Evidence is accumulating worldwide about the detrimental effects of climate change (CC) on forest viability. Among the main causes of reduced fitness and augmented mortality is the insurgence of maladaptation between the current genetic make-up of tree populations and the newly established climatic conditions (e.g., increase in temperature and drought). Disruption in local adaptation has been observed in several species, which can concur in boosting genetic erosion and local extirpation especially when phenotypic plasticity is not sufficient to tolerate the newly established climatic conditions, adaptation is incompatible with the rate of environmental change, adaptive gene flow is inadequate to compensate for maladaptation, and human disturbance acts in synergy with CC through habitat degradation.
The conservation of extant forest genomic resources (FGRs) has been recognized by the post-2020 global biodiversity framework as the warranty for tree populations to maintain sufficient adaptive potential in the face of CC. To this aim, both genome-wide and functional variation are to be characterized and included into conservation strategies, the former being a potential reservoir for future adaptation, the latter underlying local adaptations towards past and current conditions. Strategies for evolutionary rescue include to prioritize genetically diverse and differentiated populations and to promote ad hoc translocations of maladapted populations towards newly suitable sites (i.e., assisted migration).
The project MedForAct aims to provide forest professionals with genomic-informed guidelines for the conservation and management of FGRs in the Mediterranean Region, a hotspot of climate change. By relying on a pilot framework composed by three indigenous pines (Pinus halepensis, P. pinaster and P. pinea) and an extensive climatic and genetic sampling along the Italian peninsula, MedForAct aims to:
Identify functional variation that fostered convergent local adaptation despite about 33 Myr of independent evolution in the dynamic geoclimatic context that shaped the Mediterranean climate (Thompson 2020; Jin et al. 2021);
Devise a novel application for assisted migration and (re)forestation that minimizes maladaptation throughout a network of optimal genetic exchange between tree populations.
Adaptive gene flow is expected to produce a 10% increase in survival provided the frequency of an adaptive allele is augmented by nearly 50% in a target population (Jaramillo-Correa et al. 2015). Consequently, the project will contribute preserving key ecosystem services provided by Mediterranean pine forests like carbon sequestration, soil and coast protection against erosion and salt spray, water filtration, food, as well as areas for recreation, provided that actions are put in place which account for genomic information.
Jaramillo-Correa, J. P., Rodríguez-Quilón, I., Grivet, D., Lepoittevin, C., Sebastiani, F., Heuertz, M., ... & González-Martínez, S. C. (2015). Molecular proxies for climate maladaptation in a long-lived tree (Pinus pinaster Aiton, Pinaceae). Genetics, 199(3), 793-807.
Jin, W. T., Gernandt, D. S., Wehenkel, C., Xia, X. M., Wei, X. X., & Wang, X. Q. (2021). Phylogenomic and ecological analyses reveal the spatiotemporal evolution of global pines. Proceedings of the National Academy of Sciences, 118(20), e2022302118.
Thompson, J. D. (2020). Plant evolution in the Mediterranean: insights for conservation. Oxford University Press, USA.