Prof Richard Buggs (@rbuggs.bsky.social)

Genetic basis of traits and local adaptation in UK silver birch Knowledge of the genomic basis of phenotypes in forest trees lags that of other economically important organisms. We sequenced the genomes of 2054 silver birch trees from 20-year-old field trials at three locations in Britain, each site containing trees from the same 29 source populations. Our results lay foundations for genomic source-selection and breeding. We discovered single nucleotide polymorphisms (SNP) associated with tree height, wood density, carbon isotope composition and stem form. Using genome-wide SNP we predicted variation in several phenotypic traits of trees with a similar genetic background and estimated the breeding values of 148 selected plus trees. We identified loci associated with adaptation to source local environments. We used these loci to forecast adaptation to each trial site and future predicted conditions at source. Comparison of these forecasts to phenotypic performance in the trials suggests that genomic forecasts of adaptation to future climates should be interpreted with caution. ### Competing Interest Statement The authors have declared no competing interest. Department for Environment Food and Rural Affairs, https://ror.org/00tnppw48, Center for Forest Protection Grant 2202 Research Council of Finland, 343059 https://www.biorxiv.org/content/10.1101/2025.07.04.662749v1