Pinus pinceana Gordon

  • 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 pinceana Gordon

  • Type

    Type. Mexico. Morelos?: Location from protologue:  upon a mountain along the road to the city of Mexico, at a place called Guernavaca [Cuernavaca], . . . alt. 8000-9000 ft.," Ehrenberg s.n. (holotype, not found; isotype, W).

  • Synonyms

    Pinus latisquama Engelm.

  • Description

    Species Description - Tree, small and bushy, or a large shrub, height to 6-10(-12) m, dbh to 20-30 cm. Trunk short, often branching from near the ground, erect, monopodial, contorted or forked. Bark thin, smooth, only on the lower part of the trunk and lowest branches exfoliating into irregular plates, eventually longitudinally fissured on old trees, with occasional horizontal cracks, on young trees and branches thin, smooth, brownish grey, weathering grey. Branches of first order long, thick, contorted, ascending or spreading, of higher orders long, slender, flexible, the ultimate branches drooping to pendulous, forming a broad, irregular, open crown with branches of young trees often drooping to the ground. Shoots long, slender, flexible, smooth, with small, non-decurrent, widely spaced pulvini, brownish grey to grey. Cataphylls small, 3-4 mm long, ligulate to narrowly triangular, with erose-hyaline margins, light brown, soon deciduous. Vegetative buds small, inconspicuous, ovoid-globose to ovoid-conical, the terminal bud 4-6 mm long, the laterals smaller, not resinous; the scales imbricate, appressed, narrowly triangular, light brown. Fascicle sheaths ca. 10 mm long; the scales initially imbricate, ligulate-linear, soon spreading or curling and deciduous, only the basal part may remain for some time in some fascicles. Leaves in fascicles of 3, rarely 4, in sparse tufts toward the ends of drooping or pendulous branchlets, remote, spreading at 30-60° from the shoot, persisting 2-3 years, straight, rigid, 5-l2(-l4) cm (often variable on a single shoot) X 0.8-1.2 mm, with entire margins, acute, greyish green. Stomata: Most leaves epistomatic, with 2-4(-5) lines on each adaxial face, some leaves amphistomatic with in addition 2 faint, intermittent lines of stomata on the abaxial face. Leaf anatomy: Triangular to transverse-triangular in cross section, with a convex abaxial side; epidermis thick: hypodermis with 1-2 layers of cells; resin ducts 2, external, toward the margins on the abaxial side: stele terete; cells of endodermis large, with thin walls; vascular bundle single. Pollen cones crowded or more remote on the proximal part of a new shoot, subtended by broad, chartaceous, yellowish bracts, ovoid-oblong, 8-10 X 4-5 mm, purplish or yellow-ish. Microsporophyll subpeltate, broadening from a cuneate base to a broadly obovate, cuspidate distal part. Seed cones lateral, not on ultimate branches, solitary or rarely in pairs on slender, curved and easily breaking peduncles, spreading, mature cones pendent through the habit of the branchlets. Immature cones ovoid-oblong, obtuse, purplish, maturing in two years. Mature cones ovoid-oblong to short cylindrical, often irregular, 5-10 X 3.5-6(-7) cm when open. Seed scales ca. 60-80, parting only slightly or sometimes more widely, weakly attached to the slender cone rachis with a small cuneate base, therefore easily moveable, thick woody, concavo-convex, with (l-)2 deep, cup-like depressions holding the seeds, puberulent in fresh cones, reddish brown abaxially, dark brown adaxially. Apophysis irregular, prominently raised, transversely keeled, rhombic to pentagonal in outline, the upper margin angular or undulating, lustrous red-brown, sometimes with concentric colour rings or radially striated. Umbo dorsal, flattened at apex, transversely rhombic or oval in outline, up to 10 mm wide, 5 mm high, grey, with a minute prickle. Seeds (I-)2 per scale (1 often abortive), obovoid, obtuse-angular, 11-14 X 7-8 mm, wingless when detached from the scale, brown, with a darker side where the seed was adnate to the scale depression. Integument ca. 1 mm thick, hard. Seed wings absent from detached seeds, sometimes rudimental tissue on the scale around the seed depression. Seedlings (number of cotyledons not observed) with chalk-white stems and narrowly linear, glaucous leaves appearing for 5-8 years.

  • Discussion

    Uses. This species is not commercially used; the seeds are edible (“piñones”) but trees are scarce, inaccessible, and far apart and usually with a low crop of cones compared to P. cembroides and its close relatives.

    When Gordon and Glendinning (Gordon, 1858) described Pinus pinceana, it was said to have been discovered by “M. Gheisbreght” [A. B. Ghiesbreght] in 1844 near Mextitlán in Hidalgo (20°36'N, 98°45'W) and collected under his “No. 34.” In P there is a collection Ghiesbreght 54 from 1842— 1843 made at that locality; an unnumbered specimen collected by the same author is in K, which is probably a duplicate. The description is instead based on a collection made by C. Ehrenberg and said to be from “upon a mountain along the road to the city of Mexico, at a place called Guemavaca, at an elevation of from 8000 to 9000 feet.” The city of Cuernavaca is in Morelos, but as later authors (Shaw, 1905a; Martínez, 1948) have pointed out, the species does not occur in that state and it was concluded by Mirov (1952) to be most likely an error on either Gordon’s or Ehrenberg's part. The type specimen, according to Shaw (1905a), is a single cone at K. No material collected by Ehrenberg, or obtained from Gordon’s herbarium, has been found there, but a fragmented cone "from Ch. Ehrenberg" is at W, sent to Endlicher by Lindley (through the Horticultural Society of London); Gordon may well have seen this cone. As there may still be some original material in other European herbaria, this specimen is here recognized as an isotype. It is perhaps due to some lack of memory by Ehrenberg that Gordon and Glendinning described this species as a tree growing 60 ft (20 m) high, but if they really had seen sufficient specimens of the foliage it is rather strange that they described the leaves to be “in threes, but frequently in two’s." Old fascicles may loose a leaf sometimes before they fall entirely, but on normal fascicles they would be in threes, rarely fours. Clearly, Gordon and his associate were not at all familiar with this species but, following the craze of the day (Roezl, 1858), were eager to describe “novelties for the garden” at the slightest opportunity. It is a remarkable stroke of luck that they hit upon a unique species.

    Engelmann (1882) based his Pinus latisquama on a later collection (Palmer 1299, MO), but as Shaw (1905a) had already observed, this material from near Saltillo in Coahuila became mixed on the same sheet with a branch of what A. Farjon identified as P flexilis James, probably from the United States. For this reason, Engelmann, who was not aware of this mixture, described his species with short (3.5-5 cm), extremely slender, slightly serrulate leaves in fascicles of 5 and with a cone identical to Gordon’s species. On the type sheet 1 of 2 is a very small branchlet with ca. 5 cm long leaves in fascicles of 3, but apparently this escaped Engelmann’s attention. All that is now left of the cone of Palmer 1299 is a seed scale (sheet 2 of 2), but, in conjunction with an illustration of a cone on the same sheet, it suffices to identify Engelmann’s species unambiguously.

    The morphological, chemical, and molecular characters of Pinus pinceana place it closer to P. maximartinezii (Malusa, 1992; Zavarin & Snajberk, 1987; Pérez de la Rosa et al., 1995) than to P. cembroides and its closely related taxa (e.g., P. edulis, P. remota, P. quadrifolia). There is rather convincing morphological evidence that these two species are also more closely related to P. bungeana and P. gerardiana of E Asia than to the P. cembroides “complex” of SW North America (Farjon, 1984; Bailey & Hawksworth, 1988; Malusa, 1992). This could mean, that they are to be seen as palaeo-relicts, as opposed to the pinyon pines sensu stricto, which appear to have undergone allopatric or parapatric speciation in relation to Tertiary climatic change in the region (Malusa, 1992).

    Distribution and Ecology: Mexico: Scattered in Coahuila, N Zacatecas, San Luis Potosi, Queretaro, and Hidalgo. The locality (along the road to Mexico City at Cuernavaca) stated in the protologue is probably an error. It occurs often on calcareous slopes and in ravines (barrancas) at 14002300 m in arid and semi-arid mountains of NE Mexico. Annual precipitation is lower than in the pinyon-juniper belt (ca. 300-400 mm, according to Perry, 1991) and is concentrated in the summer. This species sometimes occurs with Pinus cembroides, more often with Juniperus flaccida, and usually with numerous sclerophyllous or deciduous shrubs—e.g., Prosopis (in arroyos), Mimosa, Karwinskia, Leucaena, Sophora, Quercus, Cercocarpus, Gochnatia, Fouquieria—as well as Yucca, Agave, Opuntia. The trees are often widely scattered in this vegetation. Phenology: Pollen dispersal has been observed in Apri 1-May.

  • Distribution

    Mexico North America| Coahuila Mexico North America| Hidalgo Mexico North America| Querétaro Mexico North America| San Luis Potosí Mexico North America| Zacatecas Mexico North America|