Hedging at the rear edge: Intraspecific trait variability drives the trajectory of marginal populations in a widespread boreal tree species

Rear-edge populations at the warm margin of species distribution are small, isolated and face environmental conditions at the limit of species bioclimatic envelope. Intraspecific phenotypic variation contributing to the persistence of peripheral populations is expected to become increasingly important under future climate conditions in order to avoid local extirpation where range shifts lag behind climate change velocity. We investigated the putative role of intraspecific phenotypic variation for the maintenance of rear-edge populations of fire-prone jack pine (Pinus banksiana), an obligate pyriscent boreal species. We assessed whether variation in cone serotiny is associated with the population trajectory of marginal stands located south of the boreal biome, in the temperate forest where natural wildfires are infrequent and unpredictable. To this end, we estimated stand-scale serotiny, minimal age and tree size structure in 26 jack pine stands from the rear edge (n = 17 sites) and the ...