Concepts of Rarity in Vascular Plant Species, With Special Reference to the Genus Calochortus Pursh (Liliaceae)

Summary The concept of rarity in vascular plant species since the mid‐nineteenth century is reviewed with the purpose of illustrating the history of ideas about rare plant taxa. Because much of the more recent literature concerning rare plants focuses rather specifically on isolated features of individual species, a “synthetic approach” incorporating several relevant causes and consequences of rarity in the genus Calochortus is presented. The results of this early synthesis serve to demonstrate the inadequacy of earlier generalizing hypotheses about rarity, and the need for the clarification of both the causes and consequences of rare plants, as well as the frame of reference.