Using a genomic offset approach to guide assisted gene flow in the South American conifer Araucaria araucana

Given the steady decline in the genetic health of tree species populations as adaptation is being outpaced by the speed of human-induced climate change, forest management measures are urgently required. In this context, human translocation of pre-adapted genotypes from source populations whose current climatic conditions are closer to those that recipient populations will experience in the future, the so-called Assisted Gene Flow (AGF), has the potential to reduce the risk of maladaptation and to make more resilient communities. Here, we introduce a metric we call the Mean Offset Ratio (MOR), which is a population pre-adaption measurement useful for AGF as it aims to increase adaptive genetic variation and decrease the risk in maladaptation of recipient populations. We applied MOR to the iconic South American conifer Araucaria araucana and found that populations having the highest risk of maladaptation in the southern Andean piedmonts could benefit from the introduction of genotypes coming from the northern higher elevation Andean populations, which are at the lowest risk of maladaptation. For one metapopulation (Coastal), no translocation possibilities were observed, both as donor and recipient populations. Despite some limitations, we assert that MOR is a useful tool for AGF purposes and could be applied to other tree species. This is the first study to use a genomic approach to inform adaptive forest management actions such as AGF in a long-lived and endangered South American conifer in the face of ongoing climate change.