Biology subjects

Guyot, L.

Publications and source records attributed to Guyot, L..

4 recordsLinked to original sources

bioRxiv2026

Environmental tolerance, species interaction, and the link between the fundamental and realized niches: Insights from a hypersaline planktonic system

The impacts of a changing abiotic environment on fitness and performance arise not only from low tolerance to new environmental conditions, but also from changes in the abundance and interaction intensity with other species. The strength of the interaction may itself depend on how well each species performs across environments, but there is a dearth of studies investigating how intrinsic fitness and interaction intensity covary across an abiotic environmental gradient. We addressed this question in a hypersaline consumer-resource system: the microalga Dunaliella spp. grazed by the brine shrimp Artemia franciscana. We exposed four Dunaliella strains to a range of salinities above seawater, with or without brine shrimps, and tracked their population sizes over time and the survival of their predators, to estimate basic parameters of a Lotka-Volterra model. We found that the intrinsic growth rate of algae, the survival rate of predators, and the per-capita predation rate, all varied with salinity and algal strain. Significant interactions between strain and salinity further revealed that these ecological responses to salinity are evolvable. Together with correlations between demographic parameters across salinity, this suggests that predation may influence the evolution of salinity tolerance curves, blurring the line between the fundamental and realized niches.

ecology↗

bioRxiv2025

Co-adapting but not static predators facilitate prey adaptation to a fluctuating environment

Understanding how between-species interactions influence adaptation and population persistence in the face of environmental change is one of the greatest challenges for modern ecology and evolution, with important implications for conservation, and other applied fields. As predation is ubiquitous and may have strong demographic and selective impacts, it is likely to alter how prey respond to a changing environment. However, whether and how adaptation in prey depends on the way selection operates on predators remains little understood. We investigate this question by modeling the evolution of a preys trait whose optimum phenotype for fitness changes with the abiotic environment, and which also influences predation via its match with a trait of a predator species. We first show that when coevolutionary processes explicitly emerge from interactions among individuals, maladaptation in prey is not proportional to the difference between their optimum phenotype and that of predators, as assumed in most coevolutionary models. In a fluctuating environment, how well the prey track their moving optimum crucially depends on whether and how the predator evolves. Adaptive tracking of the optimum in prey is facilitated if predators track the same optimum, but hampered if predators have a fixed optimum, or cannot evolve. With eco-evolutionary dynamics, phenotypic mismatch reduces the population size of predators, thus decreasing the strength of predatory selection, but the qualitative influence of predation on prey maladaptation remains otherwise similar. Our findings highlight the importance of the evolutionary context of predators for their impacts on prey, and challenge conservation strategies for prey based on removing their predators. Significance statementSpecies in the wild face the dual challenge of adapting to their changing physical environment and coping with detrimental interactions with other species, including predators. While evolution by natural selection may jointly overcome both these challenges, the outcome of this process depends on whether the selective forces from predation and environmental change reinforce or oppose each other. Here, we show that the influence of coevolving predators on prey adaptation to a changing environment strongly depends on the selective scenario for the predators. Adaptation in prey is facilitated if predators also adapt to the changing environment, but hampered if selection favors a constant phenotype in predators. Our results challenge the relevance of predator removal as a conservation strategy to preserve prey.

evolutionary biology↗

bioRxiv2025

Loci under balancing selection facilitate the emergence of pseudo-overdominance and recombination suppression

Loci under strong balancing selection, such as sex-determining, mating-type, and self-incompatibility loci, are frequently flanked by regions of suppressed recombination. The reasons why recombination suppression evolves around these loci remain poorly understood. Here, we propose that one reason may be that loci under balancing selection facilitate the emergence of pseudo-overdominance, a phenomenon under which linked partially recessive deleterious mutations in repulsion mimic overdominance. Pseudo-overdominance arises when linkage disequilibrium gradually builds up between recessive deleterious mutations, often due to strong genetic linkage and genetic drift. Once complementary haplotypes form, homozygous and recombinant offspring are selected against because they carry homozygous recessive deleterious mutations. Using individual-based simulations, we demonstrate here that the presence of loci under balancing selection eases the establishment of pseudo-overdominance, by facilitating the maintenance of partially recessive deleterious mutations and linkage disequilibrium in their flanking regions. This occurs particularly in regions with low recombination rates and a high load of partially recessive deleterious mutations, which can be found in specific genomic regions in natural populations. We further show that such resulting pseudo-overdominance can render more likely the evolution of recombination suppression around permanently heterozygous loci, preventing the creation of unfit homozygous recombinant offspring. These results suggest new avenues for understanding the evolution of loci under balancing selection, sex chromosomes and supergenes, and shed new light on the mechanisms driving genome evolution.

evolutionary biology↗

bioRxiv2024

Sheltered load in fungal mating-type chromosomes revealed by fitness experiments

Sex chromosomes and mating-type chromosomes can carry large regions with suppressed recombination. As a result of a lower efficacy of selection, recessive deleterious mutations are expected to accumulate in these non-recombining regions. Multiple genomic analyses have indirectly inferred the presence of deleterious mutations in sex and mating-type chromosomes, but direct experimental evidence remains scarce. Here, we performed fitness assays in fungi with megabase-large and young non-recombining regions around the mating-type locus, using three Sordariales species, to test whether heterokaryons (diploid-like, heterozygous at the mating-type locus) exhibited a fitness advantage over homokaryons (haploid-like, with a single mating-type allele), in terms of spore germination dynamics or mycelium growth speed, under different conditions of light and temperature. We found a faster growth of heterokaryons compared to one of the homokaryons for Podospora anserina at 18{degrees}C and for Schizothecium tetrasporum and Schizothecium tritetrasporum at 22{degrees}C under light. These findings suggest the presence of a sheltered load, i.e., recessive deleterious mutations at the heterozygous state in or near non-recombining regions, associated to a specific mating-type allele. Genomic analyses indeed suggested that the non-recombining regions around the mating-type locus likely carries heterozygous deleterious mutations, while the rest of the genome was mostly homozygous. We also showed that the difference in growth rates did not result from different numbers or densities of nuclei between homokaryons and heterokaryons. Leveraging the experimental assets of fungi, allowing cultivating separately haploid-like and diploid-like life stages, our experiments provided one of the rare direct experimental evidence of sheltered load around mating-compatibility loci, which is crucial for our understanding of sex-related chromosome evolution. Social Media AbstractExperimental evidence for sheltered load around the mating-type locus in filamentous fungi: slower growth of haploid versus diploid-like mycelia, revealing recessive deleterious mutations, in Podospora anserina and other Sordariales fungi.

evolutionary biology↗