Biology subjects

Raffard, A.

Publications and source records attributed to Raffard, A..

10 recordsLinked to original sources

bioRxiv2026

A few genes modulate the ecological impact of a freshwater fish species on food webs and ecosystem functions

Genetic diversity within species can shape food webs and ecosystem functioning as strongly as species diversity, yet the genomic architecture underlying these effects remains unclear. Gene-to-ecosystem relationships may arise from genome-wide diversity, from a limited number of ecologically-important genes, or a combination of both. Experimental tests of these hypotheses are lacking. Here, we manipulated genomic diversity of a top-predatory fish in mesocosms under ambient or warm conditions, and quantified ecological responses spanning fish biomass, prey communities and ecosystem functions. Genome-wide diversity explained few ecological responses, with moderate effects (r=0.260). In contrast, variation at specific candidate SNPs predicted all ecological responses consistently across climatic conditions, with effect sizes being more than twice those of genome-wide estimates (r=0.599). Moreover, combining information from small subsets of candidate SNPs outperformed both single-locus and genome-wide diversity for all ecological responses (r=0.841), consistent with an oligogenic architecture for gene-to-ecosystem relationships. Enrichment analyses revealed functional pathways related to growth, development and metabolic regulation, driven by a small set of pleiotropic genes. We demonstrate that the ecological consequences of intraspecific genetic variation arose from a limited fraction of the genome, highlighting the importance of functional genomic structure, rather than genome-wide diversity alone, in shaping eco-evolutionary dynamics.

ecology↗

bioRxiv2026

Warming and predation drive rapid evolution of ecosystem functioning but not functional traits

Global environmental change can rapidly reshape phenotypic trait distributions through adaptive and neutral processes. Yet, disentangling their relative contributions remains a major challenge, particularly for traits underpinning ecosystem functioning. Using a two-year mesocosm study, we experimentally evolved Asellus aquaticus under contrasting temperature and predation regimes to test how the joint influence of these global change pressures shape the evolution of traits and ecosystem functioning. We show that classic functional traits (body size and metabolic rate) showed no evidence of divergent evolution across evolutionary conditions, while ecosystem function itself, namely decomposition rate, has evolved rapidly and differently depending on evolutionary conditions, with the highest decomposition rate observed for Asellus populations exposed to high temperatures in the absence of their predator. A Pst/Fst comparison revealed that divergence in metabolic rate among evolutionary conditions was mainly driven by genetic drift, whereas, for body mass and decomposition rate, non-neutral processes (natural selection and/or plasticity) were also involved, albeit in a different way. By demonstrating that predation and temperature can influence the evolution of an ecosystem function over a few generations, this study represents an important first step toward uncovering the combined effects of global change on the eco-evolutionary dynamics of ecosystems.

evolutionary biology↗

bioRxiv2026

Early life thermal plasticity and adaptive divergence among populations of Arctic charr (Salvelinus alpinus)

Climate warming alters the thermal environment experienced by ectotherms, whose physiological performance and fitness are constrained by temperature. Early life stages are often the temperature-sensitive phases of the life cycle, particularly in freshwater stenotherms such as the Arctic charr (Salvelinus alpinus). In this study, we used a common garden approach to compare the response and phenotypic plasticity of four charr populations to warmer conditions. These populations inhabit thermally contrasted lakes, including both native and introduced populations. We reared embryos at either an optimal (5{degrees}C) or a warmer (8.5{degrees}C) temperature. We tested adaptive divergence among populations in four traits (survival, incubation duration, body length and yolk sac volume) using Qst - Fst comparisons. We found that warmer temperature reduced body size, survival and incubation time, while thermal reaction norms differed among populations. Unexpectedly, populations originating from warmer environments did not consistently exhibit higher trait values under elevated temperatures. In contrast, the colder high-altitude population exhibited higher survival rates and lower yolk reserves for a given size under heat stress than the other populations. Our results highlight substantial variation among populations in responses to heat stress, emphasizing the complexity of predicting population responses to climate warming.

evolutionary biology↗

bioRxiv2025

A century of allopatry: plasticity and rapid selection shape phenotypic trait variability under contrasting environments.

Allopatric isolation under contrasting environments can drive rapid phenotypic divergence, even over contemporary timescales. Rapid changes in morphology or physiology can allow organisms to adapt to biotic and abiotic characteristics of their habitats. While studying metabolism, growth and resources needs may allow to understand adaptation to several selective pressures, these traits are rarely jointly considered. We investigated morphological, growth, and metabolic divergence in two allopatric populations of Arctic charr (Salvelinus alpinus) sharing a common evolutionary origin but inhabiting contrasting environments. We combined field observations, common garden and quantitative genetic approaches to disentangle contributions of genetic divergence and plasticity to phenotypic variability. Wild adults differed in body shape and growth trajectories, potentially reflecting plasticity related to resource availability and temperature variations. Under common garden conditions, juveniles displayed inter-population differences in routine metabolic rate, its allometric scaling with body mass. These patterns suggest divergent selection on physiological traits. Despite low neutral genetic differentiation, phenotypic divergence unfolded in fewer than 100 years, suggesting that plasticity and selection can promote rapid multi-trait changes. These findings highlight that considering changes in physiological, growth and morphological traits can reveal the adaptive potential of small, isolated populations facing rapid environmental change.

evolutionary biology↗

bioRxiv2025

Behavior Outpaces Form when Linking Traits to Ecological Responses within Populations: A Meta-Analysis

Intraspecific variability is fundamental to ecology, yet we still know remarkably little about what governs the strength of the associations between traits expressed by individuals and ecological dynamics. To explore this overlooked aspect of diversity, we asked whether the strength of correlations between traits and a wide spectrum of ecological responses could differ (i) between intraspecific levels (among vs. within populations), (ii) among ecological responses across levels of biological organization (from ecological performance to ecosystem functioning), and (iii) among trait types (morphology, physiology, and behavior). We performed a meta-analysis synthesizing over a thousand effect sizes from nearly two hundred studies spanning approximately a hundred animal species across a broad range of traits and ecological responses. The average effect size was |r| = 0.26 (95% confidence interval: 0.21 - 0.30). At the individual level, effect sizes were larger for ecological performance (foraging, diet) than for fitness (reproduction), and tended to be larger for community responses (e.g., community composition of surrounding organisms). Physiology and behavior showed larger effect sizes than morphology. Our meta-analysis not only confirms that intraspecific trait variability is central to ecological dynamics, but also highlights physiology and behavior as key traits for unraveling the ecological consequences of individual variability.

ecology↗

bioRxiv2021

Dispersal syndromes affect ecosystem functioning in ciliate microcosms

Dispersal is a key process mediating ecological and evolutionary dynamics. Its effects on metapopulations dynamics, population genetics or species range distribution can depend on phenotypic differences between dispersing and non-dispersing individuals (i.e., dispersal syndromes). However, scaling up to the importance of dispersal syndromes for meta-ecosystems have rarely been considered, despite intraspecific phenotypic variability is now recognised as an important factor mediating ecosystem functioning. In this study, we characterised the intraspecific variability of dispersal syndromes in twenty isolated genotypes of the ciliate Tetrahymena thermophila to test their consequences for biomass productivity in communities composed of five Tetrahymena species. To do so, dispersers and residents of each genotype were introduced, each separately, in ciliate communities composed of four other competing species of the genus Tetrahymena to investigate the effects of dispersal syndromes. We found that introducing dispersers led to a lower biomass compared to introducing residents. This effect was highly consistent across the twenty T. thermophila genotypes despite their marked differences of dispersal syndromes. Finally, we found a strong genotypic effect on biomass production, confirming that intraspecific variability in general affected ecosystem functions in our system. Our study shows that intraspecific variability and the existence of dispersal syndromes can impact the functioning of spatially structured ecosystems in a consistent and therefore predictable way.

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↗

bioRxiv2019

Loss of genetic diversity in wild fish populations reduces biomass stability over time.

Genetic diversity sustains species adaptation. However, it may also support key ecosystems functions and services that can be altered by the worldwide loss of genetic diversity. Here, using long-term wild fish data, we demonstrate that populations with high genetic diversity do not reach higher biomasses than populations with low genetic diversity. Nonetheless, populations with high genetic diversity have much more stable biomasses over recent decades than populations having suffered from genetic erosion, which has implications for the provision of ecosystem services and the risk of population extinction. Our results strengthen the importance of adopting prominent environmental policies to conserve this important biodiversity facet.

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↗