DIVERSITY & ENDEMISM
For an arid region, the Succulent Karoo has extraordinarily high plant endemism, including the richest succulent flora in the world. In total, there are more than 6,350 vascular plant species in this hotspot, nearly 2,440 of which are endemic (40 percent). Local plant species richness is very high, with an average of 70 species found in 0.1 hectare test plots, and the diversity between sites in the region is also significant. Many plants in the Succulent Karoo, especially succulents, are specialists for a limited range of environmental conditions, producing a phenomenon known as point endemism. Regional endemism is notable at the genus level; 80 genera are found nowhere else in the world.
Notable plant species found in this hotspot include the botterboom (Tylecodon paniculatus), a stem succulent that has glossy leaves in winter and red flowers in summer, and the halfmens ("half human") (Pachypodium namaquanum), a stem succulent endemic to the Richtersveld that can grow up to four meters tall. Clusters of halfmens stems tend to face toward the north, giving the appearance of groups of people gazing northwards. The stems' crowns of leaves, which resemble hairy human heads, enhance the impression. The scientific explanation for this unusual orientation is that the plants, which grow on shaded slopes, lean northwards in order to ensure that their leaves and developing flowerheads, produced during the cool, foggy winter months, are maximally exposed to the sun's warming rays.
The avifauna of the Succulent Karoo includes more than 225 species, one of which is endemic: Barlow's lark (Certhilauda barlowi). Other species in the region include the black harrier (Circus maurus, VU), which has the most restricted range of the world's 13 harrier species, Karoo bustard (Eupodotis vigorsii), Ludwig's bustard (Neotis ludwigii), Karoo chat (Cercomela schlegelii), dune lark (Certhilauda erythrochlamys), and dusky sunbird (Nectarinia fusca).
There are roughly 75 mammal species in the Succulent Karoo hotspot, of which two are endemic: De Winton's golden mole ( Cryptochloris wintoni, VU), and the Namaqua dune mole rat (Bathyergus janetta). An important flagship species in the region is the riverine rabbit (Bunolagus monticularis, CR), found in the Succulent Karoo, and whose population is thought to have declined by 60 percent over the past 70 years such that no more than perhaps 250 individual remain.
Major concentrations of large mammals, including elephant (Loxodonta Africana, VU), black rhinoceros (Diceros bicornis, CR), and African buffalo (Syncerus caffer), once roamed the gallery forests along the Orange River in the Succulent Karoo. These populations have now disappeared from the hotspot. Today, only smaller herds of gemsbok (Oryx gazella), mountain zebra (Equus zebra), and springbok (Antidorcas marsupialis) can still be seen there.
Reptile diversity is relatively high in the Succulent Karoo, with more than 90 species, about 15 of which are endemic. All of the endemics are geckos and lizards, representing about a quarter of the nearly 60 gecko and lizard species in the hotspot. These endemics include seven species of girdled lizards of the genus Cordylus, including the armadillo girdled lizard (Cordylus cataphractus, VU). This lizard has a heavily armored body and spiny tail and is known for rolling into a tight ball when threatened.
As in the rest of South Africa, tortoise diversity is very high in the Succulent Karoo, with seven taxa, two of which are endemic: the Namaqualand tent tortoise (Psammobates tentorius trimeni) and the Namaqualand speckled padloper (Homopus signatus signatus).
Amphibians are poorly represented in the Succulent Karoo with just over 20 species. All of these species are frogs, including one endemic, the desert rain frog (Breviceps macrops, VU), which occurs along the Namaqualand coast of South Africa north to Luderitz in coastal southwestern Namibia.
There are about 26 species of freshwater fish in the Succulent Karoo, none of which are endemic.
Invertebrate diversity is quite high in the Succulent Karoo, and evidence suggests that more than half of the species in some insect groups are endemic. Of the 70 species of scorpions found in the hotspot, nearly 20 are endemic. Monkey beetles, which are almost exclusively found in southern Africa, are concentrated in the area. Along with many types of wasps and bees, these beetles pollinate the hotspot's diverse plant species. Perhaps the most unusual invertebrates found here are the long-tongued flies (Memestrinidae), which can have mouthparts up to 50 millimeters long. The flies are the exclusive pollinators of 28 different plant species in Namaqualand.