Alluaudia is a genus of six species of flowering plants in the family Didiereaceae, within the order Caryophyllales. All six species are endemic to Madagascar, where they are characteristic of the southwestern subarid forest-thicket vegetation — a region often called the spiny forest or spiny thicket, one of the most distinctive and biodiverse dryland habitats on the island.
Plants in the genus are spiny, columnar or branching succulents that can reach considerable heights. They are dioecious, meaning male and female flowers are borne on separate individuals. The spines are arranged around the small leaves and are positioned several meters above the ground; this unusual placement is thought to reflect an evolutionary response to browsing by now-extinct large lemurs, such as Hadropithecus, that once inhabited Madagascar. Despite the defensive spination, several extant lemur species rely heavily on Alluaudia as a food source, including the ring-tailed lemur (Lemur catta) and the white-footed sportive lemur (Lepilemur leucopus).
The genus belongs to Didiereaceae, a plant family almost entirely restricted to Madagascar and closely related to cacti and other stem-succulent families of the order Caryophyllales. Alluaudia is one of the most recognizable genera in Madagascar's spiny forest, with species such as Alluaudia procera forming the towering, spine-studded columns that define the landscape of the island's arid south.
Distribution
All six species of Alluaudia are endemic to Madagascar. Most occur in the southwestern subarid forest-thicket vegetation — the island's iconic spiny forest — which stretches along the arid southwestern coast.
Ecology
Alluaudia species play a key role in the ecology of Madagascar's spiny forest. Their spines are positioned several meters above ground, likely as an evolutionary defense against now-extinct large lemurs such as Hadropithecus. Today, living lemurs including the ring-tailed lemur (Lemur catta) and the white-footed sportive lemur (Lepilemur leucopus) depend heavily on Alluaudia as a food source.
Taxonomy Notes
Alluaudia belongs to the family Didiereaceae, order Caryophyllales — a family of spiny succulent plants nearly endemic to Madagascar and closely allied to the cactus lineage. GBIF recognizes five accepted species within the genus; the Wikipedia article lists six species as endemic to Madagascar.
