European beech (Fagus sylvatica L.) is a keystone forest tree species in Europe with a major ecological, economic, and cultural role. While it is predicted to be negatively affected by climate change, its large ecological amplitude and high levels of genetic diversity may provide substantial adaptive potential. In the proposed project, we want to elucidate the role of structural genetic variation in adaptative differentiation and study the effects of genotype-environment interactions in two parallel common gardens in France and Germany, to support predictions about future performance of beech forest ecosystems. To this end, we first want to generate a beech pangenome. This pangenome will capture genome-wide structural genetic variation, that is large-scale DNA sequence polymorphisms such as insertions or deletions, across the distribution range. For this, we will select, sequence and assemble 24 genetically diverse beech individuals originating from different geographic regions and expressing different phenotypes. Additionally, we will perform drone-based high-throughput phenotyping of adaptive traits, such as leaf phenology, in the two common gardens, which comprise trees from 102 range-wide populations. By mapping resequencing data from 1,000 and 1,800 trees growing in the common gardens in France and Germany, respectively, onto the pangenome, we will be able to perform pan-genome-wide association studies (panGWAS) and pangenomic genotype-environment associations (panGEAs). We will then analyze differential effects of the identified sequence variants under the two naturally contrasting environments. Understanding the extent of these genotype-environment interactions is essential for genomic predictions of tree performance under current and future conditions. Finally, we want to analyze possible site-specific effects of natural selection in a single generation. In conclusion, the proposed project will provide further insights into the genetic basis of adaptative differentiation and future ecosystem stability.

We are currently characterising the Lyons-la-Forêt common garden, belonging to the IUFRO common garden series reported by Robson et al; (2018), in tight colalboration with projects AdaptBeech and FAGRESCUE.
After a spring/summer campaign that allowed us to survey budburst times and make other measurements, as well as to collect about 700 leaf samples for DNA extraction, we are going back to collect 600 cambium saples, to compelte the DNA sample panel and start the genomic characterisation.

In parallel, we're preparing for our first UAV phenological surveys in spring 2026.

Project meetings are regularly held with partners of the Von Thunen Institut in Grosshansdorf, Germany: the first one took place in May 2025 in Grosshansdorf, a new one will take place in February-March 2026, possibly at Lyons-la-Forêt, and an intermediate one (online) will be held in December 2025.