EUPHORBIACEAE
OF MADAGASCAR
INTRODUCTION
Euphorbiaceae sensulato (s.l. =
in the wide sense)is the sixth largest
plant family in
the
world.
Approximately
700 indigenous species in c. 60 genera
occur in Madagascar. The plants occur
all over Madagascar, in pristine
rain forest as well as in disturbed
habitat, from the Masoala Peninsula
to Toliara. They can be large trees
to small herbs. Because of their
very small flowers, this family is
relatively poorly studied in Madagascar.
These web pages report on the results
of the "Euphorbiaceae of Madagascar" project
at the Royal
Botanic Garden, Kew.
FLORISTIC INVENTORY
Illustration by Catherine Wardrop
reproduced by kind permission. |
RBG Kew is a
major collaborator in the Euphorbiaceae
volumes of the "Flore
de Madagascar et des Comores" which
is coordinated by Dr Gordon
McPherson at the Missouri Botanical
Garden. Other contributing
institutions are the Muséum
National d'Histoire Naturelle,
Paris, and the Canadian
Museum of Nature, Ottawa.
So far, treatments of 26 of
the 60 genera have been produced
including the large genus Croton (150
endemic species in Madagascar)
by Alan Radcliffe-Smith (Kew).
Other major genera are Euphorbia (c.
125 endemic species in Madagascar)
which is the subject of a PhD
thesis by Thomas Haevermans
(MNHN
Paris),
co-supervised by Dr Petra Hoffmann
in Kew. The next biggest and
very difficult group is the
genus Phyllanthus (c.
70 species) which the subject
of a PhD thesis based at the University
of Antananarivo (see below).
During our fieldtrips we still
regularly encounter plants
that are new to science, which
are then described as new species.
One recent example in Euphorbiaceae
is Suregada celastroides Radcl.-Sm. & Petra
Hoffm. from Mt Vatovavy near
Ifanadiana.
Reference: Radcliffe-Smith,
A. , Hoffmann, P, Ranaivojaona,
R.& H. Ralimanana: Suregada
celastroides Radcl.-Sm. & Petra
Hoffm. (Euphorbiaceae), a
new species from eastern
Madagascar, Kew Bulletin,
in press.
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| Hélène in the
Kew office, Tana |
Collecting in Mayotte |
Phyllanthus decipiens (Baill.)
Müll. Arg |
TRAINING AND CAPACITY BUILDING
 As
part of RBGKew's Euphorbiaceae
research, a PhD project entitled
"Systematics and Biogeography of
Madagascan Phyllanthus" started
in 2002 at the Departement
de l’Ecologie et Biologie Végétale,
University of Antananarivo. The
candidate, Hélène RALIMANANA,
has already undertaken several fieldtrips
in Madagascar and Mayotte, as well
as two study visits to the herbaria
of Paris and Kew. She will also participate
in the 17th AETFAT congress
on Tropical African Botany in Ethiopia.
The genus Phyllanthus is
represented in Madagascar by c. 60
species, most of which are endemic,
i.e. they do not occur elsewhere
in the world. The thesis will include
a biogeographical (GIS)
analysis and IUCN
conservation ratings for all
species. A DEA project has commenced
at the same
time on the subject "Etude
systematique et biogeographique de Phyllanthus
casticum et Phyllanthus
nummulariifolius a Madagascar",
undertaken by Bakolinantenaina ANDRIANAIVORAVELONA
and examining the variability of
the closely related taxa in these
two species complexes.
PLANT CONSERVATION
A main objective of Kew's
work is plant conservation. The natural
vegetation of Madagascar is unique
in the world but also highly  endangered
by clearing for agriculture and fire
wood, as well as bush fires. To assess
the threat to plant species, we are
using IUCN threat categories developed
by the World Conservation Union.
The most endangered plants will be
included in the Red List of Threatened
Species. This list is used by decision
makers and NGOs to set priorities
for conservation. Thomas Haevermans
(MNHN
Paris) has
assessed all 166 species, subspecies
and varieties of the genus Euphorbia in
Madagascar, many of which (especially
succulents) are illegally exported
from Madagascar. IUCN conservation
assessments are now a part of most
research at Kew. Recent examples
are the revision of the genus Petalodiscus by
Petra Hoffmann (Kew) and Gordon McPherson
(MBG),
and the forthcoming revision of Phyllanthus by
Helene Ralimanana.
References: Hoffmann,
P. & McPherson, G.: Revision
of Petalodiscus including Blotia (Euphorbiaceae-Phyllanthoideae),
Annals of the Missouri Botancal Garden,
submitted 2002.
PHYLOGENETIC ANALYSIS
RBG Kew is
also working on the evolution of
flowering
plants as a whole. Because Euphorbiaceae
s.l. is one of the largest plant
groups, a collaborative Kew project
with
Austrian and US institutions uses
DNA sequence analysis to study the
relationships within this plant family
worldwide. To apply this technique,
small quantities of quickly dried
leaves are needed. On plant collecting
trips in Madagascar we have collected
important genera such as Antidesma,
Meineckia, Petalodiscus, Thecacoris,
Uapaca, and Wielandia for
this study.
Reference: Wurdack,
K.J., Hoffmann, P, Chase, M. W.,
Samuel, R., de Bruijn, A. & van
der Bank, M. Molecular phylogenetic
analysis
of Phyllanthaceae (Phyllanthoideae
pro pate, Euphorbiaceae s.l.) using
plastid rbcL sequences. American
Journal of Botany in press.
Samuel, R., Katriarachchi, H., Hoffmann,
P., Barfuss, M., Wurdack, K.J. &
Chase, M.W. Molecular phylogeny of
Phyllanthaceae: Evidence from plastid
ma+K and nucleas PhyC sequences.
American Journal of Botany in press.
CONTACT
Petra Hoffmann, Malpighiales Section, Herbarium, Royal Botanic Gardens,
Kew, Richmond Surrey, TW9 3AB, UK. Email
Hélène Ralimanana, R.B.G. Kew ,Lot II J 131 B, Ambodivoanjo
- Ivandry, Madagascar 00101 Antananarivo Email:
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