Periodic Reporting for period 1 - MedForAct (Unveiling convergent adaptation in Mediterranean pines to inform a new tool for the management of forest genomic resources)
Periodo di rendicontazione: 2023-06-01 al 2025-05-31
Evidence of the detrimental effects of climate change (CC) on forest viability is accumulating worldwide. One of the main causes of increased forest mortality is the emergence of maladaptation between the current genetic make-up of tree populations and the newly established climatic conditions. Disruptions in local adaptation have been observed in several species, which can lead to genetic erosion and local extirpation, especially when phenotypic plasticity is insufficient to confer tolerance to the new climatic conditions, the adaptive response is incompatible with the rate of environmental change, gene flow is insufficient to compensate for maladaptation, and human disturbance acts synergistically with CC through habitat degradation. Conservation of existing forest genomic resources (FGRs) has been recognised by the post-2020 global biodiversity framework as a guarantee that tree populations will retain sufficient adaptive potential in the face of CC. To this end, both genome-wide and functional variation need to be characterised and incorporated into conservation strategies, the former as a potential reservoir for future adaptation and the latter as a basis for local adaptation to historical habitat conditions. Strategies for evolutionary rescue include prioritising genetically diverse and differentiated populations and promoting ad hoc translocations of locally adapted populations to newly suitable sites (i.e. assisted migration). Based on the literature, genome-informed assisted migration is expected to result in a 10% increase in survival when the frequency of an adaptive allele is increased by nearly 50% in a target tree population. The MedForAct project aims to provide forest professionals with genome-informed guidelines for the conservation and management of FGRs in the Mediterranean region, a hotspot for forest genetic diversity and climate change. In particular, based on a pilot framework of three native pine species (Pinus halepensis Mill., P. pinaster Aiton and P. pinea L.) and extensive climatic and genetic sampling across the Italian peninsula, MedForAct will 1) identify functional variation that has promoted convergent local adaptation despite about 33 Myr of independent evolution in the dynamic geoclimatic context that has shaped the Mediterranean climate, and 2) develop a novel application for assisted migration that minimises maladaptation through a network of optimal genetic exchange between tree populations. As a result, the project is expected to help maintain key ecosystem services such as carbon sequestration, soil and coastal protection from erosion and salt spray, water filtration, food and recreational areas.
MedForAct field activities resulted in the collection of 966 samples, distributed in 38 populations of Aleppo pine (Pinus halepensis), 23 of Mediterranean pine (Pinus pinaster) and 12 of stone pine (Pinus pinea), which were harmonised with in-house resources from previous and ongoing research projects (https://sites.google.com/view/medforact/sampling(si apre in una nuova finestra)). On average, about 13 samples per population were characterised. All biological samples will be stored for future use in the "BIOMEMORY Network of Biological Collections of the Department of Biology, Agriculture and Food Sciences (DiSBA) of the National Research Council of Italy (CNR)" and thus made openly accessible. Genomic data (already available in the case of P. pinea, and expected by May 2025 in the case of P. halepensis and P. pinaster) are ideal for genetic monitoring, as the type of genotyping used makes them easy to harmonise with existing and new datasets, representing a significant added value for the genetic characterisation of the Italian forest genetic resources (FGRs). Preliminary analyses were performed on the genomic data of P. pinea populations. The results obtained provided important clues as to the origin of the material (local vs. translocated) and, secondly, suggested genetically based criteria for optimising the selection of seed stocks for the Italian network of genetic conservation units (as currently discussed within MedForAct with the competent bodies at regional level). This choice could have important implications for mitigating the effects of climate change on the species. Finally, these Italian populations have become part of a larger European dataset at the scale of the entire range of the species, filling an important gap that will allow refinement of the biogeographic models under discussion. One of the expected outcome is the sharing of knowledge through scientific publications in international peer-reviewed journals.
The fieldwork and genotyping effort carried out in this project represents the largest characterisation of Mediterranean pine species ever undertaken in Italy. This effort has the potential to have a significant impact on the conservation of the genomic resources of Mediterranean pine forests, both nationally and across the range of the species. Genomic analyses of Italian stone pine populations revealed a high degree of genetic structuring and populations with significantly higher levels of diversity than traditionally reported for the species, with ancestral gene pools spatially structured along a latitudinal gradient from northern to southern Italy. This observation is relevant given the expectation of extensive historical translocations and consequent dilution of the signal of geographic genetic structure. Conversely, there is evidence of local origin for the majority of the populations analysed, with the exception of a few samples from southern Italy. These observations pave the way for genomic-driven in situ and ex situ conservation actions. Finally, the analyses carried out on the entire species range seem to confirm the existence of private Italian gene pools, thus excluding the ubiquitous presence of recent translocations.