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''Simarouba amara'' is a species of tree in the Simaroubaceae family, found in the rainforests and savannahs of South and Central America and the Caribbean. It was first described by Aublet in French Guiana in 1775 and is one of six species of ''Simarouba''. The tree is evergreen, but produces a new set of leaves once a year. It requires relatively high levels of light to grow and grows rapidly in these conditions, but lives for a relatively short time. In Panama, it flowers during the dry season in February and March, whereas in Costa Rica, where there is no dry season it flowers later, between March and July. As the species is dioecious, the trees are either male or female and only produce male or female flowers. The small yellow flowers are thought to be pollinated by insects, the resulting fruits are dispersed by animals including monkeys, birds and fruit-eating bats and the seeds are also dispersed by leaf cutter ants. ''Simarouba amara'' has been studied extensively by scientists in an attempt to understand the tree and also to gain a better understanding of the ecology of the rainforest in general. Many of these studies were conducted on Barro Colorado Island in Panama or at La Selva Biological Station in Costa Rica. Of particular interest is how it competes with other species and with individuals of the same species at different stages in its life cycle. The seedlings are normally limited by the amount of light and nutrients found where they are growing and the saplings are considered relatively light demanding compared to other species. Young individuals are more likely to survive when they grow further away from their parents and when there are few other individuals growing near to them, which may be due to them being able to escape diseases. Plant physiologists have investigated how the leaves of the tree differ depending on their location in the forest canopy finding they are thicker in the canopy and thinner in the understory. They have also measured how the water potential of their leaves changes and when their stomata open and close during the day; the findings suggest that rather than closing their stomata to control water loss, it is controlled by the leaf area instead. Population geneticists have examined the way in which its genes vary, at both the local scale and across its range using microsatellites. It is genetically diverse, indicating gene flow occurs between populations and seeds can be dispersed up to 1 km. The leaves of ''S. amara'' are eaten by several species of caterpillar, particularly those in the ''Atteva'' genus. Several species of termite and ants live on or around the tree and lianas and epiphytes grow on the tree. The bark of ''S. amara'' has been used by people in its range to treat dysentery and diarrhea, as well as other diseases, and was also exported to Europe in the eighteenth century to treat these illnesses. A number of compounds have since been isolated from the bark and have been shown to have antimicrobial effects. Local people use the wood of the tree for various purposes and it is also grown in plantations and harvested for its timber, some of which is exported. ==Description== ''Simarouba amara'' grows to heights of up to 35 metres, with a maximum trunk diameter of 125 cm and a maximum estimated age of 121 years. It has compound leaves that are each around 60 cm long, the petioles are 4–7 cm long and each leaf has 9–16 leaflets. Each leaflet is 2.5–11 cm long and 12–45 mm wide, with those towards the end of the compound leaf tending to be smaller. The flowers occur on a staminate panicle that is around 30 cm in length, which is widely branched and densely covered in flowers. The flowers are unisexual, small (<1 cm long) and pale yellow in colour. They are thought to be pollinated by insects such as small bees and moths. On Barro Colorado Island (BCI), Panama, it tends to flower during the dry season from the end of January to the end of April, persisting for 11 to 15 weeks each year.〔 In Costa Rica, it flowers slightly later, between March and July, peaking in April. Fruits form between 1 and 3 months after pollination occurs. The fruits are brightly colored green to purplish-black, approximately 17 mm long and contain large seeds (10–14 mm), they occur in groups of 3–5 drupes. The seeds cannot stay dormant and are dispersed by vertebrates.〔 Each seed weighs approximately 0.25 g.〔 It is an evergreen species, with a new flush of leaves growing between January and April, during the dry season, when the highest light levels occur in the rainforest. This phenology is thought to allow ''S. amara'' to photosynthesise most effectively, since the new leaves are more efficient than those they replace.〔〔 It has visible, but indistinct growth rings that are on average 7 mm wide.〔 A study of individuals in Panama found that they grow on average 8.4 mm in diameter each year, in Costa Rica, growth rates as fast as 18 mm per year have been recorded, and the stem grows constantly throughout the year.〔 The xylem vessels in mature trees range from 20 to 90 μm in diameter, with around 50 vessels present per mm2 of branch. The density of the wood is between 0.37–0.44 g/cm3,〔 lower than many other species in the rainforest. It is a fast-growing, light-demanding and shade-intolerant species. Saplings are typically one straight pole, with several compound leaves and only one point of growth. This allows the sapling to achieve the greatest vertical growth with a minimum amount of biomass. They start to branch once they are 2–5 m tall. A study in the forest dynamics plot on BCI found that between 1982 and 2000, around 65% of individuals died, with mortality highest amongst small individuals (<1 cm dbh). Large trees (>20 cm dbh) are relatively rare, averaging 2.4 trees per hectare, compared to 40 trees per hectare of >1 cm dbh.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Simarouba amara」の詳細全文を読む スポンサード リンク
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