Arizonia juniper (Adams 2008).
Syn: Juniperus coahuilensis (Martínez) Gaussen ex. R.P. Adams var. arizonica R.P. Adams 1994.
Formerly treated within Juniperus coahuilensis, but segregated as a variety on the basis of leaf terpenoid and RAPD analysis showing a strong New Mexico-West Texas gradient in the first principal component of the data set (Adams 1994). Subsequently, nrDNA and trnC-trnD sequence data were found to place J. coahuilensis (type variety) and var. arizonica in separate clades, with arizonica sharing a clade with J. occidentalis and J. osteosperma (Adams et al. 2006). Adams et al. (2006) accordingly elevated the variety to species rank.
Dioecious shrubs or small trees up to 8 m tall, usually with a single stem branching near the ground, with a flattened-globular or irregular crown. Bark at first thin, scaly, ash-gray, becoming brown on larger stems and exfoliating in strips. Bears both decurrent (whip-like) and scale-like leaves. Leaf margins toothed (visible at 20X magnification), adaxial leaf surface glaucous. At least 25% of the whip leaves bear a conspicuous gland with a whitish exudate. Seed cones glaucous, yellow-orange to dark red beneath the glaucous bloom, soft, juicy, globose to ovate, 6-7 mm diameter, with 1(-2) seeds 4-5 mm long. Pollen shed late fall or early winter. Distinguished from J. coahuilensis by having small whip-leaf glands half or less as long as the associated sheath (Adams 2008, Farjon 2010).
US: Arizona, New Mexico; Mexico: Chihuahua, Sonora; at 980-1600(-2200) m elevation; on Bouteloua grasslands and adjacent rocky slopes (Adams 1993, 2008). In Arizona it occurs with J. osteosperma on some sites, or with Opuntia spp. or Yucca spp., but commonly its only associates are grasses, an unusual setting for a conifer. Its persistence in grasslands may be due to its unusual ability to resprout from cut or fire-killed stumps (Farjon 2005, citing pers. comm. from R.P. Adams).
Used for fenceposts; locally regarded as a weed (Adams 2008).
Adams, R. P. 1994. Geographic variation and systematics of monospermous Juniperus from the Chihuahuan desert based on RAPDs and terpenes. Biochem. Syst. Ecol. 22:699-710.
Adams, R. P., S. Nguyen, J. A. Morris and A. E. Schwarzbach. 2006. Re-examination of the taxonomy of the one-seeded, serrate leaf marginated Juniperus of southwestern United States and northern Mexico (Cupressaceae). Phytologia 88(3):299-309.
R.P. Adams' web site, juniperus.org.
Adams, R. P. 2017. Multiple evidences of past evolution are hidden in nrDNA of Juniperus arizonica and J. coahuilensis populations in the trans-Pecos, Texas region. Phytologia 99(1): 38-47.
Last Modified 2017-09-03