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Conservation status

Juniperus poblana

(Martínez) R.P. Adams 2006

Common names

Pueblo juniper, poblana juniper (Adams et al. 2006).

Taxonomic notes

From the mid-1900s to 2006, this taxon was generally known as Juniperus flaccida var. poblana Martínez. In 2006, RAPD sequencing for the three generally recognized varieties of J. flaccida revealed it to be polyphyletic, and each variety was then elevated to species rank. The analysis of Adams et al. (2006) found it to be sister to J. standleyi and to a clade including J. monticola, J. jaliscana, J. durangensis, and the other two varieties of J. flaccida (now described as J. flaccida s.s. and J. martinezii); the authors also provide detailed discussion of the historical changes in taxonomic thinking about this group of species. One variety has been described, J. poblana var. decurrens R. P. Adams, which can be distinguished using morphological characters as well as by its DNA and essential oil composition (Adams and Schwarzbach 2015).

Synonymy (for the species):

Type: Mexico, Puebla: Amozoc at 2300 m, Martínez 507 (Holotype: MEXU!).

Description

Dioecious trees up to 8 m tall, usually with a forked trunk and globose crown. Bark on branchlets (5-10 mm diameter) is smooth; on larger branches and stems brown, exfoliating in wide strips. Branches are erect, but flaccid at the tips, so that the tree retains a "drooping" character in comparison with most other Mexican junipers; branches are planate (fan-shaped). Both scale and decurrent leaves are conspicuous, the scale leaves on ultimate twigs with sharp, acute, divergent tips (appearing decurrent). Seed cones are glaucous, blue-brown, 9-12 mm in diameter; the mature cones usually show suture lines from fusion of the cone-scales, thus resembling a soccer ball. There are (4-)6-10(-13) seeds per cone, each 5-6 mm long. Pollen is shed in the spring (Adams 2004, Adams et al. 2006).

The species closely resembles J. martinezii and J. flaccida. Adams and Schwarzbach (2015) present the following key to separate the species in this group:

1.

Seed cones large, 9-17 mm diam., (4-) 6-10 (-13) seeds per cone, terminal branch tips drooping (hanging)

 

2

2.

Seed cones 9 - 20 mm diam., with (4-) 6-10 (-13) seeds, foliage weeping

 

J. poblana var. poblana

2.

Foliage weeping, branching radially, seed cones brownish-purple, tan-brown

 

3

3.

All leaves decurrent, with free tips, foliage very weeping, bark exfoliating in thin, scaly, plates

 

J. poblana var. decurrens

3.

Leaves decurrent with mostly appressed tips, foliage weeping, bark exfoliating in thick, interlaced stripes

 

J. flaccida

1.

Seed cones small, (5-)6(-9) mm diam., 1-2(-3) seeds per cone, terminal branch tips erect

 

J. martinezii

Distribution and Ecology

Mexico: Distrito Federal, Guerrero, Hidalgo, Jalisco, México, Morelos, Oaxaca, and Puebla; and perhaps intervening areas. Found on dry, calcareous slopes, in pure stands or in mixed forests, at 1200-2300 m elevation; uncommon, but usually abundant where it occurs (Zanoni and Adams 1979). Hardy to Zone 8 (cold hardiness limit between -12.1°C and -6.7°C) (Bannister and Neuner 2001).

Distribution data from USGS (1999). This map is based on a prior map of J. flaccida sensu lato limited to the provinces where J. poblana is known to occur, and also as modified in accordance with the distribution map of Adams (2004).

Conservation status is somewhat unclear. The species is probably sufficiently widespread and common to be at low risk of extinction, but most herbarium specimens predate the 2006 recognition of polyphyletic varieties in J. flaccida, so its actual distribution requires detailed re-examination of the older collections. There is a threat from woodland clearing for agriculture and grazing which is likely to cause a decline of the population (Farjon 2013).

Big tree

Oldest

Dendrochronology

Ethnobotany

Observations

Remarks

Citations

Adams, Robert P. 2004. Junipers of the World: The Genus Juniperus. Trafford Publishing.
Brief versions of the descriptions are available online at www.juniperus.org.

Adams, R. P., J. A. Perez de la Rosa and M. Charzaro. 1990. The leaf oil of Juniperus martinezii Perez de la Rosa and taxonomic status. J. Essential Oil Res. 2:99-104. Available online at juniperus.org.

Adams, R. P., A. E. Schwarzbach and S. Nguyen. 2006. Re-examination of the taxonomy of Juniperus flaccida var. martinezii, and var. poblana (Cupressaceae) Phytologia 88(3):233-241.

Adams, R. P., and A. E. Schwarzbach. 2015. A new, flaccid, decurrent leaf variety of Juniperus poblana from Mexico: J. poblana var. decurrens R. P. Adams & S. González. Phytologia 97(3):152-163.

Farjon, Aljos. 2013. Juniperus flaccida var. poblana. The IUCN Red List of Threatened Species, Version 2015.2. www.iucnredlist.org, accessed 2015.07.28.

See also

Adams, R. P., and T. A. Zanoni. 2015. The volatile leaf oils of Juniperus flaccida Schltdl., J. martinezii Perez de la Rosa and J. poblana (Mart.) R. P. Adams, re-examined. Phytologia 97(2): 145-151.

Farjon (2005) provides a detailed account, with illustrations.

R.P. Adams' web site, juniperus.org.

Vascular Plant Image Gallery.

Last Modified 2017-12-29