A review of dipterocarps - Center for International Forestry Research

Biogeography and Evolutionary Systematics of Dipterocarpaceae
from one part, and Dryobalanops from the other, could
also enter this evolutionary-limited-potential group.
Sunaptea, having been several times merged into
Vatica, requires fossil and living distributions. The
Sunaptea morphological and anatomical characters in
embryos, fruit-seeds and seedlings could have had a much
larger distribution. The same remarks concern
Cotylelobium. Kostermans (1992) changed
Cotylelobium scabriusculum (Thw.) Brandis into
Sunaptea scabriuscula (Thw.) Brandis. Perhaps
information on living and fossil dipterocarps from China,
Indo-China and Burma could modify the present
perception of their extension. It is also unknown whether
the Vaticoxylon were of the Vaticae, Pachynocarpus or
Sunaptea types. The absence of Cotylelobium among
fossil forms results from a lack of detailed criteria in
wood anatomy that prevents assessment of its presence.
Close cooperative works between paleobotanists,
wood anatomists of living forms and systematicists are
needed to consolidate present conclusions on the mixed
taxa of Vatica and Cotylelobium. Future work should
particularly consider separately the Sunaptea, Vaticae
and Pachynocarpus. The same treatment is necessary
for the Shorea and Hopea sections. These remarks are
especially pertinent for the new molecular approaches
being rapidly developed, and which have been applied in
a few instances to dipterocarps (e.g. Chase et al. 1993,
Wickneswari 1993). Some of the diverse opinions, in
all disciplines, are due to the studies being limited to a
restricted number of species. It is therefore necessary
to examine the whole set of species instead, with
particular attention to intermediate ones such as Vatica
heteroptera and V. umbonata group. The V. pauciflora
(ex V. wallichii) case has already been mentioned above,
together with Shorea roxburghii (ex S. talura). Maury-
Lechon’s previous conclusions (Maury 1978, Maury-
Lechon 1979a, b: Fig. 16, p.100) based on cotyledonary
shapes and structures have been vindicated by
Wickneswari’s results (1993: Fig. 1). These conclusions
concern affinities between the Sunaptea group and
Cotylelobium and their joint affinities with Upuna, as
well as the connection of these three taxa with the
closely related group of Anisoptera first, and then
Dipterocarpus and Dryobalanops. Shorea bracteolata,
the only Anthoshorea in Wickneswari’s study, has
cotyledonary characters that are distinct from species
such as S. roxburghii and S. resinosa (Maury 1978,
Maury-Lechon 1979 a, b, Maury-Lechon and Ponge
16
1979). Consequently, the position of S. bracteolata
reflects perhaps only partially the position of the whole
group of species presently included within the
Anthoshorea. Shorea resinosa and S. roxburghii
cotyledonary shapes locate the Anthoshorea close to
Doona and to Dryobalanops, Dipterocarpus and
Cotylelobium. The present heterogeneity of
Anthoshorea suggests the need for a re-examination both
by DNA analysis and other approaches.
The Dipterocarpus genus should also be examined
for eventual correspondence between chemotaxonomic
groups (Ourisson 1979) and biological characters such
as seed sensitivity to desiccation and cold temperatures,
seed and seedling resistance to pathogens by defensive
secretions, and chemical type of root exudates for
mycorrhizal fungi association. The statement that there
is no relation between chemical groups and
morphological features should be re-examined in
considering flower characters, particularly stamen
shapes, pollen and pollination, sexual and non-sexual
reproduction, the fruit-seed-embryo-seedling sequence
and the habitat.
Phytogeographical Regions of Extinct
Dipterocarps or Related Taxa
No living or extinct monotoid (Tables 5 and 6) has been
reported in Asia while diverse supposed dipterocarpoid
fossils are described from Europe: Woburnia porosa
wood from Bedfordshire Lower Cretaceous, U.K.
(Stopes 1912, Kraüsel 1922, Schweitzer 1958, all in
Aubréville 1976), flowers of Monotes oeningensis
(Heer) Weyland from Upper Eocene in Hungary
(Boureau 1957, Boureau and Tardieu-Blot 1955), and
Tertiary fruits of west Germany, Switzerland and Austria
(Gothan and Weyland 1964, in Aubréville 1976). Doubts
were cast on these identifications (Bancroft 1933, Harris
1956 and Hughes 1961 in Aubréville 1976, Gottwald and
Parameswaran 1966, 1968). Other doubtful fruits of
Monotes type have even been reported from New York
(USA) and from the Alaska Eocene putative but unlikely
tropical forest (Wolffe 1969, 1977).
Boureau (in Boureau and Tardieu-Blot 1955) doubted
this sequence but he remained convinced of the real
presence of Monotes in the European Cretaceous and
Tertiary. Huge distances would then separate the living
Monotoideae from the extinct ones, and the Asiatic-
Malesian Dipterocarpaceae from the European fossils,
without any fossils in between, notably in North Africa.