Abstract
American beachgrass (Calamagrostis breviligulata) builds dunes throughout eastern North America, but the native populations may suffer out-competition from introduced commercial cultivars, including the Cape cultivar. RAD-sequencing of 92 samples revealed three genetic groups designated as Great Lakes (GL), Lake Champlain (LC), and Cape Group (CG). CG included the known Cape cultivar and other commercial samples, while GL and LC represent the native samples. GL and LC flowered earlier in the season compared to CG, and while both also have shorter panicles than CG, those of GL are longer than LC. Genetic distinctiveness of the Champlain beachgrass provides justification for its subspecies classification as Calamagrostis breviligulata ssp. champlainensis. Restored Lake Ontario dunes supported higher arbuscular mycorrhizae (AMF) richness than unrestored dunes. Under greenhouse conditions, GL seedlings grew larger than LC seedlings, regardless of AMF inoculum source. This thesis supports major shifts on plant materials used for restoration and genetic diversity conservation.