Extensive chloroplast introgression has been documented in polyploid Betula species of eastern North America. However, the extent to which the nuclear genomes of these species are differentiated is unknown. Therefore, we evaluated genetic differentiation among largely sympatric Betula papyrifera, B. alleghaniensis, and B. lenta using nuclear microsatellite markers. Principal components analysis (PCA) and analysis of molecular variation (AMOVA) were used to evaluate genetic differentiation. Bayesian model-based clustering was used to identify putatively admixed individuals. Despite...