Genecology of Holodiscus discolor (Rosaceae) in the Pacific Northwest, USA

An important goal for land managers is the incorporation of appropriate (e.g., locally adapted and genetically diverse) plant materials in restoration and revegetation activities. To identify these materials, researchers need to characterize the variability in essential traits in natural populations and determine how they are related to environmental conditions. This common garden study was implemented to characterize the variability in growth and phenological traits relative to climatic and geographic variables of 39 Holodiscus discolor (Pursh) Maxim. accessions from locations throughout the Pacific Northwest, U.S.A. Principal component analysis of 12 growth and phenological traits explained 48.2% of the observed variability in the first principal component (PC-1). With multiple regressions, PC-1 was compared to environmental values at each source location. Regression analysis identified a four-variable model containing elevation, minimum January temperature, maximum October temperature, and February precipitation that explained 86% of the variability in PC-1 (r2 = 0.86, p < 0.0001). Spatial analysis using this regression model identified patterns of genetic diversity within the Pacific Northwest that can help guide germplasm selection (i.e., seed collections) for restoration and revegetation activities.