Biology subjects

Le Cam, S.

Publications and source records attributed to Le Cam, S..

3 recordsLinked to original sources

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↗

bioRxiv2024

Longevity and environmental temperature modulate mitochondrial DNA evolution in fishes

The link between longevity and mitochondrial function has been documented for years. Since mitochondrial DNA (mtDNA) encodes for electron transport system (ETS) proteins, we could suspect that its evolution is linked with that of longevity. A negative relationship has been documented between the synonymous substitution rate and lifespan when analyzing the whole mitochondrial genome in animals. In this study, we aimed to confirm this negative correlation for each of the mitochondrial protein coding genes (mtPCGs) and explore potential relationships between adaptation to extreme temperatures and the evolution of mtDNA. To this end, we selected 112 species of fish with a wide range of longevity as well as divergences in environmental temperature, which is a good proxy for energy metabolism in these animals. Our results 1) challenge the "rate of living" theory by not showing any correlation between longevity and environmental temperature, 2) confirm the negative relationship between substitution rate and longevity for each of the 13 mtPCGs, and 3) highlight for the first time a link between high conservation of the three COX genes and adaptation to warmer temperatures in fish. By challenging a paradigm and extending the conclusions made for mtDNA to individual genes, our study opens a wide field to be explored concerning study of the aging process. Moreover, the specific link between the evolution of COX genes and temperature tolerance confirms the importance of complex IV in adaptation to extreme temperatures and, more generally, the importance of distinguishing gene families when studying mtDNA evolution in animals.

evolutionary biology↗

bioRxiv2022

Discordant population structure inferred from male- and female-type mtDNAs from Limecola balthica, a bivalve species characterized by doubly uniparental inheritance of mitochondria

Doubly Uniparental Inheritance (DUI) of mitochondria is a remarkable exception to the Strictly Maternal Inheritance (SMI) in metazoans. In species characterized by DUI --almost exclusively gonochoric bivalve mollusks--females (F) transmit mitochondria to offspring of both sexes, while males (M) pass on their mitochondria exclusively to their sons. Under DUI, males are heteroplasmic, somatic tissues containing F-transmitted mtDNA and gametic cells containing M-transmitted mtDNAs. The aforementioned transmission routes make M- and F-transmitted mtDNA interesting as sex-specific markers which can differ in their effective population sizes, mutation rates, and selective constraints. For these reasons, looking at both markers can provide significant insights into the genetic structure of populations and investigate its determinants. In this study, we document differences in genetic diversity, divergence, inter-populational differentiation and biogeographic structure between M- and F-type cox1 mt genes in the Baltic tellin (Macoma balthica) to test whether cox1m and cox1f genes bear the marks of similar phylogeographic histories. These markers were sequenced for 302 male individuals sampled from the North Sea to the Gironde Estuary (Southern France) encompassing the intra-subspecific M. b. rubra hybrid zone in the Gulf of Saint Malo. Both genes supported a scenario of cladogenesis of M.b. rubra clades prior to the last glacial maximum. Nucleotide diversity and net divergence were over twice higher in cox1m compared to cox1f. Genetic differentiation between northern and southern populations was nearly 3 times higher at cox1m compared to cox1f (global {Phi}ST = 0.345 and 0.126 respectively) and the geographic localization of the strongest genetic break significantly differed between the markers (Finistere Peninsula at cox1f; Cotentin Peninsula at cox1m, [~]250 km apart). A higher mutation rate, relaxed negative selection and differences in effective population sizes (depending on locations) at cox1m could explain differences in population genetic structure. As both F- and M-type mtDNAs interact with nuclear genes for oxidative phosphorylation and ATP production, geographical discordances in genetic clines in a context of secondary contact could be linked to mito-nuclear genetic incompatibilities.

evolutionary biology↗