A review of dipterocarps - Center for International Forestry Research

Biogeography and Evolutionary Systematics of Dipterocarpaceae
Tertiary dipterocarp fossils have been reported from
the African Miocene of Ethiopia (Beauchamp et al.
1973, Lemoigne 1978, Laveine et al. 1987) and from
the putative (but probably earlier) Plio-Pleistocene of
Somalia (Chiarugi 1933). That is in a continent where
not a single living dipterocarpoid has been found, and
where present monotoids are living. Lemoigne (1978,
p.123) specifies ‘c’est avec des bois de la famille des
Dipterocarpaceae, notamment ceux du genre Monotes
que notre echantillon parait avoir le plus d’affinites...
Certes les affinites avec la famille des Lauraceae sont
aussi remarquables’. In spite of its name
Dipterocarpoxylon, this fossil is thus of a Monotoid
type (not Dipterocarpoid). In this case, is the African
rain forest species Marquesia excelsa derived from a
common ancestor with Monotes and adapted to a more
humid climate, or is it the only surviving species of some
Dipterocarpoid ancestor which could have fossilised in
Ethiopia and Somalia (and Egypt?)? A study of the pollen
exine structure in Marquesia is needed to clarify this
genus situation, as well as a critical re-examination of
all dipterocarpoid fossils (doubtful or not).
Numerous accepted fossils from Asia (Awasthi 1971)
testify that the present great species richness of the Asian
flora (Table 6) probably existed since the Miocene and
persists through the Pliocene and Pleistocene, up to the
Quaternary (Anisopteroxylon, Dipterocarpoxylon,
Dryobalanoxylon, Hopenium, Shoreoxylon,
Vaticoxylon, Vaterioxylon).
These fossils demonstrate a reduction of dipterocarp
distribution area both in Africa (Fig. 1, Tables 5 and 6)
and Asia (extinction of Anisoptera and Dryobalanops
in India, and of the latter in Indo-China), and total
extinction in Europe and North America (doubtful
fossils?). Could thus the Tertiary distribution area of
dipterocarps sensu stricto include Africa and Asia (and
Europe?)?
Hypotheses on the Geographical Origin of
Dipterocarpaceae
If Monotoideae and Pakaraimaea are to be connected
to Asian dipterocarps (by a single family or into different
families), a common ancestor and its migration path have
to be found. During the transition from the later
Cretaceous to the very early Eocene the paleogeographic
changes, in combination with other effects, could have
produced the present geography. Thus dipterocarp
ancestors should have been present when land
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connections still existed between South America, Africa
and India and between them and southeast Asia (and
probably with the European and north American Laurasia
block with its intermittent ‘Grande coupure’). This
situation occurred (Figs. 2 (A, B), 3) in the Permo-
Triassic period. Later, parts of the northeastern Gondwana
land detached from the Gondwana shelf, crossed the
Tethys and joined southeast Laurasia (just as India would
do later). These changes would have happened during the
Permo-Triassic, Jurassic and Cretaceous times according
to recent works on Cathaysian floras (Kovino 1963,
1966, 1968, all in Vozenin-Serra and Salard-Cheboldaeff
1994, Lemoigne 1978, Jaeger et al. 1983, Vozenin-Serra
1984, Vozenin-Serra and Taugourdeau-Lantz 1985,
Laveine et al. 1987, Taugourdeau and Vozenin-Serra
1987, Renous 1989, Scotese and McKerrow 1990 in
Vozenin-Serra and Salard-Cheboldaeff 1994), and on the
Tethys Sea (Dercourt et al. 1992).
Croizat (1964, 1952 in Aubréville 1976) and Ashton
(1969) expressed the view of a dipterocarp Gondwanan
origin of the present distribution area and to a further
migration towards Indo-Malesia. Aubréville (1976)
considered that Dipterocarpaceae probably occupied two
main areas before the Cretaceous general drift of
Gondwanan shelves: one in Asia and one in the joined
Africa-India-Seychelles-Sri Lanka complex. He believed
that the origin was in Europe from where ancestors of
monotoids would have migrated towards Africa and
further from there to India. He suggested two Tertiary
centres of dipterocarps: one Indo-Malesian from
Laurasian origin; and one Africano-Indian from a
Gondwanan origin, on both sides of the Tethys Sea. More
recent studies (Renous 1989, Dercourt et al. 1992,
Vozenin-Serra and Salard-Cheboldaeff 1994) identify
direct land connections between southeast Asia and
Laurasia lands. These authors consider a possible series
of small blocks detached from the northeastern part of
Gondwana, moving through the Tethys, and forming an
archipelago (Fig. 3: Tazrim-Sino-Korean block (1), north
China block (2), north Tibet block (3), Khorat-Kontum
block: east Thailand and most parts of Laos, Cambodia
and Vietnam (4), south Tibet block (5), Kashmir block
(6), Iran-Afghanistan block (7), Turkey block (8), Spain
block (9)) together with the different southeast Asian
plates. This putative archipelago would have served as a
relay, perhaps owing to volcanism which would open
routes for floral migration. Before the rise of the
Himalayas, floristic exchanges would also have been
possible around the Tethys (Dercourt et al. 1992).