Ansie S. Dippenaar-Schoeman

DIVERSITY OF SPIDERS (ARANEAE) IN A SAVANNA RESERVE, NORTHERN PROVINCE, SOUTH AFRICA

Abstract In this study our objectives were to describe the diversity and characteristics of spider families occurring in a range of habitat types within a typical savanna ecosystem, to assess the influence of habitat type and seasonality on spider diversity and to determine levels of similarity between habitat types based on species composition. The study was conducted at Makalali Private Game Reserve, Northern Province, South Africa. Five different habitat types were sampled using four trapping techniques (sweeping, beating, active searching and pitfalls). A total of 4832 individuals including 268 species from 38 families were sampled during the study. Families showed varying degrees of habitat fidelity with some being widespread and abundant while others were restricted to a single site and were locally rare. Sites with similar habitat types showed a similarity in spider family composition. All sites have unique species compositions and overall diversity, evenness and richness of spiders do not differ with habitat type. However, analyses of functional groups, e.g., web builders and plant wanderers, showed the positive influence of structural complexity of the habitat. The presence of unique species in all habitats highlights the importance of conserving as wide array of representative habitats within ecosystems. The appearance of strong seasonal patterns in species composition also has important implications for the development of protocols for sampling species diversity. The savanna has a surprising diversity of spiders when compared to other biomes surveyed in South Africa. Factors influencing this diversity beyond the broader habitat variables measured in this study need to be investigated.

Report of the General Secretary for 2008 : annual report

CENTENARY CONGRESS OF THE SOCIETY To commemorate the Centenary of receiving its Royal Charter, the Royal Society of South Africa held a Centenary Congress on 17 and 18 April 2008 at the Breakwater Lodge in Cape Town. The theme of the Congress was The Value of Science: looking Back and Looking Forward. The idea was to celebrate the achievements of the Society, especially over the last 30 years since the publication of A History of Scientific Endeavour in South Africa, edited on behalf of the Society by former President A.C. Brown FRSSAf, and to examine the future role of the Society in South African science. The Congress was also planned as a celebration of the inter-disciplinary character on which the Society prides itself. The Opening Address was presented by Albert van Jaarsveld FRSSAf and the Congress comprised three elements: invited plenary lectures covering major fields of South African science, poster sessions dedicated to current research projects, and a discussion on the future of science in South Africa. Invited speakers, all of whom are Fellows or Members of the Society, were requested to discuss their field of research in terms of the theme of the Congress in such a way as to be readily intelligible to non-specialists. There were four poster sessions, in two parallel sessions, displaying a wide variety of research, much of it by students, which bodes well for the future. These sessions, during which authors presented their work, took place in front of the posters to facilitate discussion. The Congress was concluded with a discussion on the outlook for science in South Africa, which took the form of position statements by panel members and subsequent opening of the discussion to the floor. The Centenary Banquet was held at the nearby Commodore Hotel on the evening of 17 April. This banquet included elements of the annual banquet, such as the induction of new Fellows and presentation of medals. As befits a unique occasion, it also saw the induction of two new Honorary Fellows (George F.R. Ellis and Brian Warner) and the presentation of his Certificate to Phillip V. Tobias FRS, Hon. FRSSAf. The third new Honorary Fellow, William H. Frankel, was unable to attend at the last minute; he was subsequently inducted at a lunch in Cape Town. On the decision of Council, Centenary medals were awarded to Maciej Soltynski MRSSAf and Anthony J. Ribbink FRSSAf (Treasurer and Vice President, respectively) for exceptional service to the Society. The banquet address on this occasion was delivered by Phillip Tobias, a former President, on the topic of The Value of Science: Looking Back.Centenary Congress of the Society To commemorate the Centenary of receiving its Royal Charter, the Royal Society of South Africa held a Centenary Congress on 17 and 18 April 2008 at the Breakwater Lodge in Cape Town. The theme of the Congress was The Value of Science: looking Back and Looking Forward. The idea was to celebrate the achievements of the Society, especially over the last 30 years since the publication of A History of Scientific Endeavour in South Africa, edited on behalf of the Society by former President A.C. Brown FRSSAf, and to examine the future role of the Society in South African science. The Congress was also planned as a celebration of the inter-disciplinary character on which the Society prides itself.

Response of ground-dwelling spider assemblages (Arachnida, Araneae) to Montane Grassland management practices in South Africa

Frequent and extensive burning practices coupled with intensive grazing management are known to impact negatively on the vegetation diversity of grassland ecosystems. Few studies have investigated the impacts on spider diversity and community structure as a result of these management practices, and no studies have been conducted in high mountain grasslands on how these spider assemblages are influenced by this form of management. Here, we present the results of a study conducted in the Mpumalanga grasslands on the eastern escarpment of South Africa. Ground‐dwelling spiders were sampled in the summer season from 180 pit‐fall traps in five study sites that varied from either being burnt annually and grazed heavily, burnt biennially and conservatively grazed, to communal land with no set management practice. Variations between sites were assessed and based on spider species composition and assemblage structure. A total of 1145 individuals were collected representing 86 species from 60 genera and 43 families. Our results show that a majority of genera in these grasslands were represented by very few individuals, where a total of 37 species were represented by singletons and 17 species that were doubletons. The most abundant families were the Lycosidae (64.3%), Gnaphosidae (9.0%), Zodariidae (5.3%), Linyphiidae (4.7%) and Salticidae (3.1%). Grazing intensity and fire frequency had no measurable effect on ground‐dwelling spider abundance diversity or assemblage structure. Only when rare or single species occurrence was included, was there some form of association with sites. This study has provided for the first preliminary inventory of ground‐dwelling spiders for this habitat.

The faunistic diversity of spiders (Arachnida: Araneae) of the Savanna Biome in South Africa

Invertebrates include more than 80% of all animals, yet they are severely under-represented in studies of southern African diversity. Site biodiversity estimates that ignore invertebrates, not only omit the greatest part of what they are attempting to measure, but also neglect major contributors to essential ecosystem processes. All available information on spider species distribution in the South African Savanna Biome was compiled. This is the largest biome in the country, occupying over one third of the surface area. A total of 23 739 records from 1260 localities were recorded in the South African Savanna Biome until the end of 2010. This included 1230 species represented by 381 genera and 62 families. The last decade has seen an exponential growth in the knowledge of the group in South Africa, but there certainly are several more species that have to be discovered, and the distribution patterns of those listed are partly unknown. Information is summarised for all quarter-degree squares of the biome and reveals considerable inequalities in knowledge. At a large scale the eastern region is much better surveyed than the western parts, but at finer scales throughout the region, several areas have little information. The Salticidae is the most diverse family (162 spp.) and also has the most endemic savanna species (42 spp.). An endemicity index indicates that 366 species are endemic to the biome, with 322 species that are near endemics, i.e., also occurring in an adjacent biome. An abundance index (1–3) was also calculated for each species based on numbers sampled. A rarity index for each species gives a preliminary indication of their conservation importance. Patterns of guild composition are summarised and species known to play a role as predators in agro-ecosystems found within the biome are also discussed.

FOOD STORAGE BY A WANDERING GROUND SPIDER (ARANEAE, AMMOXENIDAE, AMMOXENUS)

Abstract Members of genus Ammoxenus are known predators of harvester termites (Hodotermes mossambicus). An A. amphalodes female was observed catching and paralyzing a termite in the field. The paralyzed termite was deposited in a silk sac with other paralyzed termites. This confirms that Ammoxenus spp. use different methods of catching and utilizing prey. Termites are either killed and fed upon or paralyzed and stored for feeding at a later time.

A review of the cave spiders (Arachnida: Araneae) from South Africa : research article

An assessment of the present status of spiders (Araneae) from caves in South Africa was undertaken. A total of 44 species from 33 genera and 21 families are known from 44 caves in South Africa. Of the species collected, only 10 species are regarded as true cave spiders (troglobites), while 18 are troglophiles, found both inside and outside caves. The rest of the species (15) are cave accidentals and they are found mainly around the entrances. Baseline information is needed for the development of cave management programmes to guarantee the sustainable conservation of cavernicolous spiders. This study forms part of the South African National Survey of Arachnida (SANSA).

Burrow structure and microhabitat characteristics of Nesiergus insulanus (Araneae : Theraphosidae) from Fregate Island, Seychelles

Abstract The burrow structure and microhabitat variables of the little known theraphosid Nesiergus insulanus Simon 1903 were determined on Frégate Island, Seychelles. The species constructed burrows in fossorial substrates, including rocks, leaf litter and bare soil as well as on the trunks of decaying trees, both recumbent and standing. The majority of burrows were predominantly found in sandy loam soil with partial protection from the sun. The density of burrows was determined to be weakly positively correlated to soil and substrate type and strongly negatively correlated to degree of exposure to the sun. The pH of the soil in which burrows are found was not significantly related to burrow sites, and variability in burrow structure was revealed. Burrow aggregations vary from single burrows to aggregations exceeding 100, distributed randomly.

The Distribution and Population Status of Nesiergus insulanus Araneae: Theraphosidae: Ischnocolinae) on Frégate Island, Seychelles

Summary The theraphosid Nesiergus insulanus is a member of a genus endemic to the Seychelles archipelago. Very little is known about the finer-scale distribution, density, and total population size of the species, knowledge of which is essential for conservation purposes. We used transect sampling to estimate these variables on Frégate Island. We show that the species is widely distributed, but geographically restricted as a result of fragmentation due to human activity. Where found, densities can be very high (>100 m-2). The total population on the island was estimated to be well over 100,000, although limitations to dispersal ability may be of conservation concern.

Aspects of the ecology and behaviour of the Seychelles theraphosid Nesiergus insulanus (Arachnida: Araneae: Theraphosidae)

ABSTRACT Aspects of the ecology and life history of the little known theraphosid Nesiergus insulanus are determined on Frégate Island in the Seychelles archipelago. The general behaviour of this species is revealed to be comparable to that of other theraphosids, with field and captive observations establishing that they are a generalist and opportunistic species. The defensive behaviour of the species is determined to be based primarily on the avoidance of conflict situations, with overt aggressive behaviour seldom displayed. Although the opportunistic existence that this species has developed is probably obligatory due to their sedentary lifestyle and limited availability of resources, this behaviour nonetheless allows the species to occupy diverse habitats and exploit niches unavailable to more specialized species.