A review of dipterocarps - Center for International Forestry Research
A review of dipterocarps - Center for International Forestry Research
A review of dipterocarps - Center for International Forestry Research
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Biogeography and Evolutionary Systematics <strong>of</strong> Dipterocarpaceae<br />
section Shorea), Pentacme, Doona and Anthoshorea<br />
which <strong>for</strong>m a full complement <strong>of</strong> supraspecific taxa<br />
exclusively confined to canopy in the Asian seasonal<br />
tropics (Ashton 1979a). But many other emergent<br />
Shorea, especially the Richetioides group, have small<br />
flowers, whereas Vatica and Stemonoporus (many <strong>of</strong><br />
which flower beneath the canopy) have large flowers (as<br />
big as Parashorea or Anthoshorea).<br />
The anther and stamen sizes broadly follow the same<br />
trend: a) in the seasonal area the anthers are large,<br />
elongate and bright yellow <strong>for</strong> Vateria, Vateriopsis,<br />
Dipterocarpus, Parashorea, and Pentacme; and b) the<br />
same type <strong>of</strong> anthers also characterise certain taxa<br />
confined to aseasonal regions: Dryobalanops,<br />
Cotylelobium, Neobalanocarpus, Stemonoporus,<br />
Ashton’s Shorea section Rubellae, and Doona. In the<br />
other taxa, such as Anthoshorea and Ovalis, anthers are<br />
smaller, white and subglobose to ellipsoid; Richetioides<br />
presents the smaller ones. The African taxa seem to<br />
possess numerous stamens <strong>of</strong> medium size (drawings<br />
<strong>of</strong> Verdcourt 1989).<br />
The number <strong>of</strong> stamens (Ashton 1979a) is <strong>of</strong>ten 15:<br />
Vateria, Vateriopsis, most Dipterocarpus species,<br />
Anisoptera section Anisoptera, Dryobalanops, Shorea<br />
sections Shorea and Rubellae, 6 species <strong>of</strong> Anthoshorea<br />
all in seasonal sites, Ovalis, 1 species <strong>of</strong> Brachypterae,<br />
1 species <strong>of</strong> Richetioides, and 3 species <strong>of</strong> Hopea (2 <strong>of</strong><br />
which are in seasonal sites). Ten species have less than<br />
15 stamens: 10 stamens in 6 species <strong>of</strong> Hopea and 3<br />
species <strong>of</strong> Richetioides, 5 stamens in 2 species <strong>of</strong><br />
Stemonoporus and 1 species <strong>of</strong> Vatica.<br />
Large flowers produce large pollen grains (Muller<br />
1979). Flower and pollen dimensions will interfere with<br />
potential pollinators. Clear relations have been<br />
demonstrated between ovary shapes and sizes within<br />
Shorea sensu lato subgroups and pollinator size or<br />
taxonomical group (Chan and Appanah 1980, Appanah<br />
and Chan 1981, Appanah 1990). Bees pollinate large<br />
yellow elongate anthers while thrips pollinate small,<br />
white anthers. Bees prevail in seasonal tropics and Sri<br />
Lanka. Pollination changes during geological to present<br />
times probably explain much <strong>of</strong> the present aspect <strong>of</strong><br />
<strong>dipterocarps</strong>. This is an important point to consider when<br />
planting trees outside their original areas. Forest<br />
degradation may result in the absence <strong>of</strong> tree<br />
reproduction by extinction <strong>of</strong> pollinators.<br />
The biggest fruits are in taxa with large flowers, and<br />
more frequently in species producing wingless-fruits<br />
24<br />
than in species with winged fruits. There is also a relation<br />
between large dimensions and the development <strong>of</strong> a<br />
protective thickening <strong>of</strong> pericarp and/or calyx base to<br />
prevent dehydration <strong>of</strong> the embryo and sometimes<br />
permit floating <strong>of</strong> the fruit (Maury 1978, Maury-Lechon<br />
1979b, Maury-Lechon and Ponge 1979). Thickened sepal<br />
bases are a defining character <strong>of</strong> Shorea sensu Ashton,<br />
but do not occur in Anisoptera, Upuna, Cotylelobium<br />
or Sunaptea. Pericarp thickenings characterise<br />
particularly the Pachynocarpus and Vatica groups <strong>of</strong><br />
genus Vatica and genera Stemonoporus and Vateria. The<br />
thickening is <strong>of</strong> different type in Monotoideae and the<br />
case <strong>of</strong> Dipterocarpus remains apart because <strong>of</strong> the<br />
variously thickened calyx ornamentations (tubercules,<br />
simple or folded wings). The protective thickenings<br />
mainly develop in the group <strong>of</strong> taxa <strong>for</strong>ming 15 elongate,<br />
large, yellow anthers. Large fruits are produced in smaller<br />
numbers, and they represent an investment which lowers<br />
risks in weakly lit places. The increased size <strong>of</strong> seedembryo<br />
probably demonstrates a trial <strong>for</strong> better survival<br />
in unpredictable habitats with irregular supply <strong>of</strong> light<br />
and nutrients (and water) during the germination period<br />
<strong>of</strong> non-dormant seeds. However, fewer fruits are<br />
produced, so that investment is in fewer high-cost seeds<br />
bearing other risks <strong>of</strong> probably lower intensity. Animal<br />
predation is mainly by insects and seeds do germinate<br />
and develop normal seedlings in spite <strong>of</strong> insect larvae<br />
which continue their development within the fleshy<br />
cotyledonary limbs; human predation is more drastic and<br />
mainly corresponds to traditional and industrial oil<br />
extraction.<br />
The 5-winged fruits <strong>of</strong> Pakaraimaea, Monotes and<br />
Marquesia clearly disperse in open and windy habitats,<br />
as probably do that <strong>of</strong> Pseudomonotes (detailed<br />
in<strong>for</strong>mation not yet available). In these taxa pollen and<br />
nuts show evident adaptations to the dry conditions <strong>of</strong><br />
their seasonal climates: thick layers and protected<br />
apertures, while the thin coriaceous pericarp <strong>of</strong> the ripe<br />
fruit <strong>of</strong> Marquesia excelsa is an exception (Maury et<br />
al. 1975a, b, Maury 1978, Maury-Lechon 1979a, b,<br />
Maury-Lechon and Ponge 1979). In Asia the wingedlight<br />
fruits <strong>of</strong> Sunaptea and Cotylelobium, <strong>of</strong> certain<br />
species <strong>of</strong> Hopea, Shorea (Ashton sensu lato) and<br />
Upuna present thin pericarps, even in seasonal regions.<br />
Asian taxa have developed winged fruits in seasonal<br />
and aseasonal regions. In closed <strong>for</strong>ests these fruit wings<br />
have limited possibilities <strong>for</strong> dispersal. However, over<br />
the canopy and at <strong>for</strong>est borders, storms and very strong<br />
winds at the beginning <strong>of</strong> the rainy season may transport