Hybrid zones are often viewed as active sites of evolutionary change, either as sources of new recombinant types, new species, or as regions where species’ barriers may be examined to infer mechanisms of speciation. In forest trees, hybrid zones present natural laboratories to examine the genetic and ecological interactions underlying to adaptation. Indeed, hybrid zones allow us to examine the fine-scale transfer of genetic material between species that may be important in terms of adaptation, as well as identifying regions of the genome contributing to reproductive isolation and the maintenance of species barriers. Ultimately, the genetic analysis of hybrid zones leads to a more mechanistic understanding of the processes involved in the origin of adaptations and the origin of species. In this study, we are examining the respective roles of genomic ancestry, genetic variation, environmental variation, and their interactions to tree fitness. Using wild-collected material from replicated, latitudinally differentiated, natural hybrid zones between Populus trichocarpa x P. balsamifera, in conjunction with modern sequencing, and an extensive network of replicated common gardens we are evaluating the consequences of hybridization to climatic adaptation. Populus provides an ideal model for this work with its compact genomes, rapid clonal growth, ease of vegetative propagation and extensive range of natural genomic and phenotypic variation. Preliminary data suggest that hybridization is a stimulus for novel genomic architectures, but that there is substantial variability in the direction and extent of nuclear and chloroplast introgression across replicate zones of hybridization that may be associated with environmental thresholds. Indeed, genotype response functions across replicated common gardens indicate varying influence of the environment, genomic ancestry, genetic variation, and interactions for phenotypic traits important to adaptation across environments. Overall, these results underscore the value of using natural hybrid zones in a predictive context to understand adaptation needed for forest management in a changing climate.