Department of Botany, Iowa State University, Ames, IA 50011. Sauer, became major weeds. All genetic characterization of Amaranthus has focused exclusively on the monoecious grain amaranths and their weedy progenitors. Isozyme analysis of dioecious species reveals fundamental differences in the genetic structure of populations of monoecious and dioecious species. Monoecious species tend to have very low within population diversity with most individuals fixed for a single allele, indicating high levels of inbreeding.
Dioecious species have high within population diversity reflecting obligate outcrossing.
These species also form a phenetically distinct cluster from the monoecious species.