Very Low Genetic Heterozygosities in Sexual and Agamospermous Populations of Eupatorium altissimum (Asteraceae)

An electrophoretic study revealed very low genetic heterozygosities for both sexual and agamospermous populations of Eupatorium altissimum in eastern North America. Low heterozygosity or gene diversity (HT = 0.03) can be explained by the small sizes of the extant sexual populations, estimated to be on the order of 104 . There was no substantial difference in observed heterozygosity between sexual and agamospermous races. This result shows that a higher level of heterozygosity is not a prerequisite for the evolution of agamospermous races from the sexual ancestor.