Hoffman M. T., Functional dioecy in Echinocereus coccineus (Cactaceae): breeding system, sex ratios, and geographic range of floral dimorphism, American Journal of Botany, 1992, 79(12):1382-1388, doi: 10.1002/j.1537-2197.1992.tb13748.x
Field research and controlled pollination in New Mexico demonstrated functional dioecy in the studied Echinocereus coccineus populations. The paper describes differences between male and female flowers, sex ratios, bee visitation and geographic variation in floral dimorphism under the historical circumscription of the species.