Adaptive potential and genomic vulnerability of keystone forest tree species to climate change: a case study in Scots pine

Abstract

A better understanding of the possible adaptive response and genomic vulnerability of forest trees is needed to properly assist future forest management and develop adequate resilience strategies to changing environments. Scots pine (Pinus sylvestris L.), a keystone species with extensive distribution and a broad ecological niche, is expected to be directly impacted by climate change due to fitness loss and genetic maladaptation on a large spatial scale. Despite extensive studies that have clarified the broad-scale history and genetic structure of the species, understanding the genetic basis for the local adaptation and genomic vulnerability of Scots pine remains incomplete. Here, we used thousands of genotyped SNP markers in 39 natural populations (440 trees) along a broad latitudinal gradient of species distribution to examine molecular signatures of local adaptation. Specifically, this landscape genomics approach aimed to assess fine-scale patterns of SNPs associated with environmental gradients, predict vulnerability to climate change using genomic offset, and evaluate the adaptive response of populations to projected climate shifts. The variation of outlier SNPs, which exhibits selection signatures between genetically very similar populations in the distribution range, was highly correlated with mean temperature, a key limiting factor for the growth and survival of tree species. Furthermore, our simulation results indicated a high genomic vulnerability on a large spatial scale in P. sylvestris, with the time frame required to close the offset gap by natural selection estimated to be in the range of hundreds of years. The results improve our understanding of Scots pine's adaptive capacity and provide insights for management approaches to mitigate the impacts of climate change on temperate forest ecosystems. By evaluating adaptive responses, the study adds to the discussion on the long-term sustainability of forest ecosystems in the face of ongoing environmental change.