Between but not within species variation in the distribution of fitness effects

New mutations provide the raw material for evolution and adaptation. The distribution of fitness effects (DFE) describes the spectrum of effects of new mutations that can occur along a genome, and is therefore of vital interest in evolutionary biology. Recent work has uncovered striking similarities in the DFE between closely related species, prompting us to ask whether there is variation in the DFE among populations of the same species, or among species with different degrees of divergence, i.e., whether there is variation in the DFE at different levels of evolution. Using exome capture data from six tree species sampled across Europe we characterised the DFE for multiple species, and for each species, multiple populations, and investigated the factors potentially influencing the DFE, such as demography, population divergence and genetic background. We find statistical support for there being variation in the DFE at the species level, even among relatively closely related species. However, we find very little difference at the population level, suggesting that differences in the DFE are primarily driven by deep features of species biology, and that evolutionarily recent events, such as demographic changes and local adaptation, have little impact

The GenTree Platform: growth traits and tree-level environmental data in 12 European forest tree species

Background: Progress in the field of evolutionary forest ecology has been hampered by the huge challenge of phenotyping trees across their ranges in their natural environments, and the limitation in high-resolution environmental information. Findings: The GenTree Platform contains phenotypic and environmental data from 4,959 trees from 12 ecologically and economically important European forest tree species: Abies alba Mill. (silver fir), Betula pendula Roth. (silver birch), Fagus sylvatica L. (European beech), Picea abies (L.) H. Karst (Norway spruce), Pinus cembra L. (Swiss stone pine), Pinus halepensis Mill. (Aleppo pine), Pinus nigra Arnold (European black pine), Pinus pinaster Aiton (maritime pine), Pinus sylvestris L. (Scots pine), Populus nigra L. (European black poplar), Taxus baccata L. (English yew), and Quercus petraea (Matt.) Liebl. (sessile oak). Phenotypic (height, diameter at breast height, crown size, bark thickness, biomass, straightness, forking, branch angle, fructification), regeneration, environmental in situ measurements (soil depth, vegetation cover, competition indices), and environmental modeling data extracted by using bilinear interpolation accounting for surrounding conditions of each tree (precipitation, temperature, insolation, drought indices) were obtained from trees in 194 sites covering the species’ geographic ranges and reflecting local environmental gradients. Conclusion: The GenTree Platform is a new resource for investigating ecological and evolutionary processes in forest trees. The coherent phenotyping and environmental characterization across 12 species in their European ranges allow for a wide range of analyses from forest ecologists, conservationists, and macro-ecologists. Also, the data here presented can be linked to the GenTree Dendroecological collection, the GenTree Leaf Trait collection, and the GenTree Genomic collection presented elsewhere, which together build the largest evolutionary forest ecology data collection available

Competition along productivity gradients: news from heathlands

International audienceThe importance of competition in low productive habitats is still debated. Studies which simultaneously evaluate preemption of resources and consequences for population dynamics are needed for a comprehensive view of competitive outcomes. We cultivated two emblematic species of European heathlands (Calluna vulgaris and Molinia caerulea) in a nursery for 2 years at two fertility levels, reproducing the productivity gradient found in phosphorus (P)-depleted heathlands in southwest France. The second year, we planted Ulex europaeus seedlings, a ubiquitous heathland species, under the cover of the two species to evaluate its ability to regenerate. Half of the seedlings were placed in tubes for exclusion of competitor roots. We measured the development of the competitors aboveground and belowground and their interception of resources (light, water, inorganic P). Ulex seedlings' growth and survival were also measured. Our results on resources interception were consistent with species distribution in heathlands. Molinia, which dominates rich heathlands, was the strongest competitor for light and water in the rich soil. Calluna, which dominates poor heathlands, increased its root allocation in the poor soil, decreasing water and inorganic P availability. However, the impact of total competition and root competition on Ulex seedlings decreased in the poor soil. Other mechanisms, especially decrease of water stress under neighbouring plant cover, appeared to have more influence on the seedlings' response. We found no formal contradiction between Tilman and Grime's theories. Root competition has a primary role in acquisition of soil resources in poor habitats. However, the importance of competition decreases with decreasing fertility

Understorey-overstorey biotic and nutrient interactions are key factors for Pinus pinaster growth and development under oligotrophic conditions

The main objective of this study was to examine the interactive effects of nutrient availability and understorey plants, including a nitrogen(N)-fixing shrub, on growth, physiology and survival of commercial maritime pines (Pinus pinaster Ait.). Three experimental sites within the Landes de Gascogne forest were installed in two wet moorlands (one dominated by gorse, a leguminous shrub and one by a perennial grass), and in one dry moorland dominated by ericaceous plants. In dry moorland, the ericaceous understorey increased pine mortality and decreased pine growth, suggesting a competition for water, the most limiting resource of this ecosystem. In wet moorland, a decrease in pine growth suggested a strong competition for soil resources, with or without phosphorus addition. In the other wet moorland dominated by gorse, pines responded to competition for light through stem elongation and self-pruning, but not by reducing growth. The intercropped gorse improved pine N-nutrition and trees acclimated to shrubs by growing more fine roots. Gorse had a positive effect on stomatal conductance during spring, while pine water status decreased moderately with increasing shrub competition during summer. Our results provide new understanding of the feasibility of using gorse as an intercropping N-fixing plant in managed forests, and revealed the structural and physiological trade-offs that exist between increasing N-availability and competition for water and light

A field experiment to study the aerial and root architecture of Pinus pinaster saplings in response to water stress

International audienc

A field experiment to study the phenotypic plasticity of maritime pine saplings (Pinus pinaster aiton) to water stress

In a context of climate change, adaptation of perennial plantations to water constraints becomes a major concern for wood production. Projections point towards more extreme precipitation regimes coupled with more intense, more frequent and longer lasting heat waves inducing frequent and severe droughts. During two years, phenotypic plasticity of Pinus pinaster Ait. to water availability was quantified in the field by planting 1-year-old seedlings under a greenhouse, open at its borders, for rainwater exclusion. Water was provided to re-supply evapo-transpiration losses to half the plants by aerial irrigation. One well growing and one slow growing half-sib families, both of the local improved provenance were compared. The soil water content, water table level, air temperature and humidity were monitored. Shallow soil water content decreased to 6% in the dry treatment in late summer. Predawn leaf water potential was regularly measured and reached -1.37 MPa in the dry treatment/slow-growth family (versus -0.2 in the irrigated treatment) at the end of experiment. After measuring height and diameter (3 times per year in March, July and September 2008 and 2009), 40 to 70 saplings were uprooted for aerial and root biomass and architecture assessment. At the two last sampling times, architecture was measured by 3D digitizing which allowed precise numeric representation of the geometry and topology. Each plant was digitized in two multiscale tree graphs (MTG) of the aerial and root architecture. Several characteristics of architecture were extracted by queries including root/branch number, length, diameter, volume, spatial position, ramification order, branching angle and length of interlaterals. Surprisingly, after the first year of the experiment, water shortage did not affect total biomass of the saplings. However, the water stressed trees had slimmer stems, more biomass allocation to needles (+18%), and distinctly less allocation to roots (-30%), especially distal roots. After two years, the improved saplings in the dry treatment were less tapered. An increase of diameter growth was observed only at the end of the second year of the experiment. We hypothesize that Pinus pinaster saplings stop root growth when the soil is too dry, but maintain their productivity by setting more needles

A field experiment to study the phenotypic plasticity of maritime pine saplings (Pinus pinaster aiton) to water stress

In a context of climate change, adaptation of perennial plantations to water constraints becomes a major concern for wood production. Projections point towards more extreme precipitation regimes coupled with more intense, more frequent and longer lasting heat waves inducing frequent and severe droughts. During two years, phenotypic plasticity of Pinus pinaster Ait. to water availability was quantified in the field by planting 1-year-old seedlings under a greenhouse, open at its borders, for rainwater exclusion. Water was provided to re-supply evapo-transpiration losses to half the plants by aerial irrigation. One well growing and one slow growing half-sib families, both of the local improved provenance were compared. The soil water content, water table level, air temperature and humidity were monitored. Shallow soil water content decreased to 6% in the dry treatment in late summer. Predawn leaf water potential was regularly measured and reached -1.37 MPa in the dry treatment/slow-growth family (versus -0.2 in the irrigated treatment) at the end of experiment. After measuring height and diameter (3 times per year in March, July and September 2008 and 2009), 40 to 70 saplings were uprooted for aerial and root biomass and architecture assessment. At the two last sampling times, architecture was measured by 3D digitizing which allowed precise numeric representation of the geometry and topology. Each plant was digitized in two multiscale tree graphs (MTG) of the aerial and root architecture. Several characteristics of architecture were extracted by queries including root/branch number, length, diameter, volume, spatial position, ramification order, branching angle and length of interlaterals. Surprisingly, after the first year of the experiment, water shortage did not affect total biomass of the saplings. However, the water stressed trees had slimmer stems, more biomass allocation to needles (+18%), and distinctly less allocation to roots (-30%), especially distal roots. After two years, the improved saplings in the dry treatment were less tapered. An increase of diameter growth was observed only at the end of the second year of the experiment. We hypothesize that Pinus pinaster saplings stop root growth when the soil is too dry, but maintain their productivity by setting more needles

The GenTree Leaf Collection: Inter‐ and intraspecific leaf variation in seven forest tree species in Europe

Trait variation within species can reveal plastic and/or genetic responses to environmental gradients, and may indicate where local adaptation has occurred. Here, we present a dataset of rangewide variation in leaf traits from seven of the most ecologically and economically important tree species in Europe. Sample collection and trait assessment are embedded in the GenTree project (EU-Horizon 2020), which aims at characterizing the genetic and phenotypic variability of forest tree species to optimize the management and sustainable use of forest genetic resources. Our dataset captures substantial intra- and interspecific leaf phenotypic variability, and provides valuable information for studying the relationship between ecosystem functioning and trait variability of individuals, and the response and resilience of species to environmental changes.Optimising the management and sustainable use of forest genetic resources in Europ

The GenTree Leaf Collection: Inter‐ and intraspecific leaf variation in seven forest tree species in Europe

Trait variation within species can reveal plastic and/or genetic responses to environmental gradients, and may indicate where local adaptation has occurred. Here, we present a dataset of rangewide variation in leaf traits from seven of the most ecologically and economically important tree species in Europe. Sample collection and trait assessment are embedded in the GenTree project (EU-Horizon 2020), which aims at characterizing the genetic and phenotypic variability of forest tree species to optimize the management and sustainable use of forest genetic resources. Our dataset captures substantial intra- and interspecific leaf phenotypic variability, and provides valuable information for studying the relationship between ecosystem functioning and trait variability of individuals, and the response and resilience of species to environmental changes.Optimising the management and sustainable use of forest genetic resources in Europ