Understanding the processes influencing the formation and maintenance of species is a central goal of evolutionary biology and crucial to species management in a rapidly changing environment. As such, hybridization and hybrid formation have long been of interest, and recent advances in population-scale genome sequencing have revolutionized our understanding of the frequency and pervasiveness of hybridization in nature. Natural hybrid zones exist across taxonomic groups; however, they are particularly prevalent among forest tree species. While the long generation times and sessile nature of forest trees challenges sufficient tracking of climate through dispersal and migration, introgression of genetic variation via hybridization may be a more general mechanism trees rely on for adaptation to rapidly changing climate. I describe an active hybrid zone for two poplar species, Populus trichocarpa and P. balsamifera, along the Rocky Mountains in northwestern North America. I use a multidisciplinary approach to quantify contributions of climate, geography, and gene flow to divergence and then illustrate how fine-scale assessments of genomic differentiation can elucidate which genomic regions are porous to introgression. I relate these findings to other examples in the literature, contextualize hybridization extent and dynamics under future climate projections, and emphasize the importance of natural hybrid zones to conservation and management.
About the Speaker:
Dr. Connie Bolte is a Postdoctoral Scholar for Dr. Jill Hamilton in the Schatz Center for Tree Molecular Genetics. She earned her doctorate at Virginia Commonwealth University in Integrative Life Sciences where she studied niche dynamics, hybridization, and speciation for eastern North American pine trees. While forest trees remain her focal taxa, the methods Dr. Bolte employs are useful to studying the mechanisms and drivers of evolution within and across any taxonomic group.