Adansonia grandidieri
Adansonia grandidieri is the biggest and most famous of Madagascar's six species of baobabs. It is sometimes known as Grandidier's baobab or the giant baobab. In French it is called Baobab malgache. The local name is renala or reniala. This tree is endemic to the island of Madagascar, where it is an endangered species threatened by the encroachment of agricultural land. This is the tree found at the Avenue of the Baobabs.
Description
Grandidier's baobabs have massive, cylindrical, thick trunks, up to three meters across, covered with smooth, reddish-grey bark. They can reach in height. The crown is flat-topped, with horizontal main branches.Leaves
Leaves are palmately compound, typically with 9 to 11 leaflets. This is the only species of baobab with leaflets that are blueish-green and that are densely covered with star-shaped hairs.Flowers
Flowering occurs during the dry season, from May to August, before leaves appear. Buds are erect, rounded and dark brown. The flowers are made up of 5 calyx lobes that are bent back and twisted at the base of the flower. The lobes are fused at the base forming an open cup about 1 cm deep. Petals are white, aging to yellow, up to 20 mm long and about 5 times as long as broad. The flowers have a white central tube that is up to 16 mm long and is made up of fused stalks of stamens. 600 – 700 unfused filaments up to 6.5 cm long spread out from the top of the staminal tube. A densely hairy ovary is enclosed in the staminal tube, and a long style tipped with a white or pinkish stigma emerges from the filaments.Fruits and seeds
The fruits are large, dry and rounded to ovoid. They have a hard shell 2 – 4.5 mm thick and are covered with dense reddish-brown hairs. They contain large kidney-shaped seeds within an edible pulp.Range and habitat
This baobab occurs in south-western Madagascar, between Lake Ihotry and Bereboka. Grandidier's baobab used to inhabit dry, deciduous forest, especially near seasonal rivers or lakes. However, today it is mainly found in open, agricultural land or degraded scrubland.Life cycle and ecology
The long-lived Grandidier's baobab is in leaf from October to May, and flowers between May and August. The flowers, said to smell of sour watermelon, open just before or soon after dusk, and all the pollen is released during the first night. The tree is pollinated by nocturnal mammals, such as fork-marked lemurs, and insects like the Hawk Moth. The lemurs move through the canopies, inserting their snouts into the white flowers and licking nectar from the petal bases, resulting in pollen being deposited on the lemurs' faces, whereas the moth is slightly more effective at pollination because it flies from tree to tree with most of its body covered in pollen.The species bears ripe fruit in November and December. Unlike the baobabs of Africa and Australia, it appears that the seeds of the tasty fruit are not dispersed by animals. Lemurs are the only living animals on Madagascar that are capable of acting as seed dispersers, yet seed dispersal by lemurs has never been documented. In the past, however, this could have been very different. Several species have gone extinct since human colonization of the island that could very likely have been dispersers of the seeds. This includes species of primates that were thought to be similar to baboons, and the heaviest bird that ever lived, the elephant bird, which had a powerful beak that could have opened large fruit. Today, water may be the means by which the seeds are dispersed.
Lack of water can sometimes be a problem for plants in Madagascar. It appears that the baobab overcomes this by storing water within the fibrous wood of the trunk, as the tree's diameter fluctuates with rainfall.
Taxonomy
Adansonia grandidieri was first described and published by botanist Henri Ernest Baillon in A.Grandidier's, Hist. Phys. Madagascar: tables 79e and 79a in 1888. The genus Adansonia honours the French explorer and botanist, Michel Adanson. The species name grandidieri honours the French botanist and explorer Alfred Grandidier.All species of Adansonia except A. digitata are diploid.
The genus Adansonia is in the subfamily Bombacoideae, within the family Malvaceae in the order Malvales. Adansonia grandidieri is classified in section Brevitubae with the close relative Adansonia suarezensis. These are baobabs that are large trees with ovoid flower buds set on short, erect stalks.