**2. Ecological significance**

**Morphological variation [1, 13] Current taxonomic status** 

**Figure 3.** A young *Vachellia karroo* tree, splendidly armoured with long white thorns (photo: M. Dingaan).

3. Fire resistant shrubs in the Nongoma District, KwaZulu-Natal Formerly *A. inconflagrabilis*,

7. Small shrubby form on the Springbok flats north of Pretoria Still *V. karroo*, closely

1. White-barked trees or shrubs with short spines, found in Eastern Cape, KwaZulu-Natal, Mpumalanga and neighbouring countries (Swaziland, Zimbabwe and

4. Slender sparsely branched trees in the Hluhluwe and Umfolozi Game Reserves,

5. Large trees with greyish-white bark along the Tugela River mouth (KwaZulu-

from Pretoria eastwards (for example Sekhukhuneland, Limpopo)

6. Sparse indumentum on young shoots, leaves peduncles and pods on the Highveld

2. Small slender shrubs found near the Kei River mouth, Eastern Cape *V. dyeri*

Mozambique)

114 Pure and Applied Biogeography

KwaZulu-Natal

Natal), and northwards into Mozambique

**Table 2.** The *Vachellia karroo* complex.

**[5, 16]**

*V. natalitia*

still a synonym

*V. kosiensis*

*V. robbertsei*

*V. theronii* (or *V. montana*)

resembles *V. tenuispina*

This is an ecologically and socio-economically important species described by many as a multi-purpose tree and an asset to any farm [18].

#### **2.1. Value as fodder and food supplement**

*Vachellia karroo* attracts many insects and therefore birds, and its flowers also form an important food supplement for animals [1]. The flowers have significant amounts of pollen and are rich in protein and are thus eaten by birds such as Grey Go-Away birds (also known as Grey Louries) and monkeys [5]. In addition, the larvae of several butterfly species feed on the pods and flowers [5, 16]. Its flowers also provide nectar for bees and are important for the production of honey [1]. *V. karroo* trees are important for bee farming as they indirectly result in the production of a pleasantly flavoured honey [6].

Furthermore, parts of *V. karroo* are used as food for humans, as an example, seeds are roasted and used as coffee substitute [19]. *Vachellia* species can produce large amounts of seeds which are known to have been eaten by pastoral people when the need arose, and indirect food sources include the edible cerambycidae wood borer larvae found in the dead wood of *V. robusta* [1].

Despite its thorniness, *V. karroo* is a good fodder tree and forms an important part of the diet of a wide range of herbivore species [2]. It is palatable [20] and consumed by both domestic and wild species [21]. Its foliage is highly favoured by stock and game, so are its seeds and dehiscent pods, which are rich in protein [18]. The pods and seeds also play an important role as feed supplements during the dry season [22] as they are at times collected by farmers to feed their livestock [1]. *V. karroo* has been shown to be an important part of the giraffe diet [23], and it has also been observed that goats select *V. karroo* in preference to grass, but less so, when the amount of available browse available is limited [21]. The foliage, pods, and flowers of *V. karroo* are free of hydrocyanic poisoning, a self-protection mechanism used by many trees [6], relating to the toxic substance known as hydrocyanic acid, prussic acid, or cyanide. Some *Vachellia* species pose the danger of such poisoning to animals. These include *V. erioloba*, whose pods and young leaves contain prussic acid, as well as the wilted leaves of *V. sieberiana* [1].
