Biology subjects

Lefevre, F.

Publications and source records attributed to Lefevre, F..

5 recordsLinked to original sources

bioRxiv2026

Multiscale intraspecific variation and coordination of hydraulic traits in silver fir

O_LIIntraspecific variability in hydraulic and morphological traits may alter projections of forest vulnerability to climate change. Recognizing multiscale nature is essential, as trait relationships within populations may not reflect those across the species range. C_LIO_LIWe assessed variability in 11 traits in 10 natural populations of Abies alba across environmental and phylogeographic gradients to evaluate potential impacts on drought vulnerability. We quantified trait variation within and among populations, tested effects of climate, phylogeny and local factors, and evaluated trait coordination across scales. C_LIO_LIHydraulic safety traits and wood density showed low variability, indicating strong constraints. In contrast, water-use and efficiency traits were highly variable. Aridity influenced several traits, but reduced variance was detected only for leaf residual conductance and succulence consisted with stabilising selection. Trait coordination was weak within populations than among populations. C_LIO_LIOverall, A. alba combines constrained hydraulic safety traits with variable water use traits. This may buffer drought impacts but limits shifts in hydraulic safety margins, potentially increasing risks of hydraulic failure, especially in humid environments where populations lack the capacity to tolerate prolonged dry periods. Thus, our findings highlight the need to account for scale-dependent trait variability, coordination, and their underlying drivers when predicting species adaptive capacity to drought. C_LI

plant biology↗

bioRxiv2025

Beyond Proxies: Towards ecophysiological indicators of drought resistance for forest management

As drought-induced mortality increases globally in forest biomes, it becomes necessary for foresters to have access to reliable predictors of species vulnerability to drought and mortality risk under different climatic scenarios. On the one hand, there exist several "operational" indicators of drought resistance, which are based on observations, expert knowledge and species bioclimate (e.g. Ellenberg, Rameau, ClimEssences). On the other hand, as traits can now be measured at high throughput, functional traits (such as plant hydraulic traits) have been increasingly used to assess species vulnerability to hydraulic failure, a key process of tree mortality under drought. However, this mechanistic approach has never been compared to the operational approach. In this study, we review if indicators commonly used by foresters provide information on Abies species vulnerability to hydraulic failure. We measured a set of traits in a common garden experiment of closely related Mediterranean Abies species. These traits were used as inputs to the SurEau model to compute a single indicator of vulnerability (Time to Hydraulic Failure - THF) and to assess mortality risk in future climate. We found that among circum-Mediterranean firs, a high THF was mainly due to high water losses after stomatal closure. Some operational indicators are good proxies of THF, however they are not available for all species, reduce a species to a single value and have the same limitations as species distribution models. We argue that the ecophysiological approach could help foresters in species selection and in estimating the risk faced by forest tree species in a changing climate. While accounting for the variability of traits, hydraulic models can be forced with different climatic scenarios allowing hydraulic failure risk assessment by the end of the century. HighlightsO_LIIntegrating ecophysiological traits in a process-based model allows the computation of an accurate indicator of vulnerability: the Time to Hydraulic Failure (THF). C_LIO_LIFor Abies species, "operational" indicators, i.e. indicators used by foresters and land managers, are mutually consistent and can be simplified proxies of the vulnerability to hydraulic failure. C_LIO_LIMore research on intra-specific variability is needed to assess the evolutionary potential of Euro-Mediterranean Abies species. C_LI

ecology↗

bioRxiv2023

From the third to the seventh generation of selection for muscle fat content in rainbow trout: Consequences for flesh quality

Muscle lipid content was shown to affect many quality features in salmonids in both raw and processed fillets. The objective of the present work was to assess the consequences of 7 generations of divergent selection for muscle adiposity on some rainbow trout flesh quality and muscle parameters. Fish from Lean (L) and Fat (F) lines had a similar body weight but L fish were longer and had consequently lower condition factor values. Carcass yield was not affected by selective breeding, but L fish had lower hepato- and gonado-somatic indexes, a bigger head, and lower fillet yield than F fish. A difference of more than 15 points in mean fat-meter(R) values (genetic selection criteria) was measured between the two lines. Mean muscle lipid content was 5.0{+/-}1.0% for L line vs 13.5{+/-}2.2% for F line. An absolute difference of more than 6% was measured in fillet dry matter content between the two lines, for raw, cooked, and smoked fillets. Raw fillets from F fish were lighter (L*>) and more colorful (a* and b*>), but softer than those from the L line. Quality parameters of cooked fillets were very similar between the two lines, whereas smoked fillets exhibited, between the two lines, similar differences than raw fillets. A large difference in white muscle fiber size was observed, fish from F line having higher fiber mean diameter, a lower proportion of small fibers, and a higher proportion of large fibers. Sex effects were observed on these immature fish, on classically sex-related traits (GSI and head development), but also on muscle fiber size. Moreover, these effects were more marked in F line. Correlation analysis showed that raw fillet color was positively related to muscle adiposity whereas mechanical resistance was negatively related. Raw fillet mechanical resistance was also negatively correlated to white muscle fiber size. Moreover, smoked fillet quality parameters were correlated to raw fillet ones. The relationships between muscle adiposity, but also muscle cellularity, and fillet quality were discussed. HighlightsO_LI7 generations of adiposity divergent selection affect raw and smoked fillet quality. C_LIO_LISelective breeding led to a noteworthy response in white muscle cellularity. C_LIO_LISome differences between male and female was measured in immature pan-size trout. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=195 SRC="FIGDIR/small/569019v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@10b25f6org.highwire.dtl.DTLVardef@e9402aorg.highwire.dtl.DTLVardef@173b1f9org.highwire.dtl.DTLVardef@a9898b_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2021

A hierarchical Bayesian model to investigate trade-offs between growth and reproduction in a long-lived plant

1A trade-off between growth and fecundity, reflecting the inability of simultaneously investing in both functions when resources are limited, is a fundamental feature of life history theory. This particular trade-off is the result of evolutionary and environmental constrains shaping reproductive and growth traits, but it remains difficult to pinpoint in natural populations of long-lived plants. We developed a hierarchical Bayesian model to estimate the inter-individual correlation among growth and reproduction, using observations at individual level over several years combined with resource simulations from an ecophysiological-based model (CASTANEA). In the Bayesian model, the resource, simulated by CASTANEA and incorporated as a latent variable, is allocated to tree growth, reproductive buds initiation and fruit maturation. Then, we used individual random effects correlated among energetic sinks to investigate potential trade-offs. We applied this original approach to a Mediterranean coniferous tree, Atlas Cedar (Cedrus atlantica), at two contrasted levels of competition, high versus low density population. We found that trees initializing many reproductive buds had a higher growth. Moreover, a negative correlation was detected between growth and fruit survival during maturation. Finally, trees investing more resource to maturate fruits initiated less reproductive buds. The level of competition did not impact the sign of these three correlations, but changed the level of resource allocation: low density population favored growth whereas high density favored reproduction. The level of resource have an impact on individual strategies. This new modeling framework allowed us to detect various individual strategies of resource allocation to growth versus late-stage reproduction on the one hand, and to early-versus late-stage reproduction on the other hand. Moreover, the sign of the correlation between growth and reproductive traits depends on the stage of reproduction considered. Hence, we suggest that the investigation of potential trade-offs between growth and reproduction requires to integrate the dynamics of resource and sinks phenology, from initiation to maturation of reproductive organs.

ecology↗

bioRxiv2019

Combining statistical and mechanistic models to unravel the drivers of mortality within a rear-edge beech population

AO_SCPLOWBSTRACTC_SCPLOWSince several studies have been reporting an increase in the decline of forests, a major issue in ecology is to better understand and predict tree mortality. The interactions between the different factors and the physiological processes giving rise tree mortality, as well as the inter-individual variability in mortality risk, still need to be better assessed. This study investigates mortality in a rear-edge population of European beech (Fagus sylvatica L.) using a combination of statistical and process-based modelling approaches. Based on a survey of 4323 adult beeches since 2002 within a natural reserve, we first used statistical models to quantify the effects of competition, tree growth, size, defoliation and fungi presence on mortality. Secondly, we used an ecophysiological process-based model (PBM) to separate out the different mechanisms giving rise to temporal and inter-individual variations in mortality by simulating depletion of carbon stocks, loss of hydraulic conductance and damage due to late frosts in response to climate. The combination of all these simulated processes was associated with the temporal variations in the population mortality rate. The individual probability of mortality decreased with increasing mean growth, and increased with increasing crown defoliation, earliness of budburst, fungi presence and increasing competition, in the statistical model. Moreover, the interaction between tree size and defoliation was significant, indicating a stronger increase in mortality associated to defoliation in smaller than larger trees. Finally, the PBM predicted a higher conductance loss together with a higher level of carbon reserves for trees with earlier budburst, while the ability to defoliate the crown was found to limit the impact of hydraulic stress at the expense of the accumulation of carbon reserves. We discuss the convergences and divergences obtained between statistical and process-based approaches and we highlight the importance of combining them to characterize the different processes underlying mortality, and the factors modulating individual vulnerability to mortality.

ecology↗