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Introduction to Southern Africa’s Reptile Fauna
by Bill Branch
Port Elizabeth Museum, Bay World, Port Elizabeth
Southern Africa has the richest reptile diversity in Africa, with a fauna that currently comprises 498 species (578 taxa if one includes subspecies) in 116 genera and 23 families. Present rates of discovery, which for lizards are still comparable to those in the early phase of exploration in the 19th century, indicate that the reptile fauna may approach, if not exceed, 600 species when fully documented. The diversity of the reptile fauna approaches that of resident, breeding birds (approximately 680 species). Only two reptiles (a small snake, Rhamphotyphlops braminus and a terrapin Trachemys scripta) are introduced into South Africa, and both have limited distributions with little evidence of range expansion.
Lizards form the dominant component of this rich fauna (299 species, 60.9% of the total), due, in part, to an exceptional radiation of geckos in the western arid regions, and of cordylids in the escarpment mountains. With the exception of the Anguidae, which has a limited penetration into extreme North Africa, all other eight lizard families that occur in Africa have representatives in the subcontinent. Within lizards, the families Gekkonidae, Scincidae and Cordylidae are particularly well represented. Geckos dominate (91 species, 30.4% of lizard fauna), followed by skinks (69 species, 23.1%), cordylids (55 species, 18.4%) and lacertids (37 species, 12.4%).
Snakes are the next most speciose group (146 species, 29.7%), followed by chelonians (turtles, terrapins and tortoises; 28 species, 5.7%) and amphisbaenians (worm lizards; 18 species, 3.6%). There is also a single crocodilian (the Nile Crocodile; 0.2%).
The amphisbaenian diversity is the richest in Africa, with 12 species recorded from Zimbabwe and nine from both South Africa and Botswana. Despite their relatively low numbers, land tortoise (Testudinidae) diversity within the region is significant, comprising 14 of the world’s 42 living species (33.3%) and 5 of the 11 genera (45.5%).
The current rate of species description shows little indication of reaching a plateau, even after 250 years of scientific study. This is evident in the increase in number of species listed for the region after a 10-year period: 397 species in 1988 and 480 species in 1998. Moreover, the descriptions of nearly a dozen species await publication, and it is expected that many more will be discovered. It is evident that the reptile diversity of the subcontinent remains poorly documented.
The richness of southern Africa’s herpetofauna is best illustrated in comparison to the Congo, the second largest country in Africa and almost equal in size to the southern African subcontinent. The Congo has a rich herpetofauna (amphibians and reptiles) of 522 species. However, only 290 of these are reptiles, and only 95 are lizards. In contrast, southern Africa is likely to have a greater number of gecko species (probably in excess of 100 species) than the total lizard fauna of the Congo. Within the subcontinent, South Africa has the richest diversity of reptiles and, after the continental herpetofauna of Australia (a much larger area) and Mexico, it has the third richest lizard fauna in the world.
In addition to its diversity, the southern African reptile fauna has a high level of endemism. In other words, many of the species found in the subcontinent are found nowhere else on earth. Of nearly 500 species recognised from the subcontinent, 391 are endemic (78.5%) to it. Among frogs and freshwater fish, endemism in the subcontinent ranges from 50-60%, while in birds and mammals it is less than 25%.
Endemism in all lizard families, with the exception of the wide-ranging varanids, is high (mean 65.3%), especially within the families Cordylidae (85.5%) and Chamaeleonidae (95%). This high level of endemism is a consequence of the restricted distributions of many species, and this has important conservation implications for these species.
[ last updated on 5-May-2005 ]
|September 20, 2017, 11:38 pm|