Reproduction in a Great Basin evening primrose, Camissonia tanacetifolia (Onagraceae) [Xenogamy; California]

Reproductive characteristics of Camissonia tanacetifolia (Onagraceae) in the Great Basin of northeast California were studied in 1978. Manipulations of flowers show xenogamy, an outcrossing breeding system. Additional data include floral morphology, pollen-ovule (P/O) ratio, nectar production, and diversity of insect visitors. The low P/O ratio of 160:1 is atypical of xenogamy. Reproductive proficiency in this xenogamous species with a low P/O ratio may be explained by the viscin threads, which loosely bind pollen together and promote efficiency of pollen transfer, and by its occurrence in open or disturbed habitats. Reproductive potential was also projected for the population from counts of ripe seeds per capsule, capsules per plant, and plant density.