The Savanna Biome is the largest Biome in South Africa and occupies over one third of the whole area. It is characterised by a grassy ground layer and distinct upper layer of woody plants. Where the upper layer is short, it is known as shrub veld, where dense, as woodland, and the intermediate stages are known as bush veld. The major delimiting factors are rainfall, which varies from 235 to 1000 mm per year, and fire.

More than 600 sites in the Savanna Biome have so far been sampled. This includes at least 11 sites (Dendron, Roodeplaat Nature Reserve, Rustenburg Nature Reserve, Nylsvley Nature Reserve, Makelali Nature Reserve, Kruger National Park, Springbok Flats, Marble Hall, Rust de Winter, Nelspruit, Lajuma, Ndumo Game Reserve, Polokwane Nature Reserve, Hluhluwe-iMfolozi Nature Reserve, Tembe Elephant Park) where long-term surveys have been undertaken for periods of one to five years. These surveys include data from conserved areas, farms and agro-ecosystems.

PROJECTS UNDERWAY IN THE SAVANNA BIOME

PROJECT: Kruger National Park/Opuntia

A total of 1100 spiders, represented by 45 species, were identified from the Kruger National Park as part of a project to examine habitat specificity of beetles and spiders and variation in these assemblages, within a habitat system characterized by different levels of prickly pear (Opuntia stricta) invasions. Groups of species that are characteristic of each O. stricta invasion level (indicators) were identified, as well as species that may be used to monitor changes in invasion levels (detectors). Detector species will be used to predict change in the intensity of O. stricta invasions. The project is part of the MSc of Kyle Harris. He is registered at the University of Pretoria and the project is funded by the Invasive Alien Research Programme (IAS).

PROJECT: Hluhluwe/iMfolozi Nature Reserve / Chromolaena

In another MSc project, of Mandisa Mgobozi, a total of 450 spiders represented by 48 species was collected from the Hluhluwe/iMfolozi Nature Reserve as part of a survey to study spiders as bioindicators of the effect of the invasive plant Chromolaena odorata on invertebrate diversity. Nearly all the protected areas in KwaZulu-Natal have already been aggressively colonized by this weed. Historical maps showing C. odorata invasion within the reserve were analysed and areas that have been invaded for ca 20, 10 years and less than 1 year were identified and sampled. This study also determined the effects of mega herbivores on invertebrate diversity, compared the diversity and density patterns of spiders in relation to the different rainfall regimes of Hluhluwe/ iMfolozi, and also determined the difference between the diversity indices of the different grass types.

PROJECT: Survey Polokwane Nature Reserve

Two students of the University of Limpopo are busy writing up their MSc studies undertaken in the Polokwane Nature Reserve.

Mokgadi Modiba studied the abundance and species richness of the spiders (Arachnida: Araneae) associated with open savanna, woodland and the Polokwane plateau false grassland. Her study started in March 2005 and ended in February 2006. Three habitat types were sampled namely: open savanna dominated by Acacia tortilis trees; woodland with Acacia rehmanniana as the dominant tree species and the very unique Polokwane Plateau False Grassland, the last remaining undisturbed example of this very localized vegetation type. Spiders were caught using four different methods namely active searching, sweep netting, tree beating and pitfall trapping. The aim of the study was to collect and compare spiders associated with different vegetation types within the reserve, using abundance and species richness indices and to compile the first checklist for the reserve. A total of 7821 specimens were caught belonging to 33 families and 95 genera representing more than 190 species.

Thembile Khoza studied the abundance and species richness of the spiders associated with three different vegetation types selected as sampling sites, namely Acacia karoo / Rhus pyroides riverine thicket; a northern slope granite outcrop site and an Aloe marlothii thicket on a shale outcrop. The survey started in the beginning of March 2005 and continued until the end of February 2006. Four collection methods namely active searching, sweep netting, tree beating and pitfall trapping were used to sample the spiders. Sampling was done once a month, for four consecutive days per sampling site, using a different method every day, but with the pitfall traps open for the whole period. A total of 6033 specimens belonging to 32 families, 115 genera and more than 149 species were collected.

PROJECT: Arachnida survey of the Ndumo Nature Reserve

KwaZulu-Natal is possibly one of the best sampled provinces in South Africa with regards to arachnids. However, some areas are in desperate need of attention and the fauna is quite poorly known. Maputaland, an area extending from St. Lucia northwards into southern Mozambique, is regarded as a Centre of Endemism and biodiversity hotspot. Unfortunately, little was known of the arachnid fauna of the area, and several SANSA studies were initiated since 2000 to address this problem.

KwaZulu-Natal is possibly one of the best sampled provinces in South Africa with regards to arachnids. However, some areas are in desperate need of attention and the fauna is quite poorly known. Maputaland, an area extending from St. Lucia northwards into southern Mozambique, is regarded as a Centre of Endemism and biodiversity hotspot. Unfortunately, little was known of the arachnid fauna of the area, and several SANSA studies were initiated since 2000 to address this problem.

The first major study dealt with the arachnids of the Ndumo Game Reserve, situated in western Maputaland near the foothills of the Lebombo Mountains. Since 2000, twelve sampling trips varying in duration from one to four weeks were undertaken with the main aim of sampling all of the eight broad habitat types in the reserve. In total, 457 species of arachnids were collected in this period, of which 431 species are spiders (Haddad et al. 2006). This represents the highest diversity of spiders known from any of South Africa's conservation areas. What is exceptional is that each trip has yielded additional new records, and this pattern has not yet stopped. Even during field work in 2007 several additional new records were reported. This indicates that the total diversity is not yet known, and may ultimately exceed 500 species.

Studies continue into the biodiversity of spiders and beetles in four contrasting habitats in the reserve (sand forest, broadleaf woodland, Mahemane thicket and Acacia nigrescens woodland) based on pitfall trapping data. A fifth site, on the Pongola river floodplain, unfortunately had to be abandoned due to extensive flooding during January 2007. Initial results of this study suggest that broadleaf woodland and Mahemane thicket have the most unique faunas and also higher densities of epigeic spiders compared to the other two habitats.

Apart from biodiversity work, studies are underway to investigate the biology and feeding ecology of several spiders. The first of these studies, on the new termitophagous salticid Stenaelurillus natalensis, was recently published (Haddad & Wesolowska 2006). This species is apparently a prey specialist of Odontotermes badius  termites. Studies continue on two specialist myrmecophages, the salticid Mexcala elegans and the thomisid Sylligma sp. The latter is possibly a new species that will be described by Alet Honiball as part of her MSc studies on Afrotropical Dietinae. Interestingly, Mexcala elegans is a mimic of Polyrachis gagates ants, but feeds on a variety of other ants as well. No other insects have been observed as prey. The Sylligma sp. is a mimic and exclusive predator of Myrmicaria natalensis ants. This survey is undertaken by Charles Haddad at the University of the Free State.

PROJECT: Thuthuka project funded by NRF

The first phase of the study focused on small-scale determinants of spider assemblages in the Savanna Biome while the second phase contribute towards a better understanding of the mechanisms, both biological and anthropogenic, that account for changes in environmental variables and that translate into altered species richness and species turnover (b-diversity) patterns at the regional scale as this is an important component of efficient conservation planning. Data on spider assemblages (collected during the first component of this study together with previously collected data), environmental variables (e.g. climate data), land-cover information, and human density values will be used to examine species distribution patterns at the regional scale.

Problem identification

To understand species richness patterns in spider assemblages across the Savanna Biome and the underlying processes responsible for these patterns, it is important not only to examine the importance of biological processes as explanatory variables of species richness, but also to examine what influences do landscape transformation and human population size have on species biogeographic patterns. These factors pose the single most important threat to biodiversity, and are often overlooked.
To contribute towards our poor knowledge of most arachnid families from South Africa in terms of their taxonomy, ecology and distribution: (i) update the check lists of spiders found in the Soutpansberg region and in the Savanna Biome region; (ii) further determine the number of spider species presently protected in conserved areas in the Soutpansberg and Savanna Biome; and (iii) describe new spider species collected.
To address conservation related questions at two very different, but relevant spatial scales at which land-use decision makers will increasingly have to consider ways of incorporating the dynamic nature of the environment into their conservation strategies if they are to succeed in their long-term goals of sustainable development. This is especially true based on the fact that the physical and biotic landscape we live in is not static.

Thuthuka—Work Plan

2007

Extraction and verification of data from museum specimen databases on specimens previously collected in Savanna Biome.
Literature survey on published records of arachnids from Savanna Biome .
Obtain data on climatic variables, landscape transformation and human population density at the finest resolution possible for the Savanna Biome – this will be done from existing data sets.
Produce climatic variables and human population density values for the Savanna Biome under changing environmental scenarios.
Conduct a literature search on the biogeographical affiliations of spider assemblages found between the Soutpansberg, Pondoland and the Maputaland Centre of Plant Endemism.
Address the main research questions asked by combining the Savanna Biome spider and other arachnids, environmental, human population and land use data in a GIS and statistically analyse the emergent patterns.

2008

Undertake spider-collecting trips within the Savanna Biome region to complete information on spider distributions in areas where data are lacking for this biome (SANSA).
Sorting and identification of collected specimens (ARC,SANSA, Post-doc).
Complete the main research questions asked by combining the Savanna Biome spider and other arachnids, environmental, human population and land use data in a GIS and statistically analyse the emergent patterns.
Writing up the PhD thesis and publication of papers
Development of other technology information products such as CD-ROMS, posters, regional check lists.
Incorporate data into existing biodiversity databases such as the South African National Survey of Arachnida (SANSA) the African Arachnida Database.

PROJECT: Survey Nylsvley Nature Reserve

Spiders have been collected over a period of 30.years from the Nylsvley Nature Reserve, South Africa. The spider check list contains 173 species, 132 genera from 37 families. The Thomisidae is the most diverse spider family with 34 species (19.6 % of total) followed by the Salticidae with 19 spp. (10.9 %) and Araneidae with 18 spp. (10.4 %). The majority of species (123) are wandering spiders, while 50 spp. are web dwellers. The ground dwelling spiders comprise 60 spp. from 24.families with 44 spp. that are free-living, 7 spp. live in burrows and 9 spp. constructing webs on or close to the ground. From the plant layer 113 spp. from 8 families have been collected, of which 36 were web builders and 74 free living on plants. A total of 158 species, are new records for the reserve and 6.5 % of the total known South African spider fauna are protected in the reserve. The survey is undertaken by the Spider Research Centre at ARC-PPRI. (Back to Projects)

PROJECT: Survey Welgevonden Nature Reserve

A new survey started in the Welgevonden Nature Reserve under leadership of Hanno Kilian

PUBLISHED RESULTS ON SAVANNA BIOME

Dippenaar-Schoeman, A.S. &. Leroy, A. 2003. A check list of the spiders of the Kruger National Park, South Africa (Arachnida: Araneae). Koedoe 46: 91-100.

Dippenaar-Schoeman, A.S., Van den Berg, A.M. & Van den Berg A. 1989. Species composition and relative seasonal abundance of spiders from the field and tree layers of the Roodeplaat Dam Nature Reserve. Koedoe 32: 51-60.

Foord, S.H., Dippenaar-Schoeman, A.S. & Van der Merwe, M. 2002. A check list of the spider fauna of the Western Soutpansberg, South Africa (Arachnida: Araneae). Koedoe 45: 35-43.

Foord S. & Dippenaar-Schoeman, A.S. 2003. Spiders (Araneae). A first synthesis of the environmental, biological & cultural assets of the Soutpansberg In: I.A.W. Macdonald, I. Gaigher, R. Gaigher & K. Berger. http://www.soutpansberg.com/workshop/index.htm.

Haddad, C.R. & Dippenaar-Schoeman, A.S & Wesolowska, W. 2006. A checklist of the non-acarine arachnids (Chelicerata: Arachnida) of the Ndumo Game Reserve, Maputaland, South Africa. Koedoe 49: 1-22.

Modiba, M.A., Dippenaar, S.M. & Dippenaar-Schoeman, A.S. 2005. A checklist of spiders from Sovenga Hill, an inselberg in the Savanna Biome, Limpopo Province, South Africa (Arachnida: Araneae). Koedoe 48: 109-115.

Whitmore, C., Slotow, R., Crouch, T.E. & Dippenaar-Schoeman, A.S. 2001. Checklist of spiders (Araneae) from savanna ecosystem, Northern Province, South Africa: including a new family record. Durban Museum Novitates 26: 10-19.

Whitmore C., Slotow, R., Crouch, T.E. & Dippenaar-Schoeman, A.S. 2002. Diversity of spiders (Araneae) in a savanna reserve, Northern Province, South Africa. Journal of Arachnology 30: 344-356.

PAPERS ON SPIDERS IN AGRO-ECOSYSTEMS IN THE SAVANNA BIOME

Dippenaar-Schoeman, A.S. 1979. Spider communities in strawberry beds: seasonal changes in numbers and species composition. Phytophylactica 11: 1-4.

Van den Berg, A.M., Dippenaar-Schoeman, A.S. & Schoonbee, H.J. 1990. The effect of two pesticides on spiders in South African cotton fields. Phytophylactica 22: 435-441.

Van den Berg, M.A., Dippenaar-Schoeman, A.S., Deacon V.E. & Anderson, S.H. 1992. Interaction between citrus psylla, Trioza erytreae (Hem. Triozidae), and spiders in an unsprayed citrus orchard in the Transvaal Lowveld. Entomophaga 37: 599-608.

Dippenaar-Schoeman, A.S., Van den Berg, M.A. & Van den Berg, A.M. 2001. Spiders in macadamia orchards in the Mpumalanga Lowveld of South Africa: species diversity and abundance (Arachnida: Araneae). African Plant Protection 7: 36-46.

Dippenaar-Schoeman, A.S., Van den Berg, M.A. & Van den Berg, A.M. 2001. Salticid spiders in macadamia orchards in the Mpumalanga Lowveld of South Africa (Arachnida: Araneae: Salticidae). African Plant Protection 7: 47-51.

Dippenaar-Schoeman, A.S., Van den Berg, A.M., Van den Berg, M.A. & Foord, S.H. 2005. Spiders in avocado orchards in the Mpumalanga Lowveld of South Africa: species diversity and abundance (Arachnida: Araneae). African Plant Protection 11: 8-16.

PAPERS IN PRESS AND IN PREPARATION

Honiball, A.S., Haddad, C.R., Dippenaar-Schoeman, A.S., Slotow, R. & Van Rensburg, B.J. (in prep). Spiders (Arachnida: Araneae) as indicators of elephant-induced habitat changes in endemic sand forest, Maputaland, South Africa.

Dippenaar, S.M., Dippenaar-Schoeman, A.S., Modiba, M.A. & Khoza, T.T. (in press). A checklist of the spiders (Arachnida, Araneae) of the Polokwane Nature Reserve, Limpopo Province, South Africa. Koedoe.

Dippenaar-Schoeman, A.S. & Van den Berg, A. (in prep). A check list of the spiders of the Nylsvley Nature Reserve, South Africa (Arachnida: Araneae).

Dippenaar-Schoeman, A.S. & Simangale S.G. (in prep). A check list of the spiders of the Rustenburg Nature Reserve, South Africa (Arachnida: Araneae).

Harris, K., Janse van Rensburg, B., Robertson, M., Coetzee, J. & Dippenaar-Schoeman, A.S. (in prep). How best to collect spiders (Araneae) in an alien plant invaded African savanna: using the Kruger National Park as a case study

Mafadza, M.M., Foord, S.H., Van Rensburg, B.J. & Dippenaar-Schoeman, A.S. (in prep). Vegetation structure, spider diversity, and small-scale heterogeneity in spider (Arachnida: Araneae) assemblages in a Savanna Biome, Soutpansberg, South Africa.

At present a total of 57 spider families represented by 282 genera and 1 100 species have been recorded from the Savanna Biome. More than 400 sites have been sampled in this biome so far.