Biology subjects

Mauger, S.

Publications and source records attributed to Mauger, S..

7 recordsLinked to original sources

bioRxiv2026

Comparison of the performance of sporophytes derived from narrow and wide genetic crosses between strains of the cultivated kelp Saccharina latissima

Seaweed mariculture allows sustainable production of large quantities of biomass for multiple downstream applications but the genotypes cultivated by this industry need to be improved to increase efficiency and cost-effectiveness. It is important that the genetic improvement of cultivated strains does not lead to the introduction of foreign genetic material into wild seaweed populations, which are already under threat from global heating. To circumvent this problem, efforts are being made to develop breeding approaches based on the use of locally-resourced genetic material. The aim of this study was to evaluate the potential effectiveness of this 'local' breeding strategy compared to a classical breeding approach based on wide genetic crosses. Analyses of growth rates and cell wall composition of F1 hybrids derived from either intra- or inter-population crosses between Saccharina latissima strains from two localities, southern Brittany, France and the Faroe Islands, did not identify any clear advantage of inter- compared to intra-population crosses. Breeding based on locally-resourced strains would therefore appear to be a valid approach for current strain selection programs. The study also established a large collection of gametophyte strains from multiple sites for future breeding programs and showed that these strains retained the capacity to become fertile after more than ten years in culture.

genetics↗

bioRxiv2025

Genetic structure of sugar kelp in the St. Lawrence Estuary and Gulf (Quebec, Canada)

The sugar kelp, Saccharina latissima is cultivated at low scale in Quebec, Canada and current practice involve seeding meiospores or gametophyte stocks onto spools carrying twine and transferring these to a seaweed farm site. As the stocks can originate from locations spanning several hundreds of kilometers from the farm sites, such practice could involve genetic contamination and disrupt local adaptations. Assessing genetic structure can inform of the potential risks associated with this practice. Here we characterized the genetic diversity and structure of S. latissima from locations in the St. Lawrence Estuary and Gulf at both microsatellite loci (308 sporophytes at 22 loci in 16 sites) and genomic markers (228 sporophytes at 6578 single nucleotide polymorphisms in 13 sites). Several populations had low heterozygosity values and significant FIS values at microsatellite loci. No genetic structure was found among populations with microsatellite loci but strong genetic structuring was found with the genomic data. Population structure followed a geographic pattern and was congruent with major currents. Individuals from the wild population in the vicinity of the farm site were genetically distinct from the sporophytes on the growing lines that belong to a genetically distinct group. There was no significant genetic differentiation between wild individuals living in proximity of the farm site and another wild population of the same area. Hence aquaculture practices have not resulted in changes in the genetic composition of the wild population at large scale. Our results are important to guide future conservation efforts and for the seaweed farming industry.

evolutionary biology↗

bioRxiv2025

Wild and farmed Saccharina latissima in Europe: genetic insights for sustainable cultivation, traceability and environmental challenges

Kelp cultivation is expanding rapidly worldwide, although the aquaculture of Saccharina latissima (sugar kelp) in Europe remains in its early stages. However, major concerns have emerged about the potential impact of selected cultivars of the species on native populations of S. latissima which are already vulnerable to stressors including climate change. To address these concerns and support sustainable cultivation, it is essential to characterise genetic diversity and structure of wild kelp populations to monitor potential farm-to-wild gene flow. In this study we used 21 microsatellite loci to characterise the genetic structure of 24 natural and 3 farmed populations of S. latissima along European coasts. Results confirmed strong genetic differentiation between the northern and southern coasts, refining the boundaries between these two clusters compared to previous studies. Within each cluster, a clear genetic substructure was detected, with population differentiation being far more pronounced in the southern cluster. Cultivated sporophytes exhibited pedigrees that were all traced back to the local parent populations. Bayesian model-based structure analysis, discriminant analysis of principal components and assignment tests revealed no significant genetic differentiation between the farms and their wild populations. This indicates that farmed populations and neighbouring populations share the same gene pool, reflecting current cultivation practices. These findings contribute to understanding risks of gene flow between wild and farmed populations and demonstrate that strain traceability is feasible. Additionally, the study highlights the challenge European seaweed farmers face in securing reliable seedling stock, especially in the context of global change.

genetics↗

bioRxiv2024

Structural and evolutionary features of red algal UV sex chromosomes

BackgroundSex chromosomes in red algae have remained relatively understudied, despite their fundamental role in understanding the evolution of sex determination across eukaryotes. In this study, we investigate the structure, gene composition, and evolutionary history of the U and V sex chromosomes in four Gracilaria species, which diverged approximately 100 million years ago (MYA). ResultsOur findings reveal that UV sex chromosomes, previously identified in green and brown algae as well as bryophytes, have also evolved in red algae, contributing to the diversity of sex determination systems across eukaryotes. The shared orthology of conserved sex-determining region (SDR) genes between Gracilaria and distantly related red algae suggests that this system may have originated approximately 390 MYA, making it one of the oldest known sex chromosome systems. The SDR in Gracilaria is relatively small but contains conserved gametologs and V-specific genes involved in transcriptional regulation and signaling, suggesting their essential role in sexual differentiation. Unlike the conserved V-specific genes, U-specific genes appear absent, pointing to a dominant role of the V chromosome in sex determination. The evolution of Gracilaria sex chromosomes involved recombination suppression, gene relocations, duplications, and potential gene loss. Despite their ancient origin, the sex chromosomes show low levels of degeneration, likely due to haploid purifying selection during the gametophytic phase of the life cycle. ConclusionThis study provides the first detailed characterization of the U and V sex chromosomes in red algae, preparing the ground for future studies on reproductive life cycles and speciation in this understudied group of eukaryotes.

evolutionary biology↗

bioRxiv2023

Temporal genomics help in deciphering neutral and adaptive patterns in the contemporary evolution of kelp populations

The long-term persistence of species in the face of climate change can be evaluated by examining the interplay between selection and genetic drift in the contemporary evolution of populations. In this study, we focused on spatial and temporal genetic variation in four populations of the cold-water kelp Laminaria digitata using thousands of SNPs (ddRAD-seq). These populations were sampled from the center to the south margin in the North Atlantic at two different time points, spanning at least two generations. By conducting genome scans for local adaptation from a single time point, we successfully identified candidate loci that exhibited clinal variation, closely aligned with the latitudinal changes in temperature. This finding suggests that temperature may drive the adaptive response of kelp populations, although other factors, such as the species demographic history should be considered. Furthermore, we provided compelling evidence of positive selection through the examination of allele frequency changes over time, offering additional insights into the impact of genetic drift. Specifically, we detected candidate loci exhibiting temporal differentiation that surpassed the levels typically attributed to genetic drift at the south margin, confirmed through simulations. This finding was in sharp contrast with the lack of detection of outlier loci based on temporal differentiation in a population from the North Sea, exhibiting low levels of genetic diversity, that further decreased over time. These contrasting evolutionary scenarios among populations can be primarily attributed to the differential prevalence of selection relative to genetic drift. In conclusion, our study highlights the potential of temporal genomics to gain deeper insights into the contemporary evolution of marine foundation species in response to rapid environmental changes.

evolutionary biology↗

bioRxiv2023

Influence of oceanography and geographic distance on genetic structure: how varying the sampled domain influences conclusions in Laminaria digitata

Understanding the environmental processes shaping connectivity can greatly improve management and conservation actions which are essential in the trailing edge of species distributions. In this study, we used a dataset built from 32 populations situated in the southern limit of the kelp species Laminaria digitata. By extracting data from 11 microsatellite markers, our aim was to (1) refine the analyses of population structure, (2) compare connectivity patterns and genetic diversity between island and mainland populations and (3) evaluate the influence of sampling year, hydrodynamic processes, habitat discontinuity, spatial distance and sea surface temperature on the genetic structure using a distance-based redundancy analysis (db-RDA). Analyses of population structure enabled to identify well connected populations associated to high genetic diversity, and others which appeared genetically isolated from neighboring populations and showing signs of genetic erosion verifying contrasting ecological (and demographic) status in Brittany and the English Channel. By performing db-RDA analyses on various sampling sizes, geographic distance appeared as the dominant factor influencing connectivity between populations separated by great distances, while hydrodynamic processes were the main factor at smaller scale. Finally, Lagrangian simulations enabled to study the directionality of gene flow which has implications on source-sink dynamics. Overall, our results have important significance in regard to the management of kelp populations facing pressures both from global warming and their exploitation for commercial use.

evolutionary biology↗

bioRxiv2023

THE RHODOEXPLORER PLATFORM FOR RED ALGAL GENOMICS AND WHOLE GENOME ASSEMBLIES FOR SEVERAL GRACILARIA SPECIES

Macroalgal (seaweed) genomic resources are generally lacking as compared to other eukaryotic taxa, and this is particularly true in the red algae (Rhodophyta). Understanding red algal genomes is critical to understanding eukaryotic evolution given that red algal genes are spread across eukaryotic lineages from secondary endosymbiosis and red algae diverged early in the Archaeplastids. The Gracilariales are highly diverse and widely distributed order whose species can serve as ecosystem engineers in intertidal habitats, including several notorious introduced species. The genus Gracilaria is cultivated worldwide, in part for its production of agar and other bioactive compounds with downstream pharmaceutical and industrial applications. This genus is also emerging as a model for algal evolutionary ecology. Here, we report new whole genome assemblies for two species (G. chilensis and G. gracilis), a draft genome assembly of G. caudata, and genome annotation of the previously published G. vermiculophylla genome. To facilitate accessibility and comparative analysis, we integrated these data in a newly created web-based portal dedicated to red algal genomics (https://rhodoexplorer.sb-roscoff.fr). These genomes will provide a resource for understanding algal biology and, more broadly, eukaryotic evolution.

genomics↗