A review of dipterocarps - Center for International Forestry Research

Biogeography and Evolutionary Systematics of Dipterocarpaceae
perhaps allow rapid spread of favourable ecotypes in
heterogeneous terrain. However apomixis should
probably lead to lowered genetic variability within
populations, and thus could still result in increased
probability of extinction when unadapted to the
environmental changes. Constant differences in habit,
morphology and reproductive biology exist between
emergent and understorey trees (Richards 1952, Hallé
et al. 1978, Yap 1982 in Ashton 1984). Ontogenesis thus
follows predictable patterns in the larger trees and
selection acts on these characteristics, which include tree
habit and leaf shape, irrespective of their systematic
relationships. These species present an ecological
complementarity. It is however, not certain that species
sharing a common habitat and geography will identically
respond from flower-bud initiation to sensitivity to light,
mycorrhizal invasion, water stress, seed predation, or
share the same pollinators and seed vectors (M.S. Ashton
1992, 1995). Ecological criteria such as seed water
content and seed resistance to desiccation are
expressions of the species’ biological plasticity and the
possible complementarity between species (Maury-
Lechon 1993). Certain species are abundant and others
rare. Detailed systematic and biosystematic comparisons
between rare and abundant congeners should bring some
answers (Ashton 1992). We need to confirm whether
the means exist for gene flow, and then to directly
measure the level and pattern of genetic variability.
Amenable source of evidence could also be tested for
the presence or absence of associations between
population distributions in space, and demographic and
population genetic studies are also required on the basis
of repeated observations. These observations and the use
of species’ complementarity would reinforce the
understanding of systematics and help the forest
managers to make decisions in rehabilitation and
conservation programmes (Maury-Lechon 1991, 1993,
1996).
Bearing in mind the economic value and the present
status of Dipterocarpaceae, it is also urgent to relate
phylogeny to comparative ecology within genera and
sections by a combination of:
1. molecular phylogenic studies, concentrating on genera
and below;
2. comparative demographic studies of groups of related
species, especially those which co-occur:
a) during the reproductive phase (bud to recruit, and
including fecundity),
b) during stand development and trough to mortality,
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c) population genetics of selected species under selected
conditions;
3. comparative ecophysiological experiments on seeds
and seedlings; and
4. competition experiments.
The teams exist within the frame of the International
Working Group on Dipterocarps (IWGD-IUFRO S.07-
17 Working Party) and contacts have already been taken
between the authors of this paper and their direct
commentators for this purpose. Field and laboratory
works will be organised on the base of complementarity.
Overall, a cooperative, integrated and detailed reassessment
is needed for the whole family
Dipterocarpaceae sensu lato, with the establishment of
an evolutionary classification based on a general
consensus. Several groups around the world are currently
working on projects that can lead to such a solution. They
include: Forest Research Institute Malaysia, Kepong and
Unité Mixte de Recherche 5558 du Centre National de
la Recherche Scientifique with Lyon University (France),
in association with Harvard University (USA), who are
working on the genetic analysis of DNA sequences;
Massachusetts University (USA) on genetic and breeding
system studies (Murawski and Bawa 1994, Murawski et
al. 1994); and Cambridge-Edinburgh (U.K.) on computer
identification keys (Newman et al. 1995). Several more
complementary works are needed in palynology (pollen
and exine), stamen architecture and shape (the flower
being observed from the pollination point of view),
ontogenesis (structure and morphology of fruit-embryogermination,
anatomy of cotyledonary node and petiole,
epidermis of primordial leaves), wood anatomy,
chemotaxonomy and architecture of juvenile stage. These
complementary works will require broad cooperation
with colleagues and institutions from the Asian, African
and South American zones. More effort is needed for
the Asian dipterocarps from China, Burma and Indo-
China. Likewise, there is a need for contact with African
colleagues
Acknowledgements
We express our sincere thanks to the Center for
International Forestry Research and most particularly to
C. Cossalter for having initiated and supported the
realisation of a book which provides the first broad
synthesis of the present status of knowledge on
dipterocarps that complements the proceedings of the