Melia L.

Trees, treelets or rarely shrubs, dioecious, polygamous, monoecious or all flowers hermaphrodite. Indumentum of simple or stellate hairs, stellate or peltate scales, sometimes mixed. Vegetative buds naked or with scale-leaves (in Australia only in subfam. Cedreloideae). Leaves exstipulate, spirally arranged, rarely decussate, pinnate (sometimes with a terminal ‘bud’, i.e. pseudogemmula) to simple or bipinnate; leaflets usually entire. Inflorescences thyrsoid to spicate, fascicled or of simple flowers, axillary to cauliflorous or epiphyllous (not in Australia). Calyx of discrete sepals, sometimes transitional to bracteoles, or a tube, sometimes atop an elongate pseudopedicel. Petals usually in 1 whorl of 3–7. Stamens free or usually anthers borne on or in a tube; anthers usually 3–10 in 1 whorl. Disc (probably nectary) around ovary or absent. Ovary usually 2–6-locular, each locule with 1–many ovules. Fruit a capsule, berry or drupe. Seed with fleshy aril or sarcotesta or combination of these, or winged or corky or none of these; endosperm usually absent.

A family of 50 genera and about 650 species throughout the tropics and subtropics with very few in temperate regions; in Australia 13 genera (2 endemic, 2 naturalised) and 44 species (14 endemic). A number of exotic species are grown for timber, fruit and ornament, and 2 are known to be naturalised.

Many Meliaceae are very common trees of the canopy and understorey of lowland primary forest throughout Indomalesia and the western Pacific; they are represented by species of Xylocarpus on rocky shores and in mangrove swamps but are poorly represented at high altitudes; some species of Owenia, a genus restricted to Australia, are notable for occupying arid regions. Many are early successional species surviving into the mature canopy of rainforest and are frequent in regrowth. Most species appear to be insect-pollinated and the seeds of Melioideae animal-dispersed. In Australia, birds are important dispersal agents of seeds from capsular fruits, berries and drupes, those of Owenia probably being dispersed by emus. Of Cedreloideae, the winged seeds are wind-dispersed and the corky seeds of Xylocarpus are dispersed by ocean currents.

The timbers of certain Meliaceae are some of the most sought after in the world, such that natural stands have been much depleted. The original ‘mahogany’ of 18^th Century English furniture-makers Hepplewhite and Chippendale was Swietenia mahagoni (L.) Jacq. of the neotropics, which allowed the manufacture of more graceful and woodworm-proof furniture than could the oak and walnut previously utilised in Europe: this species has suffered severe genetic erosion and most ‘mahogany’ seen today (if meliaceous at all) is derived from S. macrophylla King, introduced to the Old World in 1876 and described from cultivated material in India. Toona ciliata M.Roem., Red Cedar, has suffered similarly (see below). The other important meliaceous timbers are generally Cedreloideae, notably the neotropical Cedrela odorata L. and species of the African genera Entandrophragma (Sapele, Utile), Khaya (African Mahogany) and Lovoa (Nigerian Golden Walnut). In Australia, where the timbers of Melioideae are generally known as Rosewood, the most important are in the genus Dysoxylum, which includes fine timber species in Indonesia and New Zealand as well. Although a number of species have been tried in plantations in Australia and elsewhere, there are very serious problems due to the depredations of Hypsipyla moths, the larvae of which are pernicious shoot-borers.

A number of Malesian Meliaceae are valuable fruit trees, notably the Langsat and Duku, cultivars of Lansium domesticum Corrêa, and the Sentul, Sandoricum koetjape (Burm.f.) Merr., a species grown in Queensland. More important on a world scale are Azadirachta indica A.Juss. as a soil ameliorant and source of innumerable by-products (see below) and Melia azedarach L. as a source of insecticides and second quality timber (see below). The bitterness of the barks of many Meliaceae has long been known and they are of considerable importance in local medicine in Indomalesia, where European settlers eagerly sought them as possible antimalarials: they are now receiving renewed interest. Besides aboriginal use as fish-poisons (Melia) and for food (fruits of Owenia species), Australian Meliaceae are otherwise only utilised as shade-trees for stock and for ornament.

Exotic species grown in plantation include the neotropical Cedrela odorata L., cultivated in Queensland and New South Wales for timber and as a street-tree; it is becoming naturalised in the Old World, as, for example, in New Caledonia, and may be expected to do so in Queensland. It yields one of the most important tropical hardwoods. The neotropical true mahoganies are in plantation in the Old World, including Queensland: Swietenia macrophylla King is the principal source of present-day mahogany, considered one of the most valuable timbers for cabinetwork. Other exotics, particularly African species of Turraea and Khaya, are grown in private and botanic gardens. Khaya senegalensis is recorded from two Aboriginal communities in the Kimberley region of Western Australia. One record describes the species as abundant in a disturbed area in and around houses, forming a woodland of this species. It could easily become naturalised from this population.

The family is divisible into two pantropical subfamilies, Melioideae and Cedreloideae (Swietenioideae), both being represented in Australia. The family is chemically marked by the presence of extremely characteristic tetranortriterpenoids called limonoids, of which over 250 were identified before 1984. Those of Australian Meliaceae are discussed by Mulholland and Taylor (1992). They have also been found in Cneoraceae (now included in Rutaceae), some Rutaceae and Harrisonia R.Br. ex A.Juss. (generally put in Simaroubaceae but now accommodated in Rutaceae). Several limonoids constitute the principal toxins of the plants and are of considerable commercial interest (see Azadirachta and Melia below). The structure of limonoids in different genera gives general support to the morphological classification but draws attention to the debated position of tribe Xylocarpeae (Cedreloideae) and the finely drawn distinctions between certain tribes of Melioideae. DNA sequencing (Muellner et al. 2006) places Xylocarpeae in a clade with most Cedreloideae and does not reflect the Pennington and Styles (1975) classification in so far as the two unigeneric subfamilies from Madagascar they propose are deeply embedded in the two subfamilies recognised here, while their concept of tribes such as Trichilieae and Turraeeae is not reflected in the molecular classification. Muellner et al. conclude that the family had a west Gondwanan origin.

At the generic level, the family demonstrates some remarkable transpacific affinities: Old World Toona with neotropical Cedrela and Old World Dysoxylum and Chisocheton with neotropical Guarea L. Fossils with features which would put them in modern Meliaceae if they existed today are known from the Upper Cretaceous, some of the earliest being referred to Guarea, while, of the Cedreloideae, ‘Cedrela’ is recorded from the Palaeocene and ‘Toona’ from the Eocene of Britain (London Clay).

Flindersia R.Br., included in this family by Bentham (1863), is now referred to Rutaceae.

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Cheek, M.R. (1989). The Systematic Seed Anatomy of the Meliaceae with Particular Reference to the Seedcoat of the Melioideae, Doctorate of Philosophy Thesis (Bodleian Library: Oxford).

da Silva, M.F. das G.F., Gottlieb, O.R. & Dreyer, D.L. (1984). Evolution of limonoids in the Meliaceae. Biochemical Systematics and Ecology 12: 229–310.

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Muellner, A.N., Savolainen, V., Samuel, R. & Chase, M.W. (2006). The mahogany family “out-of-Africa”: divergence time estimation, global biogeographic patterns inferred from plastid rbcL DNA sequences, extant, and fossil distribution of diversity. Molecular Phylogenetics and Evolution 40: 236–250.

Mulholland, D.A. & Taylor, J.A.H. (1992). Limonoids from Australian Members of the Meliaceae. Phytochemistry 31: 4163–4166.

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