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The Leguminosae of Madagascar
Madagascar is singled out by the international scientific and conservation community as one of the richest countries in the world in terms of biodiversity, endemism and range of habitats. Its flora is diverse and unique. Of approximately 10,000 native higher plant species, about 8,000 species are thought to be endemic to the island. As a comparison, Madagascar is about 2.5 times as large as Britain, which has about 1,200 plant species, of which only 10--20 are endemic. The value of the flora of Madagascar, both to the local peoples and in a global sense, is potentially immense. Despite its importance, this flora is under serious threat; 80--85 % of the island has already been stripped of its native vegetation cover. Most of this degraded land now supports a very species-poor secondary grassland that is burnt annually and is subject to intense erosion. The heritage of biological diversity in Madagascar is probably under greater threat than in any other country. This unique diversity, combined with the threats to the remaining native vegetation, puts Madagascar amongst the highest conservation priority areas in the world. The new Legume genus Peltiera Labat & Du Puy (1997) is known to have contained two species, both of which already appear to be extinct. This is possibly the first case of a modern genus being described after it has become extinct. Many other species in Madagascar must also be verging on extinction. The Leguminosae of Madagascar project The Leguminosae of Madagascar have never been fully catalogued, with only two, incomplete and unpublished copies of the work of R. Viguier surviving the bombardment of the printing works at Caen during the second world war. This work has provided the basis for a major project at Kew to revise the Leguminosae of Madagascar, in order to fill this gap in our world-wide knowledge about the family. The work has been carried out in collaboration with several botanists from Paris and Antananarivo (notably J.-N. Labat, the late J.-F. Villiers, J. Bosser and R. Rabevohitra). During the course of this review of the Leguminosae of Madagascar, 6 new genera (containing 38 species in Madagascar) and 121 new species have been described. The endemic genus Vaughania, originally only known from 1 obscure species, has been expanded to include 11 endemic species. Revisions of the genera Delonix (Du Puy, Phillipson & Rabevohitra, 1995), Alantsilodendron (Villiers 1994), Phylloxylon (Du Puy, Labat & Schrire, 1995), Vaughania (Du Puy, Labat & Schrire, 1994) and Pyranthus (Du Puy & Labat, 1995) have already been published. The Leguminosae is a large, cosmopolitan family which is important for its many uses from major agricultural food and fodder crops and green manures to medicines and hardwoods. It is also an important family in the flora of Madagascar, with c. 670 species recorded from the island. If the introduced and naturalised species are excluded (c. 105 species, although it is difficult to be sure whether certain species are introduced or native), some 565 native species in 99 genera are known from Madagascar (115--118 species in 13 genera for the Mimosoideae, 85--90 species in 22 genera for the Caesalpinioideae, and 350--360 species in 64 genera for the Papilionoideae). Of these c. 565 native species, 449 are restricted to Madagascar (endemic) or occasionally extend to the Comoros or the Mascarenes (107 in the Mimosoideae, 77 in the Caesalpinioideae and 434 in the Papilionoideae), making a total of c. 80 % of the native species endemic (or near-endemic) to the island. The family is richest and most diverse in the areas with a pronounced dry season, such as occurs in the south, the west and the northern tip of Madagascar, where it can commonly play a dominant or important role in the vegetation. It is less species-diverse and less important in the composition of the humid evergreen forests of eastern Madagascar, although woody genera such as Albizzia, Dichrostachys, Viguieranthus, Baudouinia, Cynometra, Dialium, Intsia, Cordyla, Dalbergia, Millettia, Mundulea and Phylloxylon are represented and can play an important role as emergent, canopy or understorey trees, and canopy lianes such as Strongylodon, Entada and Leucomphalos also occur. The forest on the eastern coastal plains has a larger element represented by this family than the mid- or upper altitude forests. In recent cladistic research on the evolution of the tribe Indigofereae, Barker et al (2000). have shown that two genera endemic to Madagascar (Phylloxylon and Vaughania) were amongst the first genera to diverge manner from the line of evolution in the tribe Indigofereae which gave rise to the extremely large genus Indigofera. Examples such as this shed light on the sequence of evolution of the Leguminosae, and the geographical questions of where this evolution took place. In this context, it is interesting to note that the island of Madagascar split off from mainland Africa about 133 million years ago, but remained joined to India until finally that also split away about 88 million years ago. Since then, Madagascar appears to have had a relatively stable climate, perhaps allowing the survival of some primitive groups which do not now occur elsewhere, and also allowing in that period of time the evolution of a number of distinct genera and numerous species. Of the 22 genera
which are recognised as being endemic to Madagascar,
8 contain only one species (monotypic); 6 of
these latter are in the subfamily Caesalpinioideae.
Interesting and useful genera of Leguminosae in Madagascar Many species in the Leguminosae of Madagascar have local uses or other interesting aspects, some of which are presented below. The genus Delonix in the Ceasalpinioideae contains the well-known and widely planted Flamboyant tree, Delonix regia, which originates from northern and western Madagascar. Its scarlet flowers and fern-like foliage are a common sight in tropical streets and gardens. Other species of Delonix in Madagascar have a distinctive swollen, cigar- or bottle-shaped trunk, used for dug-out canoes, and are distinctive of some arid areas. Colvillea and Lemuropisum are closely related monotypic genera from Madagascar. Colvillea racemosa is another highly ornamental species, with large panicles of waxy orange flowers. Lemuropisum edule, restricted to a very small area of the southern tip of Madagascar, provides a local food crop when the beans are immature, and has potential as a high protein food crop in arid regions. Bauhinia monandra, like Delonix regia, is widely cultivated as a decorative plant in tropical gardens. The country of origin of these showy, cultivated species has remained a mystery, particularly for Bauhinia monandra which had been thought to originate from Burma where it was originally described from a cultivated plant. Both species have been demonstrated to have originated from Madagascar. Dalbergia, with 43 species, is noted for its very high quality rosewoods, and is important locally in providing good quality wood for house construction, carpentry, firewood, carving and many other uses (including carts, spears and tool handles). Several other genera also give good quality hardwood, including Cynometra, Intsia, Cordyla, Dialium and Albizzia, whilst the wood of Phylloxylon is extremely hard and dense, far too much so to be worked except as tool handles and in the strain-bearing parts of bullock carts. Baudouinia fluggeiformis has one of the most unusual woods, known as the ‘King’s Wood’ (Manjakabenitany), the trunk and branches very deeply folded, with dark blackish brown wood in the centre and whitish wood on the ends of the ridges only. It is believed to have mystical qualities, and is now used to make ornaments and walking sticks. Tamarindus indica, the ‘Kily’ tree, often has religious sites often associated with large specimens. It is also an important species for shade in villages. The tangy pulp of the fruit is used to make a refreshing drink, for flavouring in cooking and for medicinal uses. The leaves and fruit supply a major food source for Lemurs, especially in the seasonally dry west and south where this tree grows in almost pure stands along rivers, and where it is one of the few trees to retain its leaves and provide good forage during the dry season. Erythrophleum couminga, due to extremely toxic properties, is also seen as highly mystical, and is generally feared, revered and rumours abound concerning the location of individuals. Only the local ‘ombyasa’ dare to approach the tree, which is often said to be surrounded by the skeletons of small birds which have been killed, especially during the flowering season when the smell of the flowers is reputed to be poisonous. It is often difficult to find someone who will point out the ‘Komanga’. Brenierea insignis,
a relative of the showy genus Bauhinia,
has a growth habit with very reduced leaves,
and flattened, cladodinous stems which is coral-like,
silvery grey and very attractive for cultivation.
A similar growth form also occurs in diverse
groups of the Leguminosae in Madagascar, such
as Indigofera (compressa), Vaughania (pseudocompressa), Mundulea (phylloxylon),
and several species of Phylloxylon. Mapping species distributions, vegetation types and patterns of biodiversity A database of the collections of Papilionoid Legumes in Madagascar has been used in a pilot project to examine the possibilities which computer mapping and Geographical information Systems (GIS) could have on the floristic and revisionary work done in the Herbarium at Kew. A database giving the co-ordinates of each collection locality is used to make a distribution map for each species, with one point marking each record. The species distribution map can then be compared with other map layers in the system, such as altitude, substrate, climate or vegetation type. The results have given much greater precision of altitudinal ranges, substrate preferences (both usually little more than an educated guess on specimen labels) and data on other ecological parameters which dictate the distribution patterns of the species. These ecological parameter preferences, when considered in unison, can be used to predict the full possible distribution of a species, eliminating the apparent gaps caused by under-collection in certain areas. A map of remaining primary vegetation in Madagascar has been derived from satellite imagery (Faramalala, 1988 & 1995, Du Puy & Moat, 1996). Using the parameters which seem to have a great effect on species distributions, such as seasonality and substrate (indicated by rock type), the map of remaining primary vegetation has been divided up into vegetation types in a way which reflects the patterns of species distributions (Du Puy & Moat, 1996). It has been possible, using the Papilionoid Legume specimen database, to demonstrate that species distributions do indeed follow the patterns of distribution of the vegetation types demonstrated in the overall vegetation. Distinct preferences can be demonstrated for many species, such as exclusive occurrence in seasonally dry or perennially humid habitats, on a certain geological type such as limestones, quartzites or sand (Du Puy & Moat, 1998). The demonstration that the derived map of vegetation types does indeed reflect the distribution of individual species, and that each type of vegetation will contain its own distinctive range of species, has confirmed the argument that if an area of as many vegetation types as possible is included in reserves, the resulting network of protected areas will contain as large a diversity as possible, not only of Legume species, but of the whole spectrum of the Plant and Animal Kingdoms which make up the biodiversity of Madagascar. These maps and techniques are actively being applied to conservation planning and management of the network of protected areas in Madagascar (Du Puy & Moat, 1998). This project has
demonstrated the practical application of these
techniques to systematics, floristics and conservation,
and it is hoped that they will be further developed
and applied more widely in the future. Please
check out the Madagascar
GIS pages for more information. I would like to
thank in particular J. Bosser, J.-N. Labat,
J. Moat, P. Phillipson, R. Rabevohitra, B.
Schrire and the late J.-F. Villiers, for their
collaboration in this work, and B. Schrire
for his comments on the text. My thanks to
the Weston Foundation for the support of my
research in Madagascar and at Kew, and the
Royal Society for the opportunity to undertake
collaborative research in the Laboratoire
de Phanérogamie, Paris. I am grateful to
the National Geographic Society for support
with field work in Madagascar. I would also
like to thank the Directors and staff of the
Laboratoire de Phanérogamie, Paris, the Herbarium, Royal Botanic Gardens, Kew, the Parc Botanique
et Zoologique de Tsimbazaza, Antananarivo for
their assistance and encouragement, and the
Direction des Eaux et Forêts, Antananarivo
for granting permits for my research. Barker, N.P. Schire, B.D. & Kim, J.-H. (2000) Genmeric relationships in the tribe Indigofereae (Leguminosae-Papilionoideae) based on sequence data and morphology. In Advances in Legume Systematics (P.S. Herendeen & A. Brunean, eds) pp. 311-338. Royal Botanic Gardens, Kew. Du Puy, D.J., Labat, J.-N. & Schrire, B.D. (1994). Révision du genre Vaughania S. Moore (Leguminosae - Papilionoideae - Indigofereae). Bull. Mus. natl. Hist. nat., Paris, 4e sér., 16, section B, Adansonia 1: 75--102. Du Puy, D.J. & Labat, J.-N. (1995). Pyranthus Du Puy & Labat, a new genus of the tribe Millettieae (Leguminosae - Papilionoideae) from Madagascar. Kew Bulletin 50: 73--84. Du Puy, D.J., Phillipson, P. & Rabevohitra, R. (1995). The Genus Delonix (Leguminosae: Caesalpinioideae: Caesalpinieae) in Madagascar. Kew Bulletin 50: 445--475. Du Puy, D.J., Labat, J.-N. & Schrire, B.D. (1995). A revision of Phylloxylon (Leguminosae - Papilionoideae - Indigofereae). Kew Bulletin 50: 477--494. Du Puy, D.J. & Labat, J.-N. (1995-B). A new species of Argyrolobium (Leguminosae - Papilionoideae) from Madagascar. Bull. Mus. natl. Hist. nat., Paris, sér. 4, sect. B, Adansonia, 17: 179 – 181. Du Puy, D.J. & Labat, J.-N. (1996). New species of Erythrina L. and Mucuna Adans. (Leguminosae - Papilionoideae - Phaseoleae) from Madagascar and the Comoros. Bull. Mus. natl. Hist. nat., sér. 4, sect. B, Adansonia 18: 225 – 234. Du Puy, D.J., Labat, J.-N. & Ireland, H. (1997). Two species of Crotalaria L. (Leguminosae - Papilionoideae - Crotalarieae) from central Madagascar. Kew Bull. 52: 443 – 449. Du Puy, D.J. & Moat, J. (1996). A refined classification of the primary vegetation of Madagascar based on the underlying geology: using GIS to map its distribution and to assess its conservation status. In W.R. Lourenço (Ed.), Proceedings of the International Symposium on the Biogeography of Madagascar: 205--218, + 3 maps. Editions de l’ORSTROM, Paris. (Including 3 detailed computer-generated (GIS) maps.) Du Puy, D.J and Moat, J.F. (1998, in press). Vegetation Mapping and Classification in Madagascar (using GIS): Implications and Recommendations for the Conservation of Biodiversity. In: Cutler, D.F., Huxley, C.R. & Lock, J.M. (Eds.), The ecology, chorology and taxonomy of the African and Madagascan floras - Proceedings of the Frank White Memorial Symposium. Kew Bulletin Additional Series. Royal Botanic Gardens, Kew. Faramalala, M.H. (1988). Etude de la Végétation de Madagascar à l’aide des Données spatiales. Doctoral Thesis, Univ. Paul Sabatier de Toulouse, 167 p. + map at 1:1,000,000. Faramalala, M.H. (1995). Formations Végétales et Domaine Forestier National de Madagascar. Conservation International (et al.), 1 map. Labat, J.-N. & Du Puy, D.J. (1994). New species, a new name, and lectotypifications in Indigofera L. (Leguminosae - Papilionoideae - Indigofereae) from Madagascar. Novon 4: 255 – 265. Labat, J.-N & Du Puy, D.J. (1995). New species and combinations in Millettia Wight & Arnott and Pongamiopsis R. Viguier (Leguminosae - Papilionoideae - Millettieae) from Madagascar. Novon 5: 171 – 182. Labat, J.-N & Du Puy, D.J. (1996-A). Two new species of Ormocarpopsis R. Viguier and a new combination in Ormocarpum P. Beauvois (Leguminosae - Papilionoideae) from Madagascar. Novon 6: 54 – 58. Labat, J.-N & Du Puy, D.J. (1996-B). New taxa and nomenclatural changes in Rhynchosia Lour. and Eriosema (DC.) Reichb. (Leguminosae - Papilionoideae - Phaseoleae) from Madagascar and the Comoro Islands. Bull. Mus. natl. Hist. nat., Paris, sér. 4, sect. B, Adansonia 18: 85 – 96. Labat, J.-N & Du Puy, D.J. (1997-A). A revision of Peltiera, a new, poorly known and probably extinct genus of Leguminosae (Papilionoideae - Aeschynomeneae) from Madagascar. Adansonia, sér. 3, 19: 85 – 91. Labat, J.-N & Du Puy, D.J. (1997-B). New species and varieties in Sesbania (Leguminosae -Papilionoideae - Robinieae) from Madagascar and the Comoro Islands. Adansonia, sér. 3, 19: 93 – 99. Labat, J.-N & Du Puy, D.J. (1998). Sylvichadsia, a new genus of Leguminosae - Papilionoideae - Millettieae endemic to Madagascar. Adansonia, sér. 3, 20: 163 – 171. Viguier, R. Villiers J.-F., (1994). Alantsilodendron Villiers, genre nouveau de leguminosae-Mimosoideae de Madagascar. Bull. Mus. natl. Hist. nat. Paris, série 4 sect B, Adansonia 16:65-70 |
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A revision of the Leguminosae of Madagascar has now
been published (