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Young tree in the Sierra La Marta, Coahuila [Jeff Bisbee, 2014.09].

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Mature cone, Sierra La Marta, Coahuila [Jeff Bisbee, 2014.09].

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Sun foliage, Sierra La Marta, Coahuila [Jeff Bisbee, 2014.09].

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Twig with foliage, Sierra La Marta, Coahuila [Jeff Bisbee, 2014.09].

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Needles and twigs of a 1.3 m tall sapling in the Seattle arboretum. Image width 10 cm [C.J. Earle].

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Winter buds on a growing tip. Specimen in Seattle arboretum. Image height 4 cm [C.J. Earle].

 

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Conservation status

Picea engelmannii subsp. mexicana

(Martínez) P. Schmidt 1988

Common names

Mexican spruce, Pícea mexicana [Spanish].

Taxonomic notes

Synonymy:

Although often cited as a variety (Taylor and Patterson 1980, Taylor et al. 1994), the substantial difference in climatic adaptation (USDA zone 7, vs. 3-4 in the type), and chemical similarities to P. sitchensis (Taylor et al. 1994) justify the treatment at subspecies rank as proposed by Schmidt (1988). There is also merit in awarding it species rank, as did Ledig et al. (2004), but it would still be recognized as sister to P. engelmannii.

Description

"This ssp. differs from the typical ssp. in its lighter (grey) bark, its narrower leaves (1-1.2 mm) and its narrower and slightly longer bract scales (4-6 mm)" (Farjon 1990). The bract scale measurement is not wholly reliable, as equally long bracts can be found on the typical subspecies, but the cones can be distinguished by their larger mean size (4.5-8 cm, vs. 3-6cm in the type) and slightly larger seed scales, but there is much overlap (cones in collection of M. P. Frankis); see also Taylor et al. (1994).

Distribution and Ecology

Mexico: First found in the Sierra de la Marta, 75 km SE of Saltillo in Nuevo Leon, NE Mexico. It grows on steep, moist, north-facing slopes on soils derived from dolomite, at 3000-3400 m elevation (Farjon 1990). Another population on Cerro Mohinora in S Chihuahua, discussed as uncertain by Taylor and Patterson (1980), has now been assigned to ssp. mexicana (Farjon 1990, Taylor et al. 1994). A third population has been found in the Sierra el Coahuilon, Coahuila. USA: The population of Picea engelmannii in the Chiricahua Mts of Arizona has in the past been referred to this subspecies (Taylor and Patterson 1980: p.438), but molecular analyses presented by Ledig et al. (2004) indicate those trees belong to the type subspecies. USDA hardiness zone 7.

This species (under the name Picea mexicana) is listed as endangered in Mexico under NOM-ECOL-059-94. Although each of the three populations probably contains several thousand trees (Ledig et al. 2000), they are nonetheless widely disjunct and grow on some of the tallest mountains in the region. This taxon warrants treatment as one of the most critically endangered conifers in the world, at high risk of extinction in the foreseeable future due to stressors including climate change and fire.

Big tree

Oldest

Dendrochronology

Ethnobotany

Observations

Remarks

Citations

Ledig, F.T., M. Mápula-Larreta, B. Bermejo-Velazquez, V. Reyes-Hernandez, C. Flores-Lopez, and M.A. Capo-Arteaga. 2000. Locations of endangered spruce populations in Mexico and the demography of Picea chihuahuana. Madroño 47(2):71-78.

Ledig, F.T., P.D. Hodgkiss, K.V. Krutovskii, D.B. Neale, and T. Eguiluz-Piedra. 2004. Relationships among the Spruces (Picea, Pinaceae) of Southwestern North America. Systematic Botany 29(2):275-295.

Taylor, R.J., and T.F. Patterson. 1980. Biosystematics of Mexican spruce species and populations. Taxon 29 (4): 421-469.

This page co-edited with Michael P. Frankis, 1998.12.

See also

Last Modified 2014-10-12