Pinus elliottii var. densa Little & K.W.Dorman

  • 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 elliottii var. densa Little & K.W.Dorman

  • Type

    Type. United States. Florida: Hendry Co., SE of La Belle, 19 Jan 1951, Little & Dorman 14033 (holotype, US; isotypes, F, NY).

  • Synonyms

    Pinus elliottii var. densa Little & K.W.Dorman, Pinus densa (Little & K.W.Dorman) Silba, Pinus densa var. austrokeysensis Silba, Pinus caribaea Morelet, Pinus heterophylla (Elliott) Sudw.

  • Description

    Variety Description - Tree, small to medium or occasionally tall, rapidly growing at early age (ca. 20 years), height to 15-25(-30) m, dbh to 50-100 cm. Trunk monopodial, erect, straight or somewhat tortuous. Bark thick, scaly, breaking into large, irregular plates, divided by deep fissures, reddish brown, weathering grey; on young trees rough, scaly, reddish brown. Branches of first order few, long, spreading or ascending, tortuous in older trees; of higher orders spreading or ascending, the ultimate branches assurging, forming an open, rounded or flat-topped crown. Shoots often multinodal, on lateral shoots uninodal, thick, rigid, orange-brown to brown, with small, decurrent, caducous pulvini. Cataphylls small, subulate, scarious, recurved, brown, with hyaline-erose margins, early deciduous. Vegetative buds ovoid-conical, the terminal buds 15-25 mm long, the laterals smaller, not resinous; the scales imbricate, linear-acuminate, reddish brown with white, ciliate margins. Fascicle sheaths initially 10-15 mm long, persistent but slightly reduced to ca. 8 mm in mature foliage; scales reddish brown with white, ciliate margins, weathering grey. Leaves in fascicles of 2(-3), in dense tufts near the ends of branches, spreading obliquely, rigid, straight or slightly twisted, (16-)18-25(-30) cm X ca. 1.5 mm, margins serrulate, apex acute-acuminate, pungent, dark green, slightly lustrous. Stomata on all faces of leaves, in 10-12 lines on the convex abaxial face and ca. 10 lines on the adaxial face. Leaf anatomy: Cross section semicircular, with three leaves in a fascicle transverse-triangular; hypodermis with (2-)3-4(-5) layers of cells; resin ducts 3-9(-11), internal, sometimes 1-2(-4) medial, variable in diam.; stele elliptic in cross section, outer cell walls of endodermis not thickened; vascular bundles 2, distinctly separate, sometimes connate. Pollen cones crowded near the proximal end of a new shoot in short clusters, subtended by triangular, reddish brown bracts, ovoid-oblong, then cylindrical, 30-50 X 5-8 mm, at first purplish, then reddish brown; microsporophylls peltate, the distal part radially striate, with erose-denticulate margins. Seed cones subterminal, commonly in whorls of 25 or more, sometimes 2(-3) whorls on multinodal shoots, on 10-20 mm long, stout, scaly peduncles, erect at pollination but soon spreading or recurved, deciduous. Immature cones ovoid to ellipsoidal, 1113 X 6 mm, pinkish to pale purple, with greenish apophyses, maturing time two seasons. Mature cones ovoid-attenuate to ovoid-conical when closed, ovoid to broad cylindrical when opened, symmetrical, (5-)7-12(-15) X (4-)6-8.5 cm when open. Seed scales ca. 120-150, readily parting except near the base, thin woody, flat, oblong, straight or slightly recurved, nearly symmetrical, dark brown on the abaxial side, with lighter coloured marks of seed wings on the adaxial side. Apophysis transversely rhombic and keeled, more or less flattened or slightly raised, ochraceous to (reddish) brown, lustrous. Umbo dorsal, raised, with a persistent, stout, curved 1-2 mm long prickle, darker than the apophysis. Seeds obliquely ovoid, acute at proximal apex, or angular, 6-7 X 4 mm, mottled grey to nearly black. Seed wings articulate but effective, held to the seed by two claws, oblong or obliquely obovate, size variable with cone(scales): 15-30-(35) X up to 10 mm, light brown usually with darker tinge. Seedlings with a very thick hypocotyl, cotyledons 5-8; developing into a "grass stage" with delayed shoot elongation, a short stem near the ground, a thick taproot and mature foliage.

  • Discussion

    Uses. Pinus elliottii var. densa, the South Florida slash pine, is a regionally important timber tree prized for its dense wood. Substantial areas are logged regularly, but in most cases regeneration is rapid and successful. Substantial virgin stands (naturally subject to cyclic fires) are protected in Everglades National Park; on the other hand suburbanisation around Miami has been a factor in its decline there.

    For a considerable time botanists and foresters have applied the binomial Pinus caribaea to the slash pine (P. elliottii) of the SE United States, and particularly to the species in southern Florida, as well as to pines growing on the islands in the Caribbean and in Mesoamerica. However, Engelmann (1880a) already had renamed, fully described, and (beautifully) illustrated P. taeda L. var. heterophylla Elliott as P. elliottii, realizing that he could not use the epithet heterophylla at species rank. The lectotype of P. elliottii: United States, South Carolina, 20 Mar 1873, Mellichamp s.n. (MO no. 3941460) was designated by Farjon (1993). Sudworth’s (1893) raising of Elliott’s varietal epithet to species rank was both superfluous when published and illegitimate, as it created a later homonym.

    Little and Dorman (1952) restricted the concept of P. caribaea to Caribbean and Mesoamerican pines, recognizing a single variable taxon ranging from the Bahamas to Honduras, and further recognized P. elliottii with two varieties in the United States. Consequently, they named the southern Florida taxon Pinus elliottii var. densa. The botanical differences with P. elliottii var. elliottii include a prolonged, well-defined “grass stage” of the seedling which results from apical growth inhibition of the stem. This is apparently an inherited trait (Little & Dorman, 1954) as it is retained in seedling experiments outside natural conditions. Initial growth is invested in a thick hypocotyl; subsequently a large taproot is formed and the hypocotyl grows to a short “stem” up to 3 cm thick and 4 cm long (Fig. 2IB). Other differences appear to be more clinal (Price, 1989), such as the fewer leaves per fascicle and the thicker hypodermis in the leaves of var. densa.

    Gaussen (I960) raised the variety to specific rank, as he considered the characteristics of the seedling “evolutionarily important,” but by failing to cite the basionym he enabled Silba (1984) to publish the combination validly under the Code. A specimen with small cones and relatively long (ca. 30 cm) leaves, preserved in NY (for the cone, see Fig. 21F), was described by Silba (1990) as a distinct variety occurring in the Florida Keys. There is no such distinction occurring as fixed characters in the Florida Keys, as other collections from there amply testify.

    Distribution and Ecology: United States: In S Florida and north along the coasts to central Florida; also on eight of the Lower Florida Keys. Forming pure fire-climax forest or scattered in grassland on sandy lowland plains or on calcareous rock SW of Miami and in the Florida Keys. There is often a dense undergrowth of the palm Sabal palmetto and it can grow mixed with taller palms locally. Its altitudinal range is 1-20 m. The climate is subtropical to tropical on the Lower Florida Keys; annual precipitation is 100-150 mm, with a six-month dry winter period. It is especially well-adapted to frequent ground fires due to its “grass stage” strategy, which is found in the seedlings up to sapling age (Little & Dorman, 1954).

    Phenology: Pollen dispersal takes place from late February through March, depending on weather conditions (Little & Dorman, 1954).

  • Distribution

    United States of America North America| Florida United States of America North America|