There are a number of characteristics which can be summarized regarding the Dudleya genus. Genus occurrences are restricted to southwest North America; in fact, according to Low, approximately 98 percent of genus occurrences are along or near the coasts of Baja California, (the states of Baja Sur and Baja Norte in Mexico), plus the northward extension into the USA in the states of California and southern Oregon. A small number of genus populations are found in Arizona and possibly Nevada. The center of genus diversity is the coastal region where Mexico and the USA meet. Dudleyas have a strong affinity for the coastal regions, but some species have ranges that extend into the nearby mountains and deserts.
Most species of Dudleya grow at elevations near sea level, but a few grow on or even atop mountains of Baja California, the high Sierra Nevada and in many other California mountain ranges. Many, such as D.cymosa, prefer canyon locations on vertical or near vertical rocky walls, often in the shade, surviving in very little soil in the crevices of almost solid rock. Sometimes the occurrences are in locations that receive no direct sunlight. Almost all Dudleya species have succulent leaves arranged into rosettes. Because of this rosette geometry many genus members are striking in their visual appeal. Many, including the Canyon Liveforever, have leaves that are glaucous (covered with a whitish or bluish waxy coating) or frosty looking.
The chromosome count of all Dudleya species is n=17, with about 35% of all populations consisting of polyploids (individuals with multiples of the base number). Remarkably, according to extensive crossing experiments conducted by Verity, all Dudleya taxa are capable of hybridizing in nature.
There are eight recognized subspecies of D. cymosa (flower color in parentheses):
- D. cymosa subsp. agourensis K.M.Nakai: Canyon Liveforever (bright yellow)
- D. cymosa subsp. crebrifolia K.M.Nakai & Verity: San Gabriel River dudleya (mustard yellow)
- D. cymosa subsp. costafolia Bartel & Shevock: Pierpoint Springs Dudleya (bright yellow)
- D. cymosa subsp. cymosa: Canyon Liveforever, the nominate subspecies (bright yellow, red or orange)
- D. cymosa subsp marcescens Moran: Marescent Dudleya (bright yellow with orange or red markings)
- D. cymosa subsp ovatifolia: (Britton) Moran Santa Monica Mountains Dudleya (bright yellow, rarely with red or orange marking)
- D. cymosa subsp. paniculata: (Jeps.) K.M.Nakai (pale yellow-white to pale yellow-pink)
- D. cymosa subsp. pumila: (Rose) K.M.Nakai (bright yellow or red)
- C. Michael Hogan. 2011. ''Dudleya cymosa (Lem.) Britt. & Rose. Encyclopedia of Earth, National Council for Science and the Environment, Washington DC eds. A. Howald & M. McGinley
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