Gender dimorphism has evolved at least twice in the Solanaceous genus Lycium. In the North American dimorphic species, male-sterile plants (i.e., females) have flowers with a long style equal to or slightly exserted from the corolla tube and abortive anthers, while perfect-flowered plants (i.e., hermaphrodites) have a style of variable length with a set of long, fertile anthers equal to or exserted from the mouth of the corolla tube. Several important characters associated with the evolution of gender dimorphism are highlighted and discussed in the context of the evolution of gender dimorphism. In this group, polyploidy appears to have triggered the evolution of gender dimorphism by disrupting the self-incompatibility system, leading to inbreeding depression and invasion by male-sterile mutants.

Key words: gender dimorphism, gynodioecy, Lycium, polyploidy, self-incompatibility, Solanaceae