Pollination Ecology and Breeding System of Delphinium Occidentale

Delphinium occidentale Nutt. (Ranunculaceae), the tall larkspur, occurs sporatically as isolated local populations in moist locations at lower and middle elevations of Grand Teton National Park. Individual plants of this species exhibit flowers which occur as one of three distinct color morphs and which occur mixed in the local populations. The three floral morphs are 1) plants exhibiting the most familiar, uniformly dark purple pigmented flower form, 2) plants exhibiting an all white, nonpigmented, albino form, and 3) plants whose flowers are intermediate in form between the extremes of 1) and 2), a semi-albino form which exhibits normally pigmented petals, but white, nonpigmented sepals. The occurrence of mixed, polymorphic populations of D. occidentale floral morphs can be rationalized by two alternative hypotheses: 1. A stable, balanced polymorphism exists among the three morphs. This polymorphism is actively maintained by selective pressures, probably on some aspect of the reproductive biology (perhaps pollination ecology) of the floral morphs, or 2. The distribution of polymorphs is merely a founder effect, reflecting the distribution of morphs present in the seed collection which initially established the colonizing population. The research undertaken during 1993 represents an effort to discriminate between these alternative explanations of flower color polymorphism in D. occidentale