M.A. Baker & M.A. Cloud-Hughes. 2014. Madroño 61(2): 231-243.
What is Cylindropuntia chuckwallensis?
Cylindropuntia chuckwallensis is a recently described cholla which is endemic to California and ranges from southern San Bernardino County to northern Imperial County. The specific epithet refers to the species’ center of distribution in the Chuckwalla Mountains of Riverside County.
C. chuckwallensis occurs between approximately 400 to 1600 m elevation in creosote scrub on a variety of substrates and soil textures. C. chuckwallensis is generally decumbent to erect, with older plants often having an accumulation of grey, dead material around the base. The plants are usually densely branched and grow to approximately 1 m tall by 2 m wide. Terminal stem segments average 6 cm long by 2 cm wide, with an average of 15 spines per areole. C. chuckwallensis is hexaploid (2n = 66).
The flowers of C. chuckwallensis range from yellow-green (~13% of individuals) to orange (~54%) to dark red-purple (~33%). The styles and filaments range from very light pink to dark red, with the color of the style and filaments generally being proportional to the color of the tepals, i.e. darker flowers having darker styles and filaments. The fruits of C. chuckwallensis are obovate to suborbicular, dry, and spiny.
C. chuckwallensis is both hexaploid (2n = 66) and gynodioecious, with approximately 62% of individuals producing perfect flowers (functional male and female parts) and 38% of individuals producing pollen-sterile flowers. C. chuckwallensis is one of only four known gynodioecious hexaploid Cylindropuntia species, with the other three being C. wolfii, C. sanfelipensis, and C. calmalliana. Although otherwise morphologically distinct, all four of these species share the yellow to orange to dark red flower color variation, and pink to red styles and filaments.
C. chuckwallensis was collected in the 1920s by multiple prominent California botanists, including Jepson, Peirson, Munz, and Keck. However, it was consistently misidentified as C. echinocarpa, which it strongly resembles except for flower color. The species’ authors undertook a large-scale morphological study to distinguish between C. chuckwallensis, C. echinocarpa, and C. multigeniculata, with C. acanthocarpa as the statistical outgroup. When not in flower, C. chuckwallensis can be distinguished from C. echinocarpa by its shorter internodes, larger number of branches per node, and thinner spines and spines sheaths. This combination of characteristics gives C. chuckwallensis an overall denser, more compact, and whiter appearance than C. echinocarpa.
All photos ©Michelle Cloud-Hughes