African Journals Online
African Entomology

Volume 10, Issue 1, March 2002

Insect conservation in South Africa : an overview
McGeoch, M.A. 1-10

Abstract: Although insects have a long tradition of use and appreciation in South Africa, insect conservation in the country dates back to 1976 with the first formal protection of a group of butterfly species. Today South Africa has a strong insect conservation research record, with significant contributions from both professional and amateur entomologists. This activity has in a number of instances led to insect conservation management actions. As in many other parts of the world, threats to arthropod diversity include rapid rates of land transformation in the form of, for example, overgrazing, soil erosion, urbanization, deforestation, the expansion of exotic plantations and invasive species. The impact of exotic and invasive flora is of particular concern in rare and restricted habitat types, such as high-altitude montane grassland. Initiatives aimed at promoting the cause, and improving the status, of insect conservation in South Africa include the identification of bioindicators, ecological landscaping, the conservation of insects in urban environments, as well as the mapping of species distributions to include insects in procedures for the identification of priority areas for conservation. Species that are extensively used as primary resources, such as mopane worms and wild silk moths, pose particular challenges to insect conservation in South Africa. In addition to long-term socioeconomic stability, the future of insect conservation in South Africa lies in national coordination of research and implementation initiatives, as well as continued financial support and the prioritization of conservation and research activities in the country.

Insects and the determination of priority areas for biodiversity conservation in KwaZulu-Natal province, South Africa
Armstrong, A.J. 10-27

Abstract: The KwaZulu-Natal Nature Conservation Service is undertaking a long-term project to determine the value of untransformed land for biodiversity conservation, to mapthese areas in accordance with their relative values, and to identify and prioritize irreplaceable areas. The overall goal of the initial stage of the project was to use existing data and expertise to define areas of conservation importance in KwaZulu-Natal. The aim of this paper is to illustrate the procedures used to incorporate insect species and subspecies into the project, including those for identifying insects of conservation concern and for making a first assessment of their distribution and conservation status. A biodiversity hierarchy (from landscapes through ecosystems and communities to species and populations) forms the basis of the analysis. Information received from taxonomists working in South Africa in response to a questionnaire survey was used to choose the species for inclusion in the initial analysis. A total of thirty-seven species and subspecies endemic to the Province in certain families of Coleoptera, Diptera, Lepidoptera, Mecoptera and Odonata were included. Existing distribution data were collated and the potential distributions of the endemics were modelled at a scale of 4 ha. Factors that potentially influence the distributions of the endemics were gleaned from the literature. Database queries using distribution data with a spatial resolution of <250 m and cartographic overlays formed the basis of the modelling procedure. Two areas with little or no statutory protection, the high-lying grasslands of the northwestern region and much of the central region of the Province, are predicted to have a relatively high diversity of endemic insects. Fifty-one percent of the insect species and subspecies in the analysis met the two conservation goals, i.e. 1) at least 10 % of their present distributions under formal conservation management, and 2) three such protected areas with viable populations. A benefit of modelling the potential distributions of endemics is that searching for populations of these insects can be directed to areas where they are expected to occur. The data collected can then be used to improve the distribution models for these insects, some of which are poorly known. The distributions and their associated conservation targets format vital component of the iterative systematic conservation planning project currently underway in the Province.

Conservation application of existing data for South African millipedes (Diplopoda)
Hamer, M.L.Slotow, R.H. 29-42

Abstract: While there are currently several initiatives to identify priority areas for conservation, invertebrates, which may comprise as much as 95 % of biodiversity, are generally excluded from such activities. It is assumed that vegetation types and patterns of floral diversity will adequately reflect those of the underlying diversity, i.e. invertebrates. A lack of adequate data and expertise are the main contributing factors to the exclusion of invertebrates. Existing data for South African millipedes were evaluated in terms of usefulness for biodiversity conservation planning and management. We used databases from several museums and published records. Large gaps exist in the collecting coverage of South Africa, and many records date back to the early part of the last century. Quarter-degree grid cells containing the highest species richness, and the highest number of endemic species coincide with intensively collected areas and this approach thus has limited application for conservation planning. The number of site endemics (maximum distance between localities < 10 km) was 243, local endemics (11 km < maximum distance < 70 km) was 102, and regional endemics (71 km < maximum distance < 150 km) was 44, while the total number of South African endemics was 430 (89 % of 484 described species). While grid cells we identify as having the highest number of endemics may not be the only grids with high levels of endemism, as many as 20 endemic species are found within some quarter-degree cells. While patterns are partially explained by a collecting artefact, additional collecting will only increase the number of range-restricted species. The highest levels of narrow endemics occur in the smaller bodied, less mobile millipede families such as the Dalodesmidae, Gomphodesmidae and Odontopygidae, which have radiated in isolated habitats such as forests. Most parts of South Africa are inhabited by a large number of range-restricted endemics. Because of the large number of widely distributed site endemics, it would be impossible to conserve all species in formal state reserves. Millipedes may represent similar patterns of diversity to other soil and saproxylic animals, which all play critical roles in soil nutrient cycles. Although the data are incomplete, given the urgency created by rapid land-use change in South Africa, it is critical that taxon specialists evaluate their data and use these to identify important patterns and trends for improved biodiversity conservation efforts. In addition, efforts should be made to Red List invertebrates to highlight the extent of threats to the major component of biodiversity.

A strategy for the national red-listing of invertebrates based on experiences with Odonata in South Africa
Samways, M.J. 43-52

Abstract: The IUCN Red List of Threatened Species is widely recognized as an authoritative compilation of globally threatened taxa. From an invertebrate perspective it presents a challenging dilemma. As all species are given equal credence, a worm has the same exposure as a whale. Yet there are several million species of invertebrates, thus putting great onus on invertebrate conservationists. South African Odonata species have received considerable conservation focus and have been used to test the most recent IUCN categories and criteria of threat. The importance of overcoming both the taxonomic and perception challenges in invertebrate conservation are discussed. The categorization process is also discussed. Recommendations for South African national redlisting are made, with special reference to the dynamics of such red-listing. A simplified strategy is finally presented, which includes a suggestion for compiling a list of potential focal taxa which in the first instance are not categorized. The species on this list then become a core in field searches, both during wide-scale atlassing and during more focussed threat category assessments.

Dung beetle diversity in South Africa : influential factors, conservation status, data inadequacies and survey design
Davis, A.L.V. 53-65

Abstract: Dung beetles are useful as indicators in conservation and global warming studies owing to their specialized regional and local distribution patterns. However, existing South African data are inadequate for indication at the necessary degree of spatial resolution. To improve the database, survey methods need to be designed according to the spatial and temporal factors that influence dung beetle diversity. Across four major climatic regions, there are seven principal species distribution centres for dung beetles in which activity is influenced primarily by differences in rainfall seasonality and temperature. Across these regions, generic endemism is largely concentrated around the coastline and in montane areas. The conservation status of endemic genera is discussed. At a local scale, spatial diversity is influenced primarily by soil, vegetation and dung type. Maximum local diversity of dung beetles is observed after rainfall and decreases as surface conditions become warmer and drier. After workshop discussions, a coarse-grained, asymmetrical gradsect survey grid has been designed according to vegetative, climatic and land-usage gradients across South Africa. It is suggested that each survey point across these regional gradients should comprise a quarter-degree square in which local ecological gradients should be surveyed for invertebrates. Baited pitfall trapping is an easy method to provide quantitative data for dung beetles across such environmental gradients. Lining up each catch on a tray provides a relatively quick way to compare the specimens, identify the species present, and provide a quantitative assessment of species abundance. Data collection may be conducted on one or more occasions to accommodate seasonal and daily variation in species occurrence. This exercise could identify localities suitable for ecotourism reserves representative of the variation in ecotypes across the country, particularly in coastal, natural grass and wooded regions, where many invertebrate taxa are endangered by habitat fragmentation including some rare dung beetle species.

Diversity and conservation of invertebrates on the sub-Antarctic Prince Edward Islands
Chown, S.L.McGeoch, M.A.Marshall, D.J. 67-82

Abstract: The Prince Edward Islands form a unique component of South Africa's natural estate. Here we present an overview of the diversity of the invertebrate fauna found on Marion and Prince Edward Islands and the conservation threats facing it. The invertebrate fauna at the islands is well known owing to a significant recent effort to sample the entire fauna, although the nematodes remain poorly known. Mite, insect and springtail assemblages differ considerably between habitats and these patterns support an earlier distinction made between the epilithic and vegetated biotopes. Seasonal variation in the abundances of the arthropods is the norm, although the form of this seasonality varies considerably between species and between habitats. Froma regional perspective, the biogeographic affinities of the fauna remain enigmatic. Nonetheless, it seems likely that isolation has been an important contributor to local, indigenous species richness on Marion Island, and speciation has clearly contributed several endemic species to the fauna. Introduced insect species richness is more closely related to mean annual temperature and the number of humans occupying islands in the sub-Antarctic region, and this pattern is reflected locally in the distribution of indigenous and exotic springtails on Marion Island. The introduced species are common in warm, moist habitats, while the indigenous species prefer colder, drier sites. Local climate change, in step with global trends, seems set to have pronounced influences on the invertebrate fauna. Direct effects are likely to take the form of increased abundances of introduced species because of their shorter life cycles and greater fecundity compared to indigenous species, which tend to be long-lived with low reproductive output. Indirect effects are likely to be the result of changes in predation patterns of introduced house mice, and changes in plant communities precipitated by the spread of invasive vascular plants, which in turn have a marked influence on invertebrate assemblages. Undoubtedly the largest conservation threats at the island are the interactions between climate change, introduced species, and human use. In particular, climate change is likely to mean the ready establishment of alien species propagules, while increasing human use is likely to increase propagule pressure. Conservation of the invertebrates at the island will best be served by reduction in human use and stringent enforcement of the provisions of the management plan for these special nature reserves.

Terrestrial invertebrates of Gough Island : an assemblage under threat?
Jones, A.G.Chown, S.L.Gaston, K.J. 83-91

Abstract: The natural communities of Gough Island have the reputation of being amongst the most pristine of any cool-temperate oceanic island. However, Gough Island is relatively depauperate in indigenous invertebrates, and preliminary results of an ongoing terrestrial invertebrate survey have shown that introduced species now equal, or exceed, the numbers of indigenous species in many groups. Furthermore, many of these introductions are likely to have occurred within the last 50 years. Such high rates of recent introductions constitute a significant conservation threat to the indigenous invertebrates and the island's biodiversity as a whole. In addition, endemic invertebrate species are amongst the prey of a non-invertebrate introduction, the house mouse (Mus musculus Linn.). In this paper, we review the present knowledge of the invertebrates of Gough, report on the preliminary observations of the ongoing Gough Island Terrestrial Invertebrate Survey, and discuss the implications of introduced species for the conservation of Gough Island's indigenous species.

Indigenous forests versus exotic eucalypt and pine plantations : a comparison of leaf-litter invertebrate communities
Ratsirarson, H.Robertson, H.G.Picker, M.D.Van Noort, S. 93-99

Abstract: Newlands Forest in the Cape Peninsula National Park consists of a patchwork of indigenous forests, eucalypt and pine plantations as well as fynbos vegetation. We compared selected leaf-litter invertebrate taxa (Hymenoptera, Opiliones and Amphipoda) between the two plantation types and indigenous forest using Winkler bag sifted leaf-litter extractions. Species richness was greatest in the indigenous forest (22 species) followed by the eucalypt (19 species) and pine (17 species) plantations. The Incidence-based Coverage Estimator (ICE), which uses the number of rare species in the samples to estimate the potential maximum number of species, estimated 52 species in indigenous forest, 2.4 times richer than the 22 species estimated for pine and 1.8 times richer than the 29 species estimated for eucalypt. The Argentine ant Linepithema humile, (Hymenoptera : Formicidae) was present in all three forest types and may have been one of the causes of the low invertebrate species richness. We recommend that levels of disturbance in the Newlands Forest area be reduced by consolidating the patches of indigenous forest and fynbos.

A preliminary study of the effect of fire on ants (Formicidae) in a South African savanna
Parr, C.L.Bond, W.J.Robertson, H.G. 101-111

Abstract: To determine the importance of different fire variables in promoting ant diversity in Pilanesberg National Park, South Africa, ants were studied in savanna grassland patches of different post-fire fuel age, and fire frequency. Pitfall traps were set in six grassland sites representing three fire regimes (1 : young (<24 months post-fire) and frequently burned; 2 : young and infrequently burned; 3 : old (4 and 6 years post-fire) and infrequently burned). Species richness declined with decreasing fire influence, being greatest on young and frequently burned plots, and lowest on old and infrequently burned plots. There was pronounced dominance by a few species on young and infrequently burned plots, and greater equitability at other sites. Ant diversity appears to be influenced more by post-fire fuel age than frequency of burning, although there is a need for a wider range of fire frequencies and greater replication to explore this further. Species richness was inversely correlated with the proportion of foliage biomass at ground level. Southern African ant communities may be quite resilient to differences in fire regime, and only a limited amount of fire diversity (young vs old patches) may be necessary to maintain ant diversity.

Conservation of biodiversity in urban environments : invertebrates on structurally enhanced road islands
Whitmore, C.Crouch, T.E.Slotow, R.H. 113-126

Abstract: Urbanization has resulted is severe alteration and destruction of natural habitats. Durban, South Africa, is one of the fastest growing cities in the world and the demand for land is increasing. The Durban Metropolitan Open Space System (D'MOSS) was created for both ecological and social enhancement through an integrated approach to urban open space establishment and management. We assessed a subsection of the D'MOSS for its contribution to biodiversity enhancement. Invertebrates were selected as indicators of diversity. Pitfall trapping was conducted on a seasonal basis on traffic islands from two landscaping management regimes : extensive mown areas (i.e. limited structural diversity) and the inclusion of indigenous and exotic shrubs, herbs and trees (i.e. structurally enhanced). The influence of adjacent remnant natural areas as a source for these islands was also assessed. Species-area and species-distance predictions based on island biogeography theory were tested to determine whether they apply at this small scale. In this study, urban traffic islands accommodated 232 invertebrate morphospecies, i.e. 71 % of the estimated species richness for a larger sampling effort. A total of 23 881 individuals were sampled, 81 % of which were a single species of ant and a collembolan. Species abundance followed expected seasonality (high in summer and low in winter) irrespective of island treatment. While enhanced islands supported a higher richness during spring, as well as a greater number of unique species overall, our results were not conclusive in their support of either the movement of invertebrates along corridors of semi-natural vegetation, or the value of larger areas of urban open space. The lack of independence between distance and area in this study, the limited scale over which diversity was measured, and the influence of multiple sources of emigration are discussed.

Variability in cocoon size in southern African wild silk moths : implications for sustainable harvesting
Veldtman, R.McGeoch, M.A.Scholtz, C.H. 127-136

Abstract: In southern Africa, two indigenous silk moth species, Gonometa postica and G. rufobrunnea (Lepidoptera : Lasiocampidae), produce commercial-quality silk with fibre that rivals that of the domesticated silkworm and thus has potential for commercial utilization. Although extensive harvesting of cocoons is taking place, little is known of the biology of these two species, including the frequency distribution of cocoon and adult sizes. In both species the sexes differ in size, but the extent of these differences has never been formally quantified. Female cocoons are approximately twice as large as male cocoons, and yield more silk fibre. Thus, sex ratios in natural populations will be important when harvesting cocoons. Our aim was to determine if there are differences in sex-specific cocoon size between : the species; host-plant-specific populations; localities within their distribution range; and between first- and second-generation pupae. The sex ratio and frequency of dwarfism in populations were also determined. Both Gonometa species were significantly sexually dimorphic in cocoon length, width and shape and they could be sexed based on size and shape. Cocoon length was a suitable alternative measure to occupied cocoon mass, and may be used as a rough estimate of silk yield. The sex ratio of both species was approximately 1 : 1 and did not differ consistently between generations. Dwarfs were only found in G. postica populations. Cocoon sizes differed significantly between species, the sexes and localities, but not between generations and host-plant-specific populations. The variability in cocoon sizes found at localities would have implications for silk yields, but sex and species are by far the most important determinants of cocoon size. This information will form the basis of a sustainable harvesting programme for Gonometa spp. in southern Africa.

Behavioural ecology of the Karkloof blue butterfly Orachrysops ariadne (Lepidoptera : Lycaenidae) relevant to its conservation
Lu, S-S.Samways, M.J. 137-147

Abstract: The Karkloof blue butterfly, Orachrysops ariadne (Butler) (Lepidoptera : Lycaenidae), is endemic to the Mistbelt grassland of KwaZulu-Natal province, South Africa, and is currently Red-listed as Vulnerable. This study compares the ecological conditions at the four known colonies to assist in making informed decisions regarding its conservation. A large proportion of the grassland in KwaZulu-Natal has been afforested and cultivated, and at least 92 % of the Mistbelt has been transformed, with only about 1 % in good condition remaining. Predictions on the habitat requirements of this species are necessary for developing a conservation strategy and action plan. Here, we also propose O. ariadne as an indicator species for quality Mistbelt grassland. Saving enough of the remaining Mistbelt grassland is crucial, not just for the survival of O. ariadne, but also for the Mistbelt grassland community as a whole.

Conservation management recommendations for the Karkloof blue butterfly, Orachrysops ariadne (Lepidoptera : Lycaenidae)
Lu, S-S.Samways, M.J. 149-159

Abstract: The threatened Karkloof blue butterfly, Orachrysops ariadne (Butler), is endemic to KwaZulu-Natal province, South Africa. Two of the four sites from which it is known are registered as Natural Heritage Sites within Mistbelt grassland. Even with such protection there is no guarantee that the species will survive in the long-term without habitat management. The aim of such management is to optimize the habitat so that it best meets the needs of the butterfly. Effects of the current fire regime on the butterfly, host plant and ant host were evaluated. It is recommended that burning only take place after the larvae have hatched moved underground with the ant host. Using a Global Positioning System and Geographic Information System, core, quality habitat characteristics were defined. In cooperation with the landowner at one site, alien invasive plants are being removed to increase the area of quality habitat. Availability of host plants limits numbers of the butterfly in the field. Guidelines are provided for propagation and introduction of the host plant to provide the butterfly with more oviposition sites.