Biology subjects

Santoul, F.

Publications and source records attributed to Santoul, F..

4 recordsLinked to original sources

bioRxiv2024

Genetic-based inference of densities, effective and census sizes of expanding riverine meta-populations of an invasive large-bodied freshwater fish (Silurus glanis L.).

Effective (Ne) and census (Nc) population sizes are key eco-evolutionary parameters. Jointly estimating them have an important practical value for efficient conservation and wildlife monitoring and management. Assessing Ne and Nc remains however challenging for elusive, rare species or species inhabiting in complex habitats like large rivers. Genetic-based Ne estimations could help resolve complex situations, as only a handful of genotyped individuals are needed to estimate Ne, and then NC can be subsequently using an Ne/NC ratio. However, most Ne estimation methods are based on restrictive assumptions (e.g. Wright-Fisher model) making them inappropriate for inferring Ne and Nc for populations and species exhibiting complex dynamics. Here, we aimed at estimating Ne, NC and densities for meta-populations of a large invasive freshwater fish (the European catfish Silurus glanis) that has been introduced in the Garonne-Dordogne river basin (Southwestern France), using a framework that combines multiple data sources and approaches. First, we characterized spatial patterns of genetic variation using microsatellite genotype data, revealing a significant isolation by distance pattern informing about the species dispersal capacities. We then detected four genetically-distinct clusters of individuals coexisting in the river basin that might be the result of multiple introductions from different genetic sources. Further, we characterized the demographic expansion of the species at the river basin scale by analyzing data from a multidecadal demographic monitoring survey, and estimated a specific Ne/Nc ratio for this species. We finally combined all the gathered information to design four competing demo-genetic models accounting for all the complexity of S. glanis meta-populations inhabiting the river basin. We simulated data under these models and then inferred Ne, Nc and densities through approximate Bayesian computation and random forest procedures. We show how multiple genetic and non-genetic approaches can be combined to estimate Ne and Nc in hard-to-monitor meta-populations exhibiting complex demo-evolutionary dynamics.

ecology↗

bioRxiv2020

Intraspecific diversity loss in a predator species alters prey community structure and ecosystem functions

AO_SCPLOWBSTRACTC_SCPLOWLoss in intraspecific diversity can alter ecosystem functions, but the underlying mechanisms are still elusive, and intraspecific biodiversity-ecosystem function relationships (iBEF) have been restrained to primary producers. Here, we manipulated genetic and functional richness of a fish consumer (Phoxinus phoxinus), to test whether iBEF relationships exist in consumer species, and whether they are more likely sustained by genetic or functional richness. We found that both genotypic and functional richness affected ecosystem functioning, either independently or in interaction. Loss in genotypic richness reduced benthic invertebrate diversity consistently across functional richness treatments, whereas it reduced zooplankton diversity only when functional richness was high. Finally, both losses in genotypic and functional richness altered essential functions (e.g. decomposition) through trophic cascades. We concluded that iBEF relationships lead to substantial top-down effects on entire food chains. The loss of genotypic richness impacted ecological properties as much as the loss of functional richness, probably because it sustains "cryptic" functional diversity.

ecology↗

bioRxiv2018

Intraspecific variation and warming have comparable effects on eco-evolutionary dynamics.

Phenotypic or genotypic variation within species affects ecological processes, from populations to ecosystems. However, whether the ecological imprint of intraspecific variation is substantial compared to key environmental drivers, and persistent enough to carry over to next generations is still questioned. Here, we experimentally showed that intraspecific variation manipulated in a freshwater fish (the European minnow, Phoxinus phoxinus) led to ecological and transgenerational carry-over effects that were as strong as those of varying temperature by 2{degrees}C. Specifically, variation in fish body mass, growth rate and activity altered the size and abundance of prey, which ultimately affected traits and survival of the next fish generation. Temperature variation modulated other ecosystem functions (e.g. litter decomposition) that were also associated to transgenerational carry-over effects. Our results demonstrate that shifting genotypes or phenotypes in wild populations can have substantial and persistent consequences on ecosystems with a similar intensity than climatic variation.

ecology↗

bioRxiv2018

The community and ecosystem consequences of intraspecific diversity: a meta-analysis

Understanding the relationships between biodiversity and ecosystem functioning has major implications. Biodiversity-ecosystem functioning relationships are generally investigated at the interspecific level, although intraspecific diversity (i.e. within-species diversity) is increasingly perceived as an important ecological facet of biodiversity. Here, we provide a quantitative and integrative synthesis testing, across diverse plant and animal species, whether intraspecific diversity is a major driver of community dynamics and ecosystem functioning. We specifically tested (i) whether the number of genotypes/phenotypes (i.e. intraspecific richness) or the specific identity of genotypes/phenotypes (i.e. intraspecific variation) in populations modulate the structure of communities and the functioning of ecosystems, (ii) whether the ecological effects of intraspecific richness and variation are strong in magnitude, and (iii) whether these effects vary among taxonomic groups and ecological responses. We found a non-linear relationship between intraspecific richness and community and ecosystem dynamics that follows a saturating curve shape, as observed for biodiversity-function relationships measured at the interspecific level. Importantly, intraspecific richness modulated ecological dynamics with a magnitude that was equal to that previously reported for interspecific richness. Our results further confirm, based on a database containing more than 50 species, that intraspecific variation also has substantial effects on ecological dynamics. We demonstrated that the effects of intraspecific variation are twice as high as expected by chance, and that they might have been underestimated previously. Finally, we found that the ecological effects of intraspecific variation are not homogeneous and are actually stronger when intraspecific variation is manipulated in primary producers than in consumer species, and when they are measured at the ecosystem rather than at the community level. Overall, we demonstrated that the two facets of intraspecific diversity (richness and variation) can both strongly affect community and ecosystem dynamics, which reveals the pivotal role of within-species biodiversity for understanding ecological dynamics.

ecology↗