Pinus leiophylla var. chihuahuana (Engelm.) Shaw

  • Authority

    Farjon, Aljos K. & Styles, Brian T. 1997. Pinus (Pinaceae). Fl. Neotrop. Monogr. 75: 1-291. (Published by NYBG Press)

  • Family

    Pinaceae

  • Scientific Name

    Pinus leiophylla var. chihuahuana (Engelm.) Shaw

  • Type

    Type. Mexico. Chihuahua: Cosiquiriachi, Oct 1846, Wislizenus 232 (holotype, MO 1817023, and cone MO 1635446).

  • Synonyms

    Pinus chihuahuana Engelm.

  • Description

    Variety Description - Tree, medium size, height to 15-25 m, often not more than 10 m, dbh to 20-60 cm. Trunk monopodial, erect, often forked higher up. Shoots reddish brown, often glaucous. Leaves in fascicles of (2-) 3(-4, rarely 5), (4-)6-12(-l4) cm X 0.9-1.3(-1.5) mm. Stomata in (4-)5-8(-9) lines on the convex abaxial face, in 3-4 lines on each adaxial face. Resin ducts in the leaves (3-)4-6(-7), medial, occasionally 1-2 internal.

  • Discussion

    Uses. Along with many other species of pine in the Sierra Madre Occidental, Pinus leiophylla has been heavily exploited for timber in the latter half of this century. Because of its high resin content, it does not provide high-quality wood but at the same time is a producer of good resin, for which it is tapped. The variety chihuahuana, an equally prolific producer of resin, is less exploited for timber.

    Under Coniferae, Schlechtendal and Chamisso (1831) described two new species of Pinus, P. patula and P. leiophylla, based on Schiede (& Deppe) 1108 and 1109 respectively, and both from (approximately) the same locality. Schiede (& Deppe) 1109 consists of a single sheet with two sterile branchlets at HAL, which is the holotype of P. leiophylla. Deppe, mentioned as the second collector in the protologue, does not appear on the labels. Another collection in HAL, Schiede 1117, bears a small cone, but in the protologue it is claimed no cones were observed (“nobis deficiente”). Although meagre, Schiede 1109 is unambiguous and need not be supplemented with Schiede 1117 as an epitype; but as another specimen annotated by Schlechtendal, the latter helps to interpret his taxon more fully. Lambert (1832, t. 21) had the species drawn for his third edition from a specimen with a cone received from the collector(s).

    Shaw (1904a) was the first author to describe the prolonged growth of the ovuliferous cone, a feature shared by P. pinea of the Mediterranean but unique in Latin American pines. It shares this feature with its variety, P. leiophylla var. chihuahuana. Similarly, the ability to coppice, shared by P rigida of the eastern United States, is an uncommon phenomenon present in both varieties. A related feature are adventitious (“epicormic”) shoots along the trunk of mature trees.

    Carvajal (1986) described Pinus lumholtzii var. microphylla based on Carvajal 4031 (CREG!) but also referring to material collected tentatively as P. chihuahuana. His conclusion, that it resembles P. lumholtzii more, appears to have been withdrawn in Carvajal & McVaugh, 1992: 71, where its type is synonymized with P leiophylla var. leiophylla. Pinus lumholtzii has sometimes short, non-pendulous leaves and can in those cases become confused with P. leiophylla var. chihuahuana (Martínez, 1948; see also the treatment of P. lumholtzii, this volume).

    The numerous “species” described or named by Roezl, most of which were synonymized by Parlatore (1868), have been typified for the first time from Roezl's material in Fl and R A general comment on Roezl and his pines is given under the treatment of Pinus montezumae.

    In the Botanical Appendix to Wislizenus (1848), Engelmann described three new species of pines “entirely different from those found farther north, but perhaps identical with some species from the Pacific coast.” One of them is Pinus chihuahuana. No comparisons were made with other pines already described from the Sierra Madre Occidental and occurring farther south. In his revision of the genus, Engelmann (1880a) classified P. leiophylla in a different subgroup from P. chihuahuana, although he observed its deciduous fascicle sheaths. [Hartweg 441 does indeed have persistent sheaths, but it belongs to P. teocote, not to P. leiophylla, where Engelmann (1880a) and Parlatore (1868) cited it]. Not until Shaw (1904b, 1909) recognized the prolonged phenology as well as the shared character of adventitious shoots and coppicing capacity were P. leiophylla and P. chihuahuana correctly interpreted as conspecific.

    Engelmann (in Wislizenus, 1848) did not indicate which of the collections of Wislizenus pertains to his new species, and neither does Parlatore (1868), who received some material on loan from Engelmann (see Carvajal & McVaugh, 1992: 69), as is annotated by Engelmann on the sheet of Wislizenus 232 (MO 1817023). This sheet and a cone (MO 1635446), returned from the loan to Parlatore, are to be considered the holotype of P. chihuahuana.

    Martínez (1948), who maintained both taxa at the rank of species, nevertheless admitted that P. chihuahuana in the southern part of its range merges with P. leiophylla to such an extent that it becomes very difficult to distinguish them. We, too, have found this to be the case; and since there seem to be no other than quantitative foliar characters to differentiate them, while they share two very distinct and unique qualitative features, these combined arguments strongly support treatment at varietal rank. On the other hand, in certain areas in Durango the two taxa retain their differences over large areas, where typical P. leiophylla with fascicles of five, slender, pendulous leaves grow in proximity to “pure” P. leiophylla var. chihuahuana with fascicles of three, thick, spreading leaves (Styles, 1992). Further assessment of the relationship of these two pines and their putative relatives, including molecular genetics, is desirable.

    Distribution and Ecology: United States: SE Arizona, SW New Mexico. Mexico. Along the Sierra Madre Occidental in NE Sonora, W Chihuahua, Durango, Nayarit, N Jalisco, and Zacatecas. Pinus leiophylla var. chihuahuana was included with the species in the distribution map given by Critchfield and Little (1966); it has been recognized as a distinct species by Perry (1991), who gives a generalized map roughly in accordance with our findings. Although largely sympatric, the altitudinal range of var. chihuahuana is narrower—1500-2700(-2950) m but this is in part due to the fact that it does not occur on some of the high volcanos of central Mexico. In the Sierra Madre Occidental its lower limit usually is below the level of var. leiophylla. Here it may be found in semi-arid habitat with P. cembroides, Juniperus spp., and Xerophytes like Opuntia and Arctostaphylos. Higher up, its habitat is similar to that described above. Its poor growth in some areas is related to lower precipitation and rocky, poor, shallow soils, especially at lower and middle altitudes.

    Phenology: The time of pollen dispersal is not recorded.

  • Distribution

    Mexico North America| Chihuahua Mexico North America| Durango Mexico North America| Nayarit Mexico North America| Sonora Mexico North America| Zacatecas Mexico North America|