Syn.: Pinus pseudostrobus Lindl. subsp. yecorensis (Debreczy et I. Rácz) Silba 2009. Type collection southeast Sonora near Yecora, 1800 m, 1994.05.09; Debreczy, Rácz, Biró, et al. 39798 (holotype BP, isotypes A, CHAP, E, MEXU, NA).
There is some doubt about the validity of this taxon. Farjon and Styles (1997) placed it into synonymy with Pinus pseudostrobus var. pseudostrobus and its morphological characters appear to fall fully within the range of variability in that taxon. However, its occurence is more northerly than that of P. pseudostrobus and its ecological setting, in woodlands below the elevation of continuous forest, is somewhat distinct. Moreover, a molecular analysis by Gernandt et al. (2009) placed it in a clade with P. douglasiana and P. maximinoi, consistent with the analysis of Felger et al. (2001) who allied it with P. douglasiana on purely morphological grounds. It may prove to be more accurately described as a variety of P. douglasiana but has not yet been named as such.
There is one described variety, P. yecorensis Debreczy et A. Racz var. sinaloensis Debreczy et I. Rácz 1995.
Trees to 30 m tall and 95 cm dbh, at maturity with a spreading, dome-shaped crown. Bark red-brown, rough, with dark longitudinal furrows. Twigs >10 mm thick, scaly, initially glaucous. Leaves (4-)5(-6) per fascicle, ca. 1 mm thick and 20-35(-38) cm long, slightly drooping. Fascicle sheaths dark, persistent. Seed cones pendent, subsessile or on a thick peduncle up to 15 mm long, woody, 5-15.5 cm long, symmetric to slightly asymmetrical, somewhat or variably persistent, peduncle falling with the cone or sometimes not, remaining on the tree with a few basal scales. Cone scales stout, apophysis moderately to very thickened, umbo dorsal (downward-pointing) with a small prickle. Seeds ovoid, 6.0-8.4 mm long with a broad 16-25 mm wing. Pollen shed March-April (Felger et al. 2001).
Compared to P. engelmannii, P. yecorensis has a denser crown, usually more slender twigs, and brighter green, thinner leaves with five (not 3) leaves per fascicle. Compared to P. arizonica, it has darker, rough bark; thicker twigs; longer, more drooping leaves; larger, heavier cones; thicker cone scale tips; and blunt prickles. Compared to P. oocarpa, it has longer and slightly thinner, more drooping leaves; larger seed cones; and scales with thicker tips and lacks evidence of a conspicuous black band on the inner surface (Felger et al. 2001).
Mexico: Sonora, Chihuahua, Sinaloa, Durango; on the Pacific slopes of the Sierra Madre Occidental at 900-1975 m elevation, mainly in woodlands with Quercus spp. and Pinus spp., including P. oocarpa, P. leiophylla var. chihuahuana and P. engelmannii; often it is lower than any other pines. In one area it grows at elevations as low as 900 m on hydrothermal soils in a landscape otherwise dominated by tropical deciduous forest; otherwise it has not been recorded below 1200 m elevation (Felger et al. 2001).
No records known (as of 2012.11).
No records known (as of 2012.11).
No use recorded (as of 2012.11).
Exploited for lumber (Felger et al. 2001).
See the distribution map.
The epithet yecorensis comes from the town of Yecora in Sonora, near which the species was discovered.
Debreczy, Z. and I. Rácz. 1995. New species and varieties of conifers from Mexico. Phytologia 78(4):217. Available at the Biodiversity Heritage Library, accessed 2012.11.22.
Felger, R.S., M.B. Johnson, and M.F. Wilson. 2001. The trees of Sonora, Mexico. Oxford: Oxford University Press. ISBN 0-19-512891-5.
Gernandt, D.S., S. Hernández-León, E. Salgado-Hernández, and J.A. Pérez de la Rosa. 2009. Phylogenetic relationships of Pinus subsection Ponderosae inferred from rapidly evolving cpDNA regions. Systematic Botany 34:481-491.
Last Modified 2017-12-29