Caroline Scotti-Saintagne

Intraspecific 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. We 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. Hydraulic 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. Overall, 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.

Aim: To reconstruct the colonisation dynamics of silver fir in the Pyrenees during the Holocene using genetic and paleoecological data. Location: Abies alba forests in the Pyrenees and Northeastern Iberia. Taxon: Silver fir ( Abies alba Mill.). Methods: Palaeoecological data from 43 pollen diagrams were used to elucidate the appearance and persistence of silver fir during the Holocene. Additionally, 43 forests were sampled in the southern Pyrenees to perform genetic analyses using 65 SNPs derived from a total of 273 SNPs sourced from a transcriptome assembly. Linear regressions of pairwise population statistics ( F _ST ) against geographical distances were performed to examine the presence of isolation by distance. An assumption‐free approach was also employed to explore the genetic structure of the populations and coalescence analyses were carried out to infer past demography history. Results: We identified Pyrenean eastern and western genetic groups, which originated from an ancestral population located in the eastern Pyrenees. From this population, a westward colonisation took place, during which isolation by distance led to genetic divergence among populations. The eastern group diverged from a common ancestor shared with Alpine populations approximately 110,250 years (3150 generations) ago. The divergence between the eastern and western groups began around 40,250 years ago, coinciding with a reduction in effective population size to 1/2 of its ancestral value. Subsequently, a secondary contact occurred approximately 8575 years ago, resulting in admixed populations in the central Pyrenees. Main Conclusions: We identified a single eastern origin for Pyrenean silver fir populations, followed by westward expansion and spatial differentiation, with recent gene flow between previously isolated genetic groups. This scenario aligns with palaeoecological evidence and shows how the Pyrenees acted as a longitudinal corridor for postglacial colonisation. The resilience and genetic diversity of Pyrenean silver fir populations underscore their importance for the conservation of the species in Europe.

Forestry industry requires high-quantity and quality seeds for afforestation and assisted migration programs. Finding reliable non-destructive methods to characterize seeds would significantly enhance efforts to identify climate-adapted populations. This study presents near-infrared (NIR) spectroscopy models to classify seed origin and predict germination characteristics at different temperatures non-destructively. We focus on Abies alba Mill., a key European forest tree with genetic variation along climatic gradients and seeds with shallow physiological dormancy. Seeds from six populations were analyzed using NIR spectroscopy, and germination was tested at 15°C, 20°C, and 25°C after stratification treatments at 4°C (0 or 3 weeks). Population classification accuracy using Partial Least Squares Discriminant Analysis was 69%, with significant NIR peaks at 1712, 1929, and 2111 nm, linked to moisture content and storage compounds. NIR spectra explained 51% and 65% of the variation in germination probability and timing using Partial Least Squares Regression, with significant peaks at 1712, 1929, 2111, 1632, and 2073 nm. General Linear Mixed-Effects Models showed that a NIR predictor contributed to 39% of the germination probability variance explained by fixed-effects, and the stratification treatment was the most important driver explaining germination time. Our results proved the utility of NIR-based tools to effectively classify bulked seeds and predict germination, opening new perspectives to nursery and forestry sectors and populations’ adaptation and adjustments to warming climate. This study will facilitate further investigations on the physiological processes that occur during dormancy, a critical process for forest regeneration given the expected impact of shorter and warmer winters on seed behavior.

Key message: Phenology is of increasing interest to climate change science and adaptation ecology. Here, we provide bud development, leafing, and leaf senescence data, collected on 772 European beech and silver fir trees between 2006 and 2019 on Mont Ventoux, France. Dataset access is at https://doi.org/10.15454/TRFMZN. Associated metadata are available at https://metadata-afs.nancy.inra.fr/geonetwork/srv/fre/catalog.search#/metadata/a33c8375-9a90-4bc3-a0d7-19317160b68f.

Purpose of Review: Recognizing that in the context of global change, tree genetic diversity represents a crucial resource for future forest adaptation, we review and highlight the major forest genetics research achievements of the past decades in biodiversity-rich countries of the Mediterranean region. For this, we conducted a bibliometric analysis of the scientific literature spanning the past thirty years (1991–2020). Putting together the representative regionwide expertise of our co-authorship, we propose research perspectives for the next decade. Recent Findings: Forest genetics research in Mediterranean countries is organized into three different scientific domains of unequal importance. The domain “Population diversity and Differentiation” related to over 62% of all publications of the period, the domain “Environmental conditions, growth and stress response” to almost 23%, and the domain “Phylogeography” to almost 15%. Citation rate was trending the opposite way, indicating a strong and sustained interest in phylogeography and a rising interest for genetics research related to climate change and drought resistance. The share of publications from Asia and Africa to the total within the Mediterranean increased significantly during the 30-year period analyzed, reaching just below 30% during the last decade. Summary: Describing poorly known species and populations, including marginal populations, using the full potential of genomic methods, testing adaptation in common gardens, and modeling adaptive capacity to build reliable scenarios for forest management remain strategic research priorities. Delineating areas of high and low genetic diversity, for conservation and restoration, respectively, is needed. Joining forces between forest management and forest research, sharing data, experience, and knowledge within and among countries will have to progress significantly, e.g., to assess the potential of Mediterranean genetic resources as assisted migration material worldwide. Introductory quote: Let us collect with care the facts we can observe, let us consult experience wherever we can, and when this experience is inaccessible to us, let us assemble all the inductions which observation of facts analogous to those which escape us can furnish and let us assert nothing categorically; in this way, we shall be able little by little to discover the causes of a multitude of natural phenomena, and, perhaps, even of phenomena which seem the most incomprehensible... J.B. de Lamarck (Philosophie zoologique, 1809), cited by O. Langlet (1971).

Trees are characterized by the large number of seeds they produce. Although most of those seeds will never germinate, plenty will. Of those which germinate, many die young, and eventually, only a minute fraction will grow to adult stage and reproduce. Is this just a random process? Do variations in germination and survival at very young stages rely on variations in adaptations to microgeographic heterogeneity? and do these processes matter at all in determining tree species distribution and abundance?We have studied these questions with the Neotropical Symphonia tree species. In the Guiana shield, Symphonia are represented by at least two sympatric taxa or ecotypes, Symphonia globulifera found almost exclusively in bottomlands, and a yet undescribed more generalist taxon/ecotype, Symphonia sp1. A reciprocal transplantation experiment (510 seeds, 16 conditions) was set up and followed over the course of 6 years to evaluate the survival and performance of individuals from different ecotypes and provenances.Germination, survival, growth, and herbivory showed signs of local adaptation, with some combinations of ecotypes and provenances growing faster and surviving better in their own habitat or provenance region. S. globulifera was strongly penalized when planted outside its home habitat but showed the fastest growth rates when planted in its home habitat, suggesting it is a specialist of a high‐risk high‐gain strategy. Conversely, S. sp1 behaved as a generalist, performing well in a variety of environments.The differential performance of seeds and seedlings in the different habitats matches the known distribution of both ecotypes, indicating that environmental filtering at the very early stages can be a key determinant of tree species distributions, even at the microgeographic level and among very closely related taxa. Furthermore, such differential performance also contributes to explain, in part, the maintenance of the different Symphonia ecotypes living in intimate sympatry despite occasional gene flow.