity of eight populations, ranging from the southern coast to the northwest of Ireland, using nine microsatellite loci. Diversity was found to be highest in Lough Hyne, a Special Area of Conservation (SAC), near the predicted climate refugium. We found evidence of isolation by distance, with high connectivity between populations that were geographically close, probably driven by short range dispersal of L. hyperborea propagules. Genetic diversity (measured as expected heterozygosity and allelic richness) was highest at Lough Hyne, and decreased northwards, as predicted from past range shifts. Expected heterozygosity was highest at Lough Hyne (0.706) and decreased northward, with the lowest value at Bridges of Ross (0.283). Based on these patterns, further fine-scale investigation into population diversity, dispersal and potential resilience in Irish kelp forests are necessary as warming and non-native species are observed more and more frequently.
Development and characterization of microsatellite markers in two agarophyte species Gracilaria b... more Development and characterization of microsatellite markers in two agarophyte species Gracilaria birdiae and G. caudata (Gracilariaceae, Rhodophyta) using next-generation sequencing
Partial clonality, mode of reproduction, heterozygote excess, population genomics, kelp The devel... more Partial clonality, mode of reproduction, heterozygote excess, population genomics, kelp The development of population genomic approaches in non-model species allows for renewed studies of the impact of reproductive systems and genetic drift on population diversity. Here, we investigate the genomic signatures of partial clonality in the deep water kelp Laminaria rodriguezii, known to reproduce by both sexual and asexual means. We compared these results with the species Laminaria digitata, a closely related species that differs by different traits, in particular its reproductive mode (no clonal reproduction). We analysed genome-wide variation with dd-RAD sequencing using 4077 SNPs in L. rodriguezii and 7364 SNPs in L. digitata. As predicted for partially clonal populations, we show that the distribution of FIS within populations of L. rodriguezii is shifted toward negative values, with a high number of loci showing heterozygote excess. This finding is the opposite of what we observed within sexual populations of L. digitata, characterized by a generalized deficit in heterozygotes. Furthermore, we observed distinct distributions of FIS among populations of L. rodriguezii, which is congruent with the predictions of theoretical models for different levels of clonality and genetic drift. These findings highlight that the empirical distribution of FIS is a promising feature for the genomic study of asexuality in natural populations. Our results also show that the populations of L. rodriguezii analysed here are genetically differentiated and probably isolated. Our study provides a conceptual framework to investigate partial clonality on the basis of RAD-sequencing SNPs. These results could be obtained without any reference genome, and are therefore of interest for various non-model species.
The coast along the temperate South East Pacific (SEP) presents a simple linear topography with a... more The coast along the temperate South East Pacific (SEP) presents a simple linear topography with a north-south orientation spanning more than 4600 km. However, environmental heterogeneity associated with two major biogeographic boundaries has been described along the SEP (30–33°S and 42°S). Recent phylogeographic studies of seaweeds revealed the existence of different cryptic species along the SEP coast and that most of the genetic breaks between them are broadly congruent with the biogeographic boundaries. These phylogeographic patterns characterized by genetic discontinuities could be attributed to historical vicariance or to budding speciation. For SEP seaweeds, two major phylogeographic patterns are observed. Endemic species living north of 42°S show complex haplotype networks and an almost complete genetic isolation between populations located only a few kilometres from each other. This extreme genetic patchiness has been related to the combined effects of limited dispersal, reduced population size and high population turnover of these intertidal seaweeds due to stochastic effects of climatic and tectonic catastrophes. On the other hand, species with a range distribution limited to the south of 42°S and inhabiting the area highly affected by the coastal ice cap during the Last Glacial Maximum (LGM), show typical signatures of post-glacial demographic expansion. Finally, molecular studies reveal that several species are recent immigrants from New Zealand, demonstrating the importance of oceanic dispersal in shaping the diversity of the SEP.
The history of a domesticated marine macroalga is studied using archaeological, phylogeographic a... more The history of a domesticated marine macroalga is studied using archaeological, phylogeographic and population genetic tools. Phylogeographic and population genetic analyses demonstrated that the cultivated red alga Gracilaria chilensis colonised the Chilean coast from New Zealand. Combining archaeological observations with phylogeographic data provided evidence that exchanges between New Zealand and Chile have occurred at least before the Holocene, likely at the end of the Last Glacial Maximum (LGM) and we suggest that migration probably occurred via rafting. Furthermore, the remarkably low microsatellite diversity found in the Chilean populations compared to those in New Zealand is consistent with a recent genetic bottleneck as a result of over-exploitation of natural populations and/or the process of domestication. Therefore, the aquaculture of this seaweed, based essentially on clonal propagation, is occurring from genetically depressed populations and may be driving the species to an extinction vortex in Chile.
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Contrasting genetic diversity patterns in two sister kelp species co-distributed along the coast of Brittany, France
Comparative sequence data from the rDNA ITS have proven very useful in species identification and... more Comparative sequence data from the rDNA ITS have proven very useful in species identification and identifying major biogeographic groups of Caulerpa taxifolia. However, the low variability of the sequence, and the need to screen hundreds of samples has limited its utility for population level studies. Here we report on the performance of two new markers suitable for population level screening: the chloroplast rDNA 16S intron‐2 and intersimple‐sequence‐repeat fingerprints (ISSRs). A new analysis of ITS1 insertion–deletion patterns was also conducted using all available sequences. A number of new insights have emerged. First, the invasive aquarium strain (Mediterranean, California) is clearly from Brisbane, but the Brisbane populations themselves may be the result of an introduction from Northern Australia. Second, an analysis of the new data in conjunction with an ITS1‐insertion–deletion analysis further suggests that the Mediterranean populations may be the result of not one, but two separate introductions. Third, intrapopulation genetic diversity between invasive Mediterranean and ‘native’ Australian populations revealed the occurrence of two divergent and widespread clades. The first clade grouped nontropical invasive populations with coastal inshore populations of Australia while the second clustered all offshore/oceanic populations so far studied. C. taxifolia, therefore exists as a complex of independent ecotypes that probably represent nascent species. Fourth, despite our finding of nine distinct nuclear and five distinct chloroplast profiles, strong linkage disequilibrium was found in most specimens, which indicates a predominance of asexual reproduction. However, nucleo‐cytoplasmic recombination was detected in one case, supporting hybridization both within and between populations.
This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
HAL (Le Centre pour la Communication Scientifique Directe), Jun 12, 2016
Headquartered in Westfield, Ind., AgReliant Genetics is an innovative seed company committed to d... more Headquartered in Westfield, Ind., AgReliant Genetics is an innovative seed company committed to delivering high quality seed, providing exceptional service and creating consistent customer value. Created in 2000 as a joint venture between the international seed groups KWS and Limagrain, AgReliant Genetics is ranked as one of the largest field seed companies in North America.
The long-held belief that animal-mediated pollination is absent in the sea has recently been cont... more The long-held belief that animal-mediated pollination is absent in the sea has recently been contradicted in seagrasses, motivating investigations of other marine phyla. This is particularly relevant in red algae, in which female gametes are not liberated and male gametes are not flagellated. Using experiments with the isopod Idotea balthica and the red alga Gracilaria gracilis , we demonstrate that biotic interactions dramatically increase the fertilization success of the alga through animal transport of spermatia on their body. This discovery suggests that animal-mediated fertilization could have evolved independently in terrestrial and marine environments and raises the possibility of its emergence in the sea before plants moved ashore.
Dispersal is a central process that affects population growth, gene flow, and ultimately species ... more Dispersal is a central process that affects population growth, gene flow, and ultimately species persistence. Here we investigate the extent to which gene flow occurs between fragmented populations of the deep-water brown algae Ericaria zosteroides (Turner) Greville (Sargassaceae, Fucales). These investigations were performed at different spatial scales from the bay of Marseille (western Provence) to Corsica. As dispersal of zygotes is shown to be limited over distances beyond a few meters, we used a multidisciplinary approach, based on Lagrangian modeling and population genomics to test the hypothesis that drifting of fertile parts of thallus (eggs on fertile branches), mediated by ocean currents, enable occasional gene flow between populations. Therefore we assessed the respective contribution of oceanographic connectivity, geographical isolation, and seawater temperatures to the genetic structure of this species. The genetic structure was assessed using 10,755 neutral SNPs and 12...
<p>(a) along the Chilean coasts, (b) detail of the transition zone (28–31°S). The range dis... more <p>(a) along the Chilean coasts, (b) detail of the transition zone (28–31°S). The range distribution of the Southern species is represented in grey (names in italics) and of the Northern species in black. Marginal populations are indicated by an asterisk. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039289#pone-0039289-t001" target="_blank">Table 1</a> for details.</p
To understand the thermal plasticity of a coastal foundation species across its latitudinal distr... more To understand the thermal plasticity of a coastal foundation species across its latitudinal distribution, we assess physiological responses to high temperature stress in the kelp Laminaria digitata in combination with population genetic characteristics and relate heat resilience to genetic features and phylogeography. We hypothesize that populations from Arctic and cold‐temperate locations are less heat resilient than populations from warm distributional edges. Using meristems of natural L. digitata populations from six locations ranging between Kongsfjorden, Spitsbergen (79°N), and Quiberon, France (47°N), we performed a common‐garden heat stress experiment applying 15°C to 23°C over eight days. We assessed growth, photosynthetic quantum yield, carbon and nitrogen storage, and xanthophyll pigment contents as response traits. Population connectivity and genetic diversity were analyzed with microsatellite markers. Results from the heat stress experiment suggest that the upper tempera...
The brown algae (Phaeophyceae) are a group of multicellular heterokonts that are ubiquitous in to... more The brown algae (Phaeophyceae) are a group of multicellular heterokonts that are ubiquitous in today's oceans. Large brown algae from multiple orders are the foundation to temperate coastal ecosystems globally, a role that extends into arctic and tropical regions, providing services indirectly through increased coastal productivity and habitat provisioning, and directly as a source of food and commercially important extracts. Recent multi-locus and genome-scale analyses have revolutionized our understanding of the brown algal phylogeny, providing a robust framework to test evolutionary hypotheses and interpret genomic variation across diverse brown algal lineages. Here, we review recent developments in our understanding of brown algal evolution based on modern advances in phylogenetics and functional genomics. We begin by summarizing modern phylogenetic hypotheses, illuminating the timescales over which the various brown algal orders diversified. We then discuss key insights on our understanding of brown algal life cycle variation and sexual reproduction systems derived from modern genomic techniques. We also review brown algal speciation mechanisms and the associated biogeographic patterns that have emerged globally. We conclude our review by discussing promising avenues for future research opened by genomic datasets, directions that are expected to reveal critical insights into brown algal evolution in past, present, and future oceans.
In the Northeast (NE) Atlantic, most intertidal fucoids and warm-temperate kelps show unique low-... more In the Northeast (NE) Atlantic, most intertidal fucoids and warm-temperate kelps show unique low-latitude gene pools matching long-term climatic refugia. For cold-temperate kelps data are scarcer despite their unique cultural, ecological and economic significance. Here we test whether the amphi-Atlantic range of Laminaria digitata is derived from past glacial survival (and vicariance) in both NE and Northwest (NW) Atlantic refugia (as suggested by niche modelling), or postglacial (re)colonization (as suggested by low mtDNA divergence). We screened 14 populations from across the species range for 12 microsatellite loci to identify and map major gene pools and refugia. We assessed if NW Atlantic survival was supported by unique endemic variation, and if genetic diversity and structure were, as predicted from larger hindcasted glacial ranges, higher in the NE Atlantic. Microsatellite data subdivided L. digitata into three main genetic groups matching Brittany, northern Europe and the NW Atlantic, with finer-scale sub-structuring within European clusters. The relatively diverse NE Atlantic lineages probably survived the Last Glacial Maximum along unglaciated periglacial shorelines of the Armorican and Celtic Seas (Brittany cluster) and Ireland (northern European cluster), and remain well differentiated despite their relative proximity. The unique Brittany gene pool, at the contemporary European rear edge, is projected to disappear in the near future under high greenhouse gas emission scenarios. Low allelic diversity and low endemism in the NW Atlantic are consistent with recent post-glacial colonization from Europe, challenging the long-standing hypothesis of in situ glacial survival. Confusion with Hedophyllum nigripes may have led to underestimation of regional diversity of L. digitata, but also to overestimation of its presence along putative transAtlantic migration routes. Partial incongruence between modelling and genetic-based biogeographic inferences highlights the benefits of comparing both approaches to understand how shifting climatic conditions affect marine species distributions and explain large-scale patterns of spatial genetic structure.
We analyze patterns of genetic microdifferentiation within a natural population of Lathyrus sylve... more We analyze patterns of genetic microdifferentiation within a natural population of Lathyrus sylvestris, a perennial herb with both sexual reproduction and clonal growth. In a population from the northern foothills of the Pyrénées in southwestern France, a combined demographic and genetic investigation enabled the study not only of spatial genetic structure of the population, but also of the history of the population&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s spatial genetic structure over time. Excavation of all individuals allowed identification of clonemates. Age of each individual was determined by counting annual growth rings in the taproot, a method tested with individuals of known age planted in experimental gardens. Each individual was mapped, and genotypes of all individuals were determined using allozyme markers for a number of polymorphic loci. Distribution patterns and spatial genetic structure, both for all individuals and for different age classes, were analyzed using spatial autocorrelation statistics (Geary&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s Index, Moran&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s Index). Patterns of gene flow within the population were also studied using F-statistics and tests for random associations of alleles. Because age, allele frequencies, and location were known for each individual, it was possible to study how spatial genetic structure changed over time. Results from all these diverse approaches are consistent with one another, and clearly show the following: (1) founder effects, with the study transect being first colonized by individuals at either end of the transect that were homozygous for different alleles at one marker locus; (2) a difference in spatial distribution of individuals originated from sexual reproduction (seedlings) and from clonal growth (connected individuals); (3) restricted gene flow, due to inbreeding among related, clumped individuals; and (4) increase in heterozygote deficit within the youngest cohort of individuals. The results indicate that genetic differentiation in time was much less marked than differentiation in space. Nevertheless, the results revealed that the studied population is experiencing demographic and genetic variation in time, suggesting that it is not at equilibrium. On the one hand, spatial structuring is becoming less marked due to the recombination of founder genotypes; on the other hand, as establishment of new individuals increases, a new spatial structure emerges due to mating between relatives.
Worldwide, kelp populations are stressed by warming, increased storms and other anthropogenic dis... more Worldwide, kelp populations are stressed by warming, increased storms and other anthropogenic disturbances. Marine population distributions are projected to retreat poleward with climate change if they cannot adapt to changing conditions, which would potentially lead to a regime shift in subtidal habitats. In Northern Europe, Laminaria hyperborea is a subtidal ecosystem engineer whose distribution has shifted over millennia, leaving predicted areas of high genetic diversity from the last glacial maximum (LGM) near its southern distribution limit in the Iberian Peninsula. In Ireland, L. hyperborea structures communities by supporting diverse faunal assemblages and producing large quantities of organic carbon throughout the year. We investigated the genetic diversity of eight populations, ranging from the southern coast to the northwest of Ireland, using nine microsatellite loci. Diversity was found to be highest in Lough Hyne, a Special Area of Conservation (SAC), near the predicted climate refugium. We found evidence of isolation by distance, with high connectivity between populations that were geographically close, probably driven by short range dispersal of L. hyperborea propagules. Genetic diversity (measured as expected heterozygosity and allelic richness) was highest at Lough Hyne, and decreased northwards, as predicted from past range shifts. Expected heterozygosity was highest at Lough Hyne (0.706) and decreased northward, with the lowest value at Bridges of Ross (0.283). Based on these patterns, further fine-scale investigation into population diversity, dispersal and potential resilience in Irish kelp forests are necessary as warming and non-native species are observed more and more frequently.
Development and characterization of microsatellite markers in two agarophyte species Gracilaria b... more Development and characterization of microsatellite markers in two agarophyte species Gracilaria birdiae and G. caudata (Gracilariaceae, Rhodophyta) using next-generation sequencing
Partial clonality, mode of reproduction, heterozygote excess, population genomics, kelp The devel... more Partial clonality, mode of reproduction, heterozygote excess, population genomics, kelp The development of population genomic approaches in non-model species allows for renewed studies of the impact of reproductive systems and genetic drift on population diversity. Here, we investigate the genomic signatures of partial clonality in the deep water kelp Laminaria rodriguezii, known to reproduce by both sexual and asexual means. We compared these results with the species Laminaria digitata, a closely related species that differs by different traits, in particular its reproductive mode (no clonal reproduction). We analysed genome-wide variation with dd-RAD sequencing using 4077 SNPs in L. rodriguezii and 7364 SNPs in L. digitata. As predicted for partially clonal populations, we show that the distribution of FIS within populations of L. rodriguezii is shifted toward negative values, with a high number of loci showing heterozygote excess. This finding is the opposite of what we observed within sexual populations of L. digitata, characterized by a generalized deficit in heterozygotes. Furthermore, we observed distinct distributions of FIS among populations of L. rodriguezii, which is congruent with the predictions of theoretical models for different levels of clonality and genetic drift. These findings highlight that the empirical distribution of FIS is a promising feature for the genomic study of asexuality in natural populations. Our results also show that the populations of L. rodriguezii analysed here are genetically differentiated and probably isolated. Our study provides a conceptual framework to investigate partial clonality on the basis of RAD-sequencing SNPs. These results could be obtained without any reference genome, and are therefore of interest for various non-model species.
The coast along the temperate South East Pacific (SEP) presents a simple linear topography with a... more The coast along the temperate South East Pacific (SEP) presents a simple linear topography with a north-south orientation spanning more than 4600 km. However, environmental heterogeneity associated with two major biogeographic boundaries has been described along the SEP (30–33°S and 42°S). Recent phylogeographic studies of seaweeds revealed the existence of different cryptic species along the SEP coast and that most of the genetic breaks between them are broadly congruent with the biogeographic boundaries. These phylogeographic patterns characterized by genetic discontinuities could be attributed to historical vicariance or to budding speciation. For SEP seaweeds, two major phylogeographic patterns are observed. Endemic species living north of 42°S show complex haplotype networks and an almost complete genetic isolation between populations located only a few kilometres from each other. This extreme genetic patchiness has been related to the combined effects of limited dispersal, reduced population size and high population turnover of these intertidal seaweeds due to stochastic effects of climatic and tectonic catastrophes. On the other hand, species with a range distribution limited to the south of 42°S and inhabiting the area highly affected by the coastal ice cap during the Last Glacial Maximum (LGM), show typical signatures of post-glacial demographic expansion. Finally, molecular studies reveal that several species are recent immigrants from New Zealand, demonstrating the importance of oceanic dispersal in shaping the diversity of the SEP.
The history of a domesticated marine macroalga is studied using archaeological, phylogeographic a... more The history of a domesticated marine macroalga is studied using archaeological, phylogeographic and population genetic tools. Phylogeographic and population genetic analyses demonstrated that the cultivated red alga Gracilaria chilensis colonised the Chilean coast from New Zealand. Combining archaeological observations with phylogeographic data provided evidence that exchanges between New Zealand and Chile have occurred at least before the Holocene, likely at the end of the Last Glacial Maximum (LGM) and we suggest that migration probably occurred via rafting. Furthermore, the remarkably low microsatellite diversity found in the Chilean populations compared to those in New Zealand is consistent with a recent genetic bottleneck as a result of over-exploitation of natural populations and/or the process of domestication. Therefore, the aquaculture of this seaweed, based essentially on clonal propagation, is occurring from genetically depressed populations and may be driving the species to an extinction vortex in Chile.
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Contrasting genetic diversity patterns in two sister kelp species co-distributed along the coast of Brittany, France
Comparative sequence data from the rDNA ITS have proven very useful in species identification and... more Comparative sequence data from the rDNA ITS have proven very useful in species identification and identifying major biogeographic groups of Caulerpa taxifolia. However, the low variability of the sequence, and the need to screen hundreds of samples has limited its utility for population level studies. Here we report on the performance of two new markers suitable for population level screening: the chloroplast rDNA 16S intron‐2 and intersimple‐sequence‐repeat fingerprints (ISSRs). A new analysis of ITS1 insertion–deletion patterns was also conducted using all available sequences. A number of new insights have emerged. First, the invasive aquarium strain (Mediterranean, California) is clearly from Brisbane, but the Brisbane populations themselves may be the result of an introduction from Northern Australia. Second, an analysis of the new data in conjunction with an ITS1‐insertion–deletion analysis further suggests that the Mediterranean populations may be the result of not one, but two separate introductions. Third, intrapopulation genetic diversity between invasive Mediterranean and ‘native’ Australian populations revealed the occurrence of two divergent and widespread clades. The first clade grouped nontropical invasive populations with coastal inshore populations of Australia while the second clustered all offshore/oceanic populations so far studied. C. taxifolia, therefore exists as a complex of independent ecotypes that probably represent nascent species. Fourth, despite our finding of nine distinct nuclear and five distinct chloroplast profiles, strong linkage disequilibrium was found in most specimens, which indicates a predominance of asexual reproduction. However, nucleo‐cytoplasmic recombination was detected in one case, supporting hybridization both within and between populations.
This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
HAL (Le Centre pour la Communication Scientifique Directe), Jun 12, 2016
Headquartered in Westfield, Ind., AgReliant Genetics is an innovative seed company committed to d... more Headquartered in Westfield, Ind., AgReliant Genetics is an innovative seed company committed to delivering high quality seed, providing exceptional service and creating consistent customer value. Created in 2000 as a joint venture between the international seed groups KWS and Limagrain, AgReliant Genetics is ranked as one of the largest field seed companies in North America.
The long-held belief that animal-mediated pollination is absent in the sea has recently been cont... more The long-held belief that animal-mediated pollination is absent in the sea has recently been contradicted in seagrasses, motivating investigations of other marine phyla. This is particularly relevant in red algae, in which female gametes are not liberated and male gametes are not flagellated. Using experiments with the isopod Idotea balthica and the red alga Gracilaria gracilis , we demonstrate that biotic interactions dramatically increase the fertilization success of the alga through animal transport of spermatia on their body. This discovery suggests that animal-mediated fertilization could have evolved independently in terrestrial and marine environments and raises the possibility of its emergence in the sea before plants moved ashore.
Dispersal is a central process that affects population growth, gene flow, and ultimately species ... more Dispersal is a central process that affects population growth, gene flow, and ultimately species persistence. Here we investigate the extent to which gene flow occurs between fragmented populations of the deep-water brown algae Ericaria zosteroides (Turner) Greville (Sargassaceae, Fucales). These investigations were performed at different spatial scales from the bay of Marseille (western Provence) to Corsica. As dispersal of zygotes is shown to be limited over distances beyond a few meters, we used a multidisciplinary approach, based on Lagrangian modeling and population genomics to test the hypothesis that drifting of fertile parts of thallus (eggs on fertile branches), mediated by ocean currents, enable occasional gene flow between populations. Therefore we assessed the respective contribution of oceanographic connectivity, geographical isolation, and seawater temperatures to the genetic structure of this species. The genetic structure was assessed using 10,755 neutral SNPs and 12...
<p>(a) along the Chilean coasts, (b) detail of the transition zone (28–31°S). The range dis... more <p>(a) along the Chilean coasts, (b) detail of the transition zone (28–31°S). The range distribution of the Southern species is represented in grey (names in italics) and of the Northern species in black. Marginal populations are indicated by an asterisk. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0039289#pone-0039289-t001" target="_blank">Table 1</a> for details.</p
To understand the thermal plasticity of a coastal foundation species across its latitudinal distr... more To understand the thermal plasticity of a coastal foundation species across its latitudinal distribution, we assess physiological responses to high temperature stress in the kelp Laminaria digitata in combination with population genetic characteristics and relate heat resilience to genetic features and phylogeography. We hypothesize that populations from Arctic and cold‐temperate locations are less heat resilient than populations from warm distributional edges. Using meristems of natural L. digitata populations from six locations ranging between Kongsfjorden, Spitsbergen (79°N), and Quiberon, France (47°N), we performed a common‐garden heat stress experiment applying 15°C to 23°C over eight days. We assessed growth, photosynthetic quantum yield, carbon and nitrogen storage, and xanthophyll pigment contents as response traits. Population connectivity and genetic diversity were analyzed with microsatellite markers. Results from the heat stress experiment suggest that the upper tempera...
The brown algae (Phaeophyceae) are a group of multicellular heterokonts that are ubiquitous in to... more The brown algae (Phaeophyceae) are a group of multicellular heterokonts that are ubiquitous in today's oceans. Large brown algae from multiple orders are the foundation to temperate coastal ecosystems globally, a role that extends into arctic and tropical regions, providing services indirectly through increased coastal productivity and habitat provisioning, and directly as a source of food and commercially important extracts. Recent multi-locus and genome-scale analyses have revolutionized our understanding of the brown algal phylogeny, providing a robust framework to test evolutionary hypotheses and interpret genomic variation across diverse brown algal lineages. Here, we review recent developments in our understanding of brown algal evolution based on modern advances in phylogenetics and functional genomics. We begin by summarizing modern phylogenetic hypotheses, illuminating the timescales over which the various brown algal orders diversified. We then discuss key insights on our understanding of brown algal life cycle variation and sexual reproduction systems derived from modern genomic techniques. We also review brown algal speciation mechanisms and the associated biogeographic patterns that have emerged globally. We conclude our review by discussing promising avenues for future research opened by genomic datasets, directions that are expected to reveal critical insights into brown algal evolution in past, present, and future oceans.
In the Northeast (NE) Atlantic, most intertidal fucoids and warm-temperate kelps show unique low-... more In the Northeast (NE) Atlantic, most intertidal fucoids and warm-temperate kelps show unique low-latitude gene pools matching long-term climatic refugia. For cold-temperate kelps data are scarcer despite their unique cultural, ecological and economic significance. Here we test whether the amphi-Atlantic range of Laminaria digitata is derived from past glacial survival (and vicariance) in both NE and Northwest (NW) Atlantic refugia (as suggested by niche modelling), or postglacial (re)colonization (as suggested by low mtDNA divergence). We screened 14 populations from across the species range for 12 microsatellite loci to identify and map major gene pools and refugia. We assessed if NW Atlantic survival was supported by unique endemic variation, and if genetic diversity and structure were, as predicted from larger hindcasted glacial ranges, higher in the NE Atlantic. Microsatellite data subdivided L. digitata into three main genetic groups matching Brittany, northern Europe and the NW Atlantic, with finer-scale sub-structuring within European clusters. The relatively diverse NE Atlantic lineages probably survived the Last Glacial Maximum along unglaciated periglacial shorelines of the Armorican and Celtic Seas (Brittany cluster) and Ireland (northern European cluster), and remain well differentiated despite their relative proximity. The unique Brittany gene pool, at the contemporary European rear edge, is projected to disappear in the near future under high greenhouse gas emission scenarios. Low allelic diversity and low endemism in the NW Atlantic are consistent with recent post-glacial colonization from Europe, challenging the long-standing hypothesis of in situ glacial survival. Confusion with Hedophyllum nigripes may have led to underestimation of regional diversity of L. digitata, but also to overestimation of its presence along putative transAtlantic migration routes. Partial incongruence between modelling and genetic-based biogeographic inferences highlights the benefits of comparing both approaches to understand how shifting climatic conditions affect marine species distributions and explain large-scale patterns of spatial genetic structure.
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