Included here is the Island of Madagascar in the Indian Ocean.

Southern and Southwestern Madagascan Spiny Forest-Scrub

In dry southern and southwestern Madagascar these so-called spiny forests are probably more accurately described as thorn-scrub since they normally grows to no more than about 6 m tall, but often include a scattering of emergent trees growing to about 10 m high. Otherwise there is no stratification and many stands are virtually impenetrable. The most distinctive elements are members of the near endemic family Didiereaceae and arborescent species of Euphorbia. The family includes four genera and twelve species - Didierea (D. madagascariensis and D. trollii), Alluaudia (six species), Alluaudiopsis (two species) and the montypic genus Decaryia (D. madagascariensis).  Alluaudia ascendens and A. procera reach heights of 8m but most others are smaller than this. Of the Euphorbia species many are endemic and include several that have caducous leaves and green fleshy stems. One of the most abundant of these is the spiny endemic Euphorbia stenoclada (Euphorbiaceae), which can grow to a height of 10 m or more. The emergent trees include a few island endemics such as Adansonia fony, A. za (Malvaceae), Dicoma incana, D. carbonaria (Asteraceae) and Tetrapterocarpon geayi (Fabaceae). These forests are very rich in species but species composition varies greatly from place to place. Important woody plants often include the endemic or near endemics genera Megistostegium (Malvaceae) and Uncarina (Rubiaceae), the endemic species Rhigozum madagascariensis (Bignoniaceae), together with many endemic species of Acacia, Commiphora, Dichrostachys, Iphione, Cadaba, Sclerocarya, and the endemic palm Dypsis decaryi (Arecaceae). As expected, many of the taxa, such as Allaudia, Didierea, Mimosa and Pachypodium, have abundant spines. Lianas are numerous but rather small and include several endemic members of the Asclepiadaceae. Examples include species of Adenia, leafless species of Cissus, and species of the endemic genus Xerosicyos (Cucurbitaceae) with their thick fleshy leaves.  The ground flora is usually sparse but may include tufts of the endemic grass Humbertochloa bambusiuscula (Poaceae) together with endemic succulent species of Aloe (such as the rare Aloe suzannae), Euphorbia, Senecio and Notonia.


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