Geography and distribution
Restricted to Madagascar (Toliara Province), where it is only known to occur in a small area north of Morondava, which includes the small, private reserve of Kirindi (Kirindy) Forest. It has been found at 20–500 m above sea level.
Overview: A deciduous shrub or tree, with prickles, growing up to 5 m tall. The mature stem is smooth and grey-brown, and the twigs are pale grey, with numerous tough prickles up to 5 mm long.
Leaves: The leaves are feather-like, yellowish and hairy, with a stalk (main axis) with curved prickles underneath and a gland near the petiole base. There are up to 30 pairs of segments, which are whitish and hairy, and numerous leaflets (about 17–40 pairs per segment), which are up to 2.5 mm long on mature stems.
Flowers: The bottle-brush-shaped inflorescences are axillary, about 1.5–4.0 cm long and elongate towards the tip of new growths. The flowers are more or less densely spaced, about 4–5 mm long (including the stamens) and scented. The calyx and corolla are green, and the numerous stamens are pale greenish cream. The anthers are cream.
Fruits: The seed pods are oblong, slightly curved, flattened (but raised at the margin and over each seed), 8.0–10.0 cm long, 1.2–1.5 cm wide and straw-coloured. The seeds are discoid or elliptic in outline, 6–7 mm long and 5–7 mm wide, with a horse-shoe shape-like line surrounding the areole (pleurogram).
The story behind the name
The type specimen (holotype) of Acacia menabeensis, which is held in the Paris Herbarium (Herbier National de Paris), was originally described as Acacia minutifolia in 1879 by French botanist Emmanuel Drake. However, this name is illegitimate as there is another A. minutifolia described by Ferdinand von Mueller in 1874. Upon realising this, botanists Jean-Francois Villiers and David Du Puy had to give a new name to the species, which then became A. menabeensis, as published in The Leguminosae of Madagascar.
Two duplicates (isotypes) of the type specimen are held in Kew’s Herbarium.
Threats and conservation
No population data are available for Acacia menabeensis, which is thought to be very restricted in its distribution (and which is known from only six herbarium collections). The major threat to Madagascar succulent woodland is fire, both as a result of wildfires and intentional burning for expansion of agricultural land. There are no known conservation measures specifically for A. menabeensis, and it is known to occur in only one protected area, the Kirindy Mite National Park. It has been recommended that seeds of A. menabeensis are collected and stored as an ex situ conservation measure.
Due to its restricted Extent of Occurrence (which is less than 100 km²) and estimated Area of Occupancy, the lack of precise information on its population dynamics, and the high level of threat to its dry deciduous forest and succulent woodland habitats, A. menabeensis is currently rated as Critically Endangered. Further research and fieldwork are required to better understand the distribution, health and population dynamics of A. menabeensis.
Conservation assessments carried out by Kew
Acacia menabeensis is being monitored as part of the IUCN Sampled Red List Index for Plants, which aims to produce conservation assessments for a representative sample of the world’s plant species. This information will then be used to monitor trends in extinction risk and help focus conservation efforts where they are needed most.
Millennium Seed Bank: Seed storage
The Millennium Seed Bank partnership aims to save plant life worldwide, focusing on plants under threat and those of most use in the future. Seeds are dried, packaged and stored at a sub-zero temperature in Kew's seed bank vault at Wakehurst.
Description of seeds: Seeds with hard coat, discoid or elliptic in outline, 6–7 mm long, 5–7 mm wide, with a pleurogram.
Number of seed collections stored in the Millennium Seed Bank: None.
Seed storage behaviour: Orthodox (the seeds of this plant survive drying without significant reduction in their viability, and are therefore amenable to long-term frozen storage such as at the MSB).
This species at Kew
Pressed and dried specimens of Acacia menabeensis are held in Kew’s Herbarium, where they are available to researchers from around the world, by appointment. The details of some of these specimens can be seen online in the Herbarium Catalogue.