Two subspecies of common reed (Phragmites australis; Poaceae) exist in northern North America: the native P. australis subsp. americanus and the introduced P. australis subsp. australis. There are numerous native populations in Wisconsin, in addition to the more recently established populations of the introduced subspecies. We studied populations of both P. australis subspecies across Wisconsin in order to characterize the genetic diversity of both subspecies and to investigate whether any instances of hybridization could be ascertained in Wisconsin. Using eight microsatellite markers, we found minimal overlap in the alleles that could be recovered from native and introduced plants, and we found no evidence to suggest hybridization between subspecies, even in localities where native and introduced plants grow in close proximity. Overall, we found greater genetic variation in plants of the introduced subspecies relative to the native subspecies, and we observed some geographic patterns of allelic diversity.
Keywords: Common reed; Genetic diversity; Microsatellites; Phragmites australis; Population genetics.