Species Timema cristinae

Timema cristinae Vickery, 1993

Named in honor of UCSB Timema expert Cristina Sandoval, who discovered this species in the mountain chaparral above Santa Barbara as a graduate student, and has been researching it and other Timema for decades since (see article here).

This species comes in a number of color morphs, and also striped or unstriped patterns.

Male terminalia are similar to that of T. californicum, except the sinistral cercus is abruptly widened near its base in T. cristinae.

Range is centered in the Santa Ynez Mountains of Santa Barbara County, CA...from the Figueroa Mountain area in the northwest, to the mountains near Santa Barbara on the east.

On foliage, twigs, or branches of host shrubs in coastal chaparral habitat...or on the ground, where they sometimes shelter or drop to upon disturbance.

Green morphs tend to rest on leaves; brown to gray morphs on stems, branches or ground.

Unstriped morphs are usually associated with broad-leaved host plants (e.g. ceanothus); striped morphs are usually associated with host plants having needle-like leaves (e.g. chamise).

Coloration, stripes, and other markings serve as camouflage, and are adaptations driven by selection pressure due to predation by visually-oriented birds and lizards. For interesting details, see Sandoval (1994), Sandoval & Crespi (2008), and this course handout & worksheet...and other papers cited below under "Print References".

Principle host plants are Adenostoma fasciculatum and Ceanothus spinosus, but it's also been recorded feeding on Heteromeles arbutifolia, Cercocarpus betuloides, Pickeringia montana, Quercus agrifolia, and Peonia californica. It has been observed (not necessarily feeding) on other oaks, and on Arctostaphylos glauca, Ribes malvaceum and Fraxinus dipetala.

This is probably the most thoroughly studied species of Timema, due largely to the work of Cristina Sandoval and other researchers she has collaborated with and/or inspired over the years.

Crespi, B. J. Sandoval, C.P. (2000). Phylogenetic evidence for the evolution of ecological speciation in Timema walking-sticks. Journal of Evolutionary Biology, 13:249-262.

Nosil, P. (2007). Divergent Host Plant Adaptation and Reproductive Isolation Between Ecotypes of Timema cristinae Walking Sticks. The American Naturalist, 169(2) pp. 151-162.

Nosil, P., Crespi, B., and Sandoval, C. (2002). Host-plant adaptation drives the parallel evolution of reproductive isolation. Nature:417:440-443. (Full Text)

Nosil, P., Crespi, B., and Sandoval, C. (2003). Reproductive Isolation driven by the combined effects of ecological adaptation and reinforcement, Proceedings of the Royal Society of London. B, vol. 270, pp. 1911-1918.

Nosil, P., Sandoval, C.P., and Crespi, B. (2006). The evolution of host preference in allopatric vs. parapatric populations of Timema cristinae. Journal of Evolutionary Biology 19:929-942. (Full Text)

Sandoval, C.P. (1993). Geographic, ecological and behavioral factors affecting spatial variation in color morph frequency in the walking-stick, Timema cristinae. PhD thesis, University of California, Santa Barbara, CA

Sandoval, C.P. (1994). Differential visual predation on morphs of Timema cristinae (Phasmatodea, Timemidae) and its consequences for host range. Biol. J. Linn. Soc., 52, pp 341-356.

Sandoval, C. P. and Nosil, P. (2005). Counteracting selective regimes and host preference evolution in ecotypes of two species of walking-sticks. Evolution 59:2405-2413 (Full Text)

Cristina Sandoval's Timema web page : Images of 13 species, research project info, and bibliography...with some articles available as PDF's. [Archived version, original link defunct]

An excellent student-written review article from Lake Forest College, on speciation in T. cristinae

NEWS ITEM! (3/29/18): The Timema Discovery Project is an important new initiative aiming to harness as many people as possible to collect much needed data for advancing our understanding of Timema...please visit the web site, spread the word, and participate!