Key Terms
§ Keystone species : A keystone species is a species that has a disproportionate effect on its environment relative to its biomass. The elephant, woodpecker, black rhinoceros, and African wild dog are keystone species because of the large impact they have on the savanna. For example, without predators like the African wild dog, the populations of their prey would expand out of control, which would have a domino effect on many aspects of the savanna ecosystem.
§ Endangered species: A species whose numbers are so small that the species is at risk of extinction. The African wild ass, black rhinoceros, ethiopian wolf, and striped hyena are all endangered species because their numbers have declined so drastically.
§ Endemic (native) species: Endemism is the ecological state of being unique to a particular geographic location, such as a specific island, habitat type, or nation. The lion, common waterbuck, giraffe, and zebra are all endemic species because they naturally evolved on the savanna.
§ Invasive (non-native) species live outside their normal distribution area and threaten biological diversity. Many were introduced on purpose, either for commercial or ecological reasons. However, they end up causing damage to the biodiversity. Some well-known invasive shrubs are Lantana camara and Duranta erecta. Some of the worst invasive species or grass in South American and Australian savannas are Melinis minutiflora and Andropogon gayanus, which are native to Africa, but not South America or Australia. The fire ant is another invasive species in the savanna that is decimating the native ant population.
§ Threatened species are any species (including animals, plants, fungi, etc.) which are vulnerable to endangerment in the near future. The cheetah, African hunting dog, African hunting dog, and wattled crane are considered threatened species because their numbers have declined dramatically, but not low enough to be considered endangered.
§ Generalist species: A generalist species is able to thrive in a wide variety of environmental conditions and can make use of a variety of different resources. Because of their versatility, the African savanna hare, emu, black mamba snake, and lion are considered generalist species .
§ Specialist species can only thrive in a narrow range of environmental conditions or has a limited diet. For example, the koala bear has a very limited diet of eucalyptus leaves, the palm-nut vulture mainly eats fruit from the oil palm, and the aardwold mainly eats termites. Four species of stinging ants, Crematogaster nigriceps, Crematogaster mimosae, Crematogaster sjostedti, and Tetraponera penzigi, have adapted specifically to the whistling thorn acacia in Kenya. The thorns and the "nectary" glands of the whistling thorn acacia are necessary for their nests, so these species of ants are only found in this type of acacia Because of the narrow range of their habitat, these ants are specialist species.
§ Foundation species: A foundation species is a dominant primary producer in an ecosystem both in terms of abundance and influence. By definition, a savanna is a grassy plain dotted with trees. Therefore it is not surprising that grasses are the main foundation species of the savanna. Trees such as as the acacia tree, river bush willow, jackalberry tree (which earned its name because jackals love to eat its fruit), and baobob tree are also foundation species. Both the grasses and trees are foundations species because they serve as food for the vast number of herbivores and omnivores of the savanna.
§ Indicator species: An indicator species is any biological species that defines a trait or characteristic of the environment. Birds are common indicator species. Like the canary in the coalmines, birds in the savanna are indicators of air quality because of their delicate respiratory systems. Birds may be the first animals to be affected by changes in the environment, but whatever causes a decrease in their populations will usually affect the other species too. Some examples of birds that act as indicators species in the savanna are the lilac breasted roller bird (shown below), white-browed sparrow weaver, Superb Starling, and northern pied-babbler. Bats are also indicator species in the savanna.