££AI'J D.R.F.N. :Rffi\!'ll _ REF ERE NCE:'h'iL _ LIBRARY :",,'-tlK INSECTS OF THE SPERRGEBIET KARAS REGION, NAMIBIA COMPILED BY ; Eugene Marais 1493 Namibian National Insect collection State Museum of Namibia P.O. Box 1203 Windhoek EXUCUTlVE SUMMARY From an ecological perspective, the Sperrgebiet is difficult too classify. Although usually regarded as situated in the Namib Desert biorne, it is really atrnasition~l area between the mild arid Succulent Karoo biome, the hyperarid Namib Desert biome, and the hot arid Narna Karoo biome. The situation is further complicated by a number of faunal provinces bordering on the area, as well as the unique character of its own fauna. Quantified extrapolation of data on the insect fauna of the area are almost impossible, as no systematic entomological investigation of the area has been attempted, and as the insect material collected from the area are mainly unpublished, unidentified and scattered in a number of insti tutions and countries. However, the pUblished information on ~ southern Africa were perused, and relevant information has been extracted from a number of sources. These sources indicated that: 1. The insect groups of primary ecological significance are those genera, tribes, subfamilies, and families which have reach their highest diversity in southern Africa in the African South West Arid biogeographical region (ASWA). 2. Those insect groups with a large number of endemic species in the ASWA, usually have a number of species endemic to the Sperrgebiet or its immediate vicinity. 3. Insect groups of a predominant herbivorous biology and highest diversity in the ASWA, usually have an unusual number of species endemic to the Sperrgebiet. 4. Published distribution records, especially based on old collection records, should be regarded with reservations, as the localities are often misleading or inaccurate. 5. Information about the fauna of the littoral zone, the coastal area, and the Orange River mouth area are virtually non-existent. Despite this lack of information, I still regard these areas as some of the most ecologically sensitive areas, especially in view that these areas are most severely affected by the mining activity and resultant settlement. The fauna from these areas will also constitute the principal agents for recolonizing prospective 2 rehabilitated mining areas, and a proper investigation into these faunal communities should have been available already. 6. The most reliable information on the insect fauna of specific ecotypes are from the Obib/Oaberas area, from Rosh Pinah, and from the Klinghardt mountains. 7. The Klinghardt mountains and Skilpadberg (close to Hohenfels) have resident populations of some very restricted species, while the area from the Orange river mouth to about 15 Jan upstream is suspected to harbour similar popUlations of unique freshwater species. These areas (Klinghardtsberg, Skilpadberg, and the lowermost Orange river) should be regarded as core conservation areas, access to them should be stricktly controlled, and further degradation of the habitat by human activity should be prevented. Other areas in the Sperrgebiet display similar unique populations of insects, but are much more resilient due to the large area of available habitat. In general the study was severely restricted by the lack of comprehensive information on the Sperrgebiet insects, but this problem is typical for almost the whole of Namibia. However, information insects from the area was extraordinary difficult to obtain. This can partially be explained by the remoteness and inaccessibilty of the area, but the major reason is the severe restrictions imposed by various authorities since diamonds was discovered there. I am of the opinion that some of the profits from the diamond mining activity should be used to rectify the present dearth of information as quickly as possible, especially in the light of the potential importance of the C2) area as a unique refuge of genetic material. A primary goal of such an effort should be to retain the material and information in Namibia, and not to let it be exported as in the past. It is furthermore recommended that the area should be provided with protective legislation as soon as possible, with the aim to safeguard its genetic resources while it still contain a neg legible human popUlation and a single industry. In addition, a coherent programme should be launched to collect additional data, with the additional goal to identify and safeguard core conservation areas within a larger buffer area. 3 BACKGROUND The Sperrgebiet is generally regarded as part of the Namib Desert biome. However, it is the transitional area between the succulent Karoo biome to the south and the Namib Desert biome to the north, as well as the transition between the Nama Karoo biome to the east, the Marine biome to west, and the Namib Desert and Succulent Karoo biomes in the middle. In addition, the northern part of the Sperrgebiet represents the transition between the hyperarid, vegetationless, unconsolidated dunes of the Central Namib and the moving barchans and undulating vegetated sands od the Southern Namib. However, the first mobile major dunes of the Namib desrt occur in the far southeast of the Sperrgebiet. These dunefields of the Sperrgebiet is known be the genetic epicenter of the majority of the present fauna of the Namib biome. In the south, the Richterveld/Huns mountains, with their known high levels of unique endemic species, intrude into the Sperrgebiet in the Rosh pinah/Daberas/Obib area. The southern border itself is the lowermost part of the Orange/Vaal riverine system, known for its distinct complex of freshwater species. In addition, the evolutionary extremes of the genetic lineages typical of the reknown Cape biogeographical province can be found in the Sperrgebiet. The Sperrgebiet therefore harbours a Rn~~~~ial. It is a true meeting place of the insect fauna of the east and the west, of the north and the south. Although the entomological resources of the area have been poorly studied, their is abundant evidence from a number of unexpected groups to support this hypothesis. The Namib biome as a whole, including the Sperrgebiet, are usually classified into three major habitat types or biotopes - dunefields, gravel plains and riverbeds. These divisions are not simply made on the basis of predominant substrate or geomorphological features, nor are they made to simplify habitat recognition. These biotopes have distinct faunal assemblages, and "indicator" species for these desert habitat types are usually insects, especially the highly visible 4 tenebrionid or darkling beetles. The individual biotopes themselves are subdivided into smaller distinct habitat types within a specific biotope; either based on habitat preferences of faunal elements within the assemblages, e.g. hummock dunes, interdune plains, mobile dunes; riparian vegetation, reedbeds, trees; etc; or into less distinctly defined habitat units (ecotypes) based on subassemblages of faunal elements and climatic, substrate or vegetation characteristics, e. g. coastal dunes, inland dunes, peripheral dune areas; or southern (including the Sperrgebiet), central, and northern Namib. Distibutions are temporally flutd, over longer or shorter periods due to changes in environmental conditions, and species usually associated with a different ecotype or even biotope can therefore occur in adjacent areas under favourable conditions. However, core areas within the range of various species can usually be identified, from which habitat classifications can be discerned based on typical faunal subassemblages. Expected faunal subassemblages are therefore important when specific habitats and areas are investigated. other smaller distinct habitat types, which are not always associated with a single one of the common biotopes mentioned above, can also be recognized, e. g. the littoral zone, lichen fields, temporal grass fields, etc. Each of these habitat types will again have their own typical faunal subassemblages . ..', In the southern Namib another biotope of critical importance occur, the :;.- isolated inselbergs and mountain ranges. Similar extensive outcrops of elevated bedrock are rare in the central and northern Namib, and where they occur they are usually .s!.evoidof distinct fauna due to (!) palaeohistorical reasons. The major concern when investigating such habitat types should be to tpentify those of limited geographical size and distinct faunal guilds. These habitat types should be the primary concern when selecting areas for conservation, as they will not have the recuperational resilience of larger areas, and their degradation are usually accompanied by a 5 loss of genetic material unrelated to the size of the area. However, due to the dearth of systematic information for most of the remote areas of Namibia, such habitats can presently only be defined by combining information on the occurrence of geographically limited species with an intelligent assessment of the evolutionary history and physical attributes of a specific area, as well as the habitat preference and biological necessities of the species in question. The role of the Sperrgebiet in the evolutionary history of most of the endemic fauna of the African South West Arid Region of Africa, either because endemic species which radiated from evolutionary centers elsewhere in the region occur only there, or because it served as an evolutionary center for specific groups, are an important consideration in this regard. various studies have