Milicia excelsa

Milicia excelsa is a tree species from the genus Milicia of the family Moraceae. It is one of two species (the other being Milicia regia) yielding timber commonly known as African teak, iroko, intule, kambala, moreira, mvule, odum and tule. African teak is distributed across tropical central Africa. Its range extends from Guinea-Bissau in the west to Mozambique in the east. It is found in Angola, Benin, Burundi, Cameroon, Central African Republic, the Republic of the Congo, the Democratic Republic of the Congo, Equatorial Guinea, Ethiopia, Gabon, Ghana, Ivory Coast, Kenya, Malawi, Mozambique, Nigeria, Rwanda, São Tomé and Príncipe, Sierra Leone, Sudan, Tanzania, Togo, Uganda and Zimbabwe. Its natural habitat is in wet savannah, rainforest, riverine and low-altitude evergreen forests. It can tolerate an annual rainfall of less than 70 centimetres (28 in) or six months of drought as long as there is a stream or a ground water source nearby. In a study done on population distribution of Milicia excelsa in 2009, researchers found that most of the populations that were being studied were inbred. After some analysis the researchers found that the Milicia excelsa was inbreeding due to lack of proximity to other Milicia excelsa individuals. Inbreeding could contribute to why this species is moving closer to being on the “Threatened” conservation list. If the numbers of mates available are not high enough because dispersion methods are not effective over long distances, then the species will begin to suffer from inbreeding depression (inbreeding can lead to accumulation of recessive deleterious alleles in a population). The species is a large deciduous tree growing up to 50 metres (160 ft) high. The trunk is bare lower down with the first branch usually at least 20 metres (66 ft) above the ground. It often has several short buttress roots at the base. The bark is pale or dark grey, thick but little fissured, and if it gets damaged it oozes milky latex. There are a few thick branches in the crown all fairly horizontal giving an umbrella shape. The smaller branches hang down in female trees and curve up in male trees. The leaves are 5 to 10 centimetres (2.0 to 3.9 in) long, ovate or elliptical with a finely toothed edge, green and smooth above and slightly downy beneath. Older leaves turn yellow, and all of the leaves have a prominent rectangular mesh of veins visible on the underside. The trees are dioecious. Male trees have white catkins that extend 15 to 20 centimetres (5.9 to 7.9 in) and dangle from twigs at the axils of the leaves. Female trees have flower spikes measuring 5 to 6 centimetres (2.0 to 2.4 in) long by 2 cm (0.8 in) wide, green with prominent styles. The fruit are long, wrinkled and fleshy with the small seeds embedded in the pulp. There is evidence that some of the variation that is described above amongst individuals is due to the variation in the environment. In a study done in 2010, it was found that environmental change from different regions in Benin caused much of the variation in Milicia excelsa. Many studies have attributed this variation in growth to the differences in climate of regions. Specifically, soil characteristics and rainfall played a major role in the morphological variation of trunk growth of Milicia excelsa. Milicia excelsa is one of two tree species (the other being Milicia regia) that yield timber commonly known as African teak. Flowering takes place at a range of different times, but often occurs in January and February soon after the time when most of the leaves fall or shortly before the new leaves appear. The fruits take about a month to ripen and are eaten by squirrels, bats, and birds, which then disperse the seeds in their droppings. Some populations, especially plantations, are attacked by a gall mite. A study in Ghana found that this tree relies heavily on the straw-coloured fruit bat (Eidolon helvum) for seed dispersal, over 98% of the seed falling to the ground having passed through its gut. This seed also germinated better than uneaten seed and resisted predation longer.