| Lauraceae | |
|---|---|
| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Angiosperms |
| (unranked): | Magnoliids |
| Order: | Laurales |
| Family: | Lauraceae |
| Genus: | Ravensara |
| Species | |
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See text. |
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The Ravensara is a Madagascar endemic genus of trees and shrubs flowering plants belonging to the family Lauraceae. Ravensare species produce Essential Oils from their bark, their leaves and their fruit. The genus is composed of species native to central and eastern Madagascar. In a recent generic classification of Lauraceae based on DNA sequence data by Chanderbali et al. in 2001, was found to be part of a strongly supported clade that also includes Beilschmiedia, Potameia, Cryptocarya, Endiandra and Aspidostemon.[1]
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The best known kind of Ravensara is Ravensara aromatica. The essential oil extracted from its leaves is used for its medicinal properties. In Madagascar this genus of trees are commonly called Hazomanitra, tree that smells.They named local bark of Ravensara anisata Havozo. Ravensara is a genus of evergreen laurel species that include currently more than 10 species, mostly in laurel forest habitat. The genus Ravensara, endemic to Madagascar, was described by Sonnerat in 1782 with the single species Ravensara aromatica. Kostermans maintained Ravensara in his treatment of the Lauraceae for the "Flore de Madagascar et des Comores" and in a later publication from 1958 in which he described an additional nine new species of Ravensara. Currently, the estimated number of species of Ravensara is about 30. Ravensara has always been considered closely related to Cryptocarya. The malgache species placed in Ravensara and Cryptocarya are still poorly known, a transfer of all Ravensara species to Cryptocarya is not justified once revised the DNA isolation. Fisically in Ravensara the fruits are ruminate, whereas in malgache Cryptocarya they are not.
The genus includes species of evergreen trees, endemic from Madagascar and Comoro Islands. The evergreen trees or shrubs in genus Ravensara are massive broad leaved evergreen trees growing 30 m tall. or slightly enlarged. Common canopy trees to 30 m, sometimes very large to 60 m. or subcanopy trees in the succession climax species in tropical, lower temperate or subtropical broadleaved forest. Across communities of evergreen broadleaved forest and mixed coniferous-broadleaved forest. Found in low elevation evergreen forests and littoral rainforest, usually on all type of soils.
The trunk itself can grow to over a meter in diameter. Twigs angular, glabrous, terminal buds densely and minutely puberulous. The leaves are dark green and shiny. The leaves are alternate, obovate to obovate-elliptic, 6-11 × 3–6 cm, glabrous, stiffly coriaceous, the base acute, rarely obtuse, margin flat, the apex rounded, the lower surface minutely but densely gland-otted, lateral veins 4-6 on each side, reticulation raised on both surfaces, petioles glabrous, 9–14 mm long. Inflorescences 3.5–9 cm long, paniculate, branched from the base, glabrous; bracts along inflorescences mostly deciduous, 1.5 mm long, linear, pubescent. Flowers yellow-green, externally glabrous, tepals initially half-erect, in old flowers spreading, flowers 4–5 mm in diameter; pedicels short, from half the length of the floral tube to equaling it; having six tepals equal, narrowly ovate, 1.5–2 mm long, glabrous outside, puberulous inside; stamens 9, all 2-celled, pubescent, c. 1 mm long, the filament very short, 0.1-0.2 mm, the anther cells large, the connectives slightly prolonged beyond the anther cells; stamens with the same length and width as the tepals and hidden behind them; 2 small globose glands present at the base of the inner three stamens; staminodia small, narrowly ovate, pubescent; pistil glabrous, the style to 1 mm exserted, receptacle tubular, pubescent near the rim, otherwise glabrous. Fruits are fleshy. The fruit, a berry, are an important food source for birds, usually this birds are from specialized genus: Columbidae, Turdidae, etc. Seeds are spread by birds. Birds eat the whole fruit and regurgitate seeds intact, expanding the seeds in the best conditions for germination (ornitochory).
Only two species of Ravensara have the combination of glabrous twigs and leaves and raised reticulation on both surfaces of the leaves. Of these two, Ravensara macrophylla, only known from the fruiting type, differs in leaf shape (elliptic) and size (16–20 cm long). Like R. glabriflora, it has glabrous flowers, a feature unknown in other members of the genus on Madagascar, although flowers are unknown in 13 species.
This genus reported for Madagascar and Comores Islands, have differences resultanting in ecological adaptations to different environments over a relatively dry-wet climate. Species in less humid environment are smaller or less robust, with less abundant and thinner foliage and have oleifera cells that give trees a more fragrant aroma. The Ravensara genus has led to endemic species on islands, but not so widespread geographically as in the past.
Ravensara genus is becoming endangered. Due to the low density, exploitation of the natural populations is in the detriment of the rainforest. The Ravensara genus is included in the Cryptocarya within the Lauraceae family, by Ravensara oil proposes. Some species have been used for a long time to produce essential oils for the pharmaceuticals industry.
The ecological requirements of the genus, are mostly those of the laurel forest and like most of their counterparts laurifolia in the world, they are vigorous species with a great ability to populate the habitat that is conducive. Machilus responded to favourable climatic periods and expanded across the available habitat. The main centers are found inhabiting wet lands in tropical or subtropical montane forests or coastal rainforest or coastal temperate forest in low-altitude. The islander Ravensara species can not enduring the bad winter, from continental climate. Those garden cultivated species outside its natural distribution could be killed by continental winter.
It contains the following species, but this list is incomplete: