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Acacia drepanolobium

Vachellia drepanolobium
Whistling thorn.jpg
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Rosids
Order: Fabales
Family: Fabaceae
Genus: Vachellia
Species: V. drepanolobium
Binomial name
Vachellia (Acacia) drepanolobium
(Harms ex Sjöstedt) P.J.H.Hurter
Acacia-drepanolobium-range-map.png
Synonyms
  • Acacia drepanolobium Harms ex Sjöstedt

Vachellia drepanolobium (syn. Acacia drepanolobium), commonly known as whistling thorn (family Fabaceae), is a swollen-thorn vachellia native to East Africa. The whistling thorn grows up to 6 meters tall. It produces a pair of straight thorns at each node, some of which have large bulbous bases. These swollen thorns are naturally hollow and occupied by any one of several symbiotic ant species. The common name of the plant is derived from the observation that when wind blows over bulbous thorns in which ants have made entry/exit holes, they create a whistling noise.

Whistling thorn is the dominant tree in some areas of upland East Africa, sometimes forming a nearly monoculture woodland, especially on "black cotton" soils of impeded drainage with high clay content. It is browsed upon by giraffes and other large herbivores. It is apparently fire-adapted, coppicing readily after "top kill" by fire.

Whistling thorn is used as fencing, tool handles, and other implements. The wood of the whistling thorn, although usually small in diameter, is hard and resistant to termites. The branches can also be used for kindling, and its gum is sometimes collected and used as glue. The ability to coppice after cutting make it a possibly sustainable source for fuel wood and charcoal. Conversely, whistling thorn also has been considered a weed of rangelands, and a bush encroachment species.

Like other acacias, whistling thorns have leaves that contain tannins, which are thought to serve as deterrents to herbivory. Like all African acacias, they are defended by spines. In addition, Whistling thorn acacias are myrmecophytes that have formed a mutualistic relationship with some species of ants. In exchange for shelter in the bulbous thorns (domatia) and nectar secretions, these ants appear to defend the tree against herbivores, such as elephants and giraffes, as well as herbivorous insects.

At one site in Kenya, four ant species compete for exclusive possession of individual whistling thorn trees: Crematogaster mimosae, C. sjostedti, C. nigriceps, and Tetraponera penzigi. Ants vary in their level of mutualism with whistling thorn trees. The most common ant symbiote (~ 50% of trees), C. mimosae, has the strongest mutualistic relationship, aggressively defending trees from herbivores while relying heavily on swollen-thorns for shelter and feeding from nectar produced by glands near the base of leaves. (see also Crematogaster peringueyi)


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Wikipedia

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