Molecular patterns of adaptive variation in spruces

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Boreal spruces are among living organisms with the largest natural distributions. They are generally characterized by high genetic diversity and large population size. These species have only recently re-integrated their ranges following the retreat of glaciers. In contrast, subtropical spruces have much smaller distribution ranges and their occurrence is limited to areas of high altitude. They generally harbor reduced genetic diversity and have suffered an on-going range contraction with the Holocene warming. However, it is not clear if such differences would be reflected at the level of adaptive genetic variation, given that similar adaptations might have evolved to survive colder climates at higher elevations in the south or at northern latitudes. The goal of our research program is to decipher the architecture of adaptation at the molecular level in long-lived undomesticated organisms such as conifers. One major aim is to identify genes harboring adaptive genetic variation and evaluate how patterns of adaptive variation are correlated among spruces. A main obstacle in population genetics of undomesticated plant species is the general lack of molecular genetic markers related to adaptation or other important quantitative traits. Recently, we have shown that it was possible to identify gene polymorphisms (SNPs) potentially involved in adaptive genetic variation, using outlier identification scans of the genome implicating hundreds of genes. Based on these results, range-wide patterns of variation for adaptive outlier SNPs will be investigated. Selection signatures will further be screened in spruce gene families with recent duplicates. A homeologous set of genes spanning the genome will be sequenced in different spruce species to determine their coefficient of molecular adaptation. This research program should result in new genetic markers allowing to monitor adaptive gene variation across spruce genetic landscapes. These markers will allow to estimate the overlap in adaptive gene content among different species and better understand the dynamics of adaptation at the gene level. They will allow to better monitor adaptive genetic resources, which is becoming an urgent task, particularly for endangered subtropical species.