Ancient Bottleneck events, spatially heterogeneous selection, purifying selection and increased risk of maladaptation shape the past, present and future population structure of a widespread conifer
Demographic events and selection can shape population structure and adaptation capability to future stressors. We used two range-wide datasets in Ponderosa pine (Pinus ponderosa) to better understand the influences of demography and selection. Samples were sequenced with 55,000 capture-seq probes. We examined current population structure, changes in Ne over time, evidence for selection using genome x environment association methods and future maladaptation risk using genomic offset.We identified four potential varieties within the species, numerous bottleneck events that mirror glacial advances and droughts, the presence of purifying and balancing selection in response to moisture availability, many areas with high amounts of genomic offset Differentiation across varieties has most likely been driven in part by bottleneck events causing random losses of alleles and decreased connectivity. Differentiation due spatially heterogeneous selection and purifying selection in response to varied moisture levels is the other main factor driving population structure. Many areas are predicted to be at risk of future maladaptation, which coincide with previous studies showing mortality events and decreased regeneration. Previous evolutionary events and rapidly changing climate have shaped future maladaptation risk as there are drastic changes from current genomic structure needed to meet a rapidly changing climate