A review of dipterocarps - Center for International Forestry Research

Biogeography and Evolutionary Systematics of Dipterocarpaceae
vernation, oblong-ovate and chartaceous, with a vestigial
gland on the midrib at the base of the blade, triangular,
glabrous and caducous stipules. Inflorescences are
axillary, subcymose, with bisexual 5-merous flowers,
showing a glabrous calyx with 5 lobes which form a
shallow cup at the base, a glabrous corolla with contorted
petals, the petals longer than sepals, the stamens
numerous, cyclic, hypogynous, the anthers basi-versatile,
the connective broad and very expanded, continued into
a triangular appendage one-fourth to one-half as long as
the body of the anther, the pollen grains tricolporate,
rarely tetracolporate, sometimes trisyncolpate, exine
minutely reticulate to foveolate, columellate,
tectateperforate, the ovary glabrous, 3-locular, one ovule
per loculus. The fruit is a dry nut, glabrous with a woody
pericarp, a persistent calyx with 5-winged accrescent
sepals, thinly papyraceous, and 1 seed per fruit. As in
African monotoids the wood anatomy of
Pseudomonotes shows solitary vessels (occasionally in
radial pairs), rays mainly uniseriate with infrequent
biseriate portions, heterocellular rays, resinous contents
present in vessel, rays and parenchyma cells, and presence
of secretory cavities in the pith. No economic use is
known but the local name (Nonuya Indians) means (in
Spanish) ‘arbol de madera astillosa’, thus wood is
probably used by native people.
Pseudomonotes, Monotes and Marquesia may share
solitary vessels or vessels in radial pairs, simple
perforation plates, resinous content present in the
vessels, rays and parenchyma cells, wood rays, presence
of secretory cavities in the pith, lack of resin canals,
single gland on the upper surface of the lamina at the
base of the midrib, basi-versatile anthers and tricolporate
pollen grains. Pseudomonotes differs from the Asian
dipterocarps in the absence of fasciculate trichomes,
multiserate rays, wood, ovary and leaves resin canals and
tricolpate grains, and having one ovule per locule with
nearly basal placentation.
Dipterocarpoideae, the Asian dipterocarps are small
or large, resinous, usually evergreen trees, often
buttressed and usually developing scaly or fissured bark
on large trees. Some or most parts present a tomentum,
with alternate simple leaves, margin entire or sinuate,
not crenate, penninerved, with a more or less geniculate
petiole, stipules paired, large or small, persistent or
fugaceous and leaving small to amplexical scars,
inflorescence in panicles with racemose branches usually
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with flowers secund, i.e. turned to one side, except in
Upuna (cymose appearance perhaps due to reduction of
a panicle of the Shorea type, and an even stronger
reduction in some Stemonoporus and Dipterocarpus
rotundifolius, whose flowers are solitary; in Kostermans
1985). Extra-floral nectaries were recently found in
many genera (Ashton, personal communication). In the
5-merous flower, petals are longer than sepals and
variously pubescent, calyx persistent with 0, 2, 3 or 5
sepals enlarged into wing-like lobes in fruit, either free
down to the base, forming a cup or a tube more or less
enclosing the fruit, adnate to or free from it; when free
to the base they are mostly imbricate. The basifixed erect
anthers bear mainly 2 pollen sacs (rarely 4) on the
connective terminated by a short or prominent
appendage. Pollen grains are tricolpate with a 2 or 3layered
exine. The ovary is superior or semi-inferior, 3
(rarely 2) locular, each loculus contains 2 ovules. The
fruit is loculicidally indehiscent, or at length splitting
irregularly, or opening at staminal pore at germination,
normally 1-seeded (sometimes 2, exceptionally up to
12 or 18), with woody pericarp and persistent more or
less aliform sepals. The stipules are often conspicuously
large. Wood, ovary and leaves contain resin secretory
canals. Wood rays are multiseriate (Maguire et al.
1977).
Ecology
Monotes grows in deciduous formations, and most
Marquesia species form dry deciduous forests or
savanna woodlands. One species, M. excelsa, grows in
Gabonese rain forest and resembles the Malaysian rain
forest dipterocarps. Pseudomonotes is found in wet,
evergreen rain forest and Pakaraimaea in evergreen
associations.
Pakaraimaea dipterocarpacea may dominate in dry
seasonal evergreen forests on a variety of topographical
situations, at altitudes of 450 to 600 m, on weakly
ferralitic sandstones. The tallest tree recorded is 20 m
with a diameter of 50 cm. Older or damaged trees freely
coppice from the base as do some savanna dipterocarps
in Asian seasonal regions.
Pseudomonotes tropenbosii develops at 200-300 m,
on clayey to sandy sediments, on summits of hills and
along shoulders of slopes. These trees constitute the
most ecologically important species in the rain forest a
few kilometres south of Araracuara (Colombia).