A review of dipterocarps - Center for International Forestry Research

Biogeography and Evolutionary Systematics of Dipterocarpaceae
bricate) or 6, 8 or 10 (Valvate), cotyledonary vascular
bundles uni to trilacunar (Imbricate) or tri to
multilacunar (Valvate), stomatal types in first leaves
paracytic, or para-cyclocytic, or anomo-cyclocytic
(Imbricate) versus cyclocytic or anomocytic or
anisocytic (Valvate), stomata elongate and sunken
in the epiderm (Imbricate) or round and raised
above the epiderm (Valvate).
The overall pattern of infrageneric variation supports
the establishment of the two Asian groups Dipterocarpi
and Shoreae (tribes: Ashton 1979b) or Valvate and
Imbricate (Maury 1979a). Wood anatomy
(Parameswaran and Gottwald 1979), palynology and
characters of fruit-embryo-seedling (Maury et al. 1975a,
b, Maury 1978, Maury-Lechon 1979a, b, Maury-Lechon
and Ponge 1979) locate the genus Dryobalanops at an
intermediary position between Shoreae-Imbricate and
Dipterocarpi-Valvate groups. Its calyx in ripe fruit is
subvalvate, thus close to the Valvate group, but the
chromosome number is 7 as in the Imbricate group.
The basic distinctions of these two groups are:
1. Valvate- Dipterocarpi group: base of sepals in calyx
of ripe fruit valvate, vessels solitary, resin canals scattered;
basic chromosome number n=11: Vateria,
Vateriopsis, Stemonoporus, Vatica, Cotylelobium,
Upuna, Anisoptera, Dipterocarpus. and
2. Imbricate-Shoreae group: fruit sepals imbricate at
the incrassate-cupped base of the ripe fruit, vessels
always grouped, resin canals in tangential bands, basic
number n=7; Shorea, Parashorea, Hopea,
Neobalanocarpus.
Loosely associated genera such as Vateria L. and
Vateriopsis Heim are distinguishable on many characters
such as floral parts, bark, fruit, embryo, germination, and
wood anatomy, as are Stemonoporus Thw., Cotylelobium
Pierre and Sunaptea Griff. by the same features. The
other taxa in Vatica L. show the same nervation type and
rather comparable adult wood or bark anatomy. However,
a high diversity occurs in vascular structures in the
seedling cotyledonary-node (Maury 1978; Fig. 677-679,
p. 309-313, Maury-Lechon 1979a, b; Fig. 16 p. 100). A
certain diversity also exists in flower-bud development
(Maury 1978; vol. II tables VI, VII, p. 51-52) or stylestigma
and stamen shapes (Woon and Keng 1979; Fig.
30, p. 40). A high diversity is observed in fruit forms of
sepal aestivation and wing-accrescence, and pericarp or
sepal incrassatescence (Symington 1943, Ashton 1964;
Fig. 10, 1968; Fig. 29, Maury 1978; Vol. II, Tables VI,
28
VII, p. 51-52). Stemonoporus present a unique terminal
bud set in a depression at the twig apex which is prolonged
beyond the last leaf insertion. In Anisoptera the two
sections are based on floral and bark aspects. Parashorea
stands out on account of its flower and its 5 or non-winged
fruit.
The infrageneric classification of the three genera
Shorea, Hopea and Neobalanocarpus is more complex.
Shorea and Hopea differ morphologically by the number
of thickened bases of calyx (respectively 3 and 2) which
eventually expand into wings; this is the sole consistent
difference. Shoreas are mainly tall emergent or canopy
trees while Hopeas mainly remain understorey or in the
canopy. Flowers and leaf venation may distinguish the
two genera but these characters also separate the sections
within the two genera and are not constant for either genus
as a whole (Ashton 1979b). Hopea sections differ by
leaf characters only, while within each section the two
subsections are principally classified by the shape of the
floral ovary.
Heim (1892) first and Symington (1943) afterwards
produced sound groupings of Shorea and later noticed
that floral characters closely correlate with field
characters of bark morphology and wood anatomy in
defining groups. However, Symington never gave a formal
nomenclature to his groups (Ashton 1979b). Floral
characters also correlate with pollination biology (Chan
1977, 1981, Chan and Appanah 1980, Appanah and Chan
1981, Appanah 1990). For these reasons and in light of
the Woon and Keng’s (1979) results, additional emphasis
has to be put on the importance of stamen shapes in the
family Dipterocarpaceae.
Some of the characters by which the groups in
Shorea are recognised are also those which distinguish
Cotylelobium, Vatica, Stemonoporus, Vateria and
Vateriopsis as genera. This evidence was stressed by
Parameswaran and Gottwald (1979) from wood anatomy
studies. They stated that groups Anthoshorea, Shorea,
Richetia, and Mutica merited generic status. However,
Ashton maintains a different status for these groupings
in Shorea. On the contrary he gives generic rank to Vatica
and its allies. He justifies this difference of treatment
owing to the presence of species with intermediate
character states between most of the flowers within the
Shorea group, as opposed to their absence between the
taxa of the Vatica group. This situation could result from
different degrees of diversification potential, and merits
further investigation.