Towards a standardized and optimized protocol for rapid biodiversity assessments: spider species richness and assemblage composition in two savanna vegetation types

A semi-quantitative inventory of spider diversity was done in the Blouberg Nature Reserve (BNR) and Western Soutpansberg Conservancy (WSC) situated in the Savanna Biome of the Limpopo Province, South Africa. Two hundred and ninety-six samples of one person-hour work each, comprised of five methods (vegetation beating, sweep netting, aerial hand collecting, ground hand collecting and leaf litter sifting) were divided between four relatively homogenous sites (plant communities) within a vegetation type of the BNR and WSC, respectively, an average of 37 per site. In addition, 25 pitfall traps were left open for a total of 20 days in each of the eight plant communities, 200 in total. We collected 1328 adult spiders representing 186 species of which 31% were singletons in the BNR vegetation type and 909 spiders in 222 species of which 41% were singletons in the WSC vegetation type. The number of species present was estimated using six estimators. The estimates varied between 233 and 307 for the BNR and 302 and 386 for the WSC. Inventory completeness was more than 70%. However, the fit to a lognormal distribution suggests that there are 370 species (750 000 individuals) and 445 (850 000 individuals) species in the universes (16 ha) sampled within the two vegetation types. Collector experience had no effect on the results of the inventory, whereas time of day had a very small yet significant effect. Seasonality only affected abundance and richness, but not assemblage composition. Sampling methods used had the biggest effect on our results. These results are used to design an optimized sampling protocol for standardized inventories in the Savanna Biome.African Zoology 45(2): 273–290 (October 2010

Associations of spiders of the genus Peucetia (Oxyopidae) with plants bearing glandular hairs

Two common South American species of lynx spiders, Peucetia rubrolineata and P. flava (Oxyopidae), were surveyed on three localities in southeastern Brazil to determine plant choice. Both species were found to be associated with plants bearing glandular trichomes. A literature review and complementary data show that ten Peucetia species are associated with up to 55 plant species bearing glandular trichomes in at least 20 distinct vegetation types (phytophysiognomies) in more than 36 localities in the Neotropical, Neartic, Afrotropical, and Paleartic regions. The main plant families used by the spiders were Solanaceae, Asteraceae, and Melastomataceae. The specialization of the Peucetia species for plants bearing glandular trichomes may have evolved because insects adhered to these sticky structures may be used as prey by the spiders.39222122

Effects of a fast-burning spring fire on the ground-dwelling spider assemblages (Arachnida: Araneae) in a central South African grassland habitat

Fire is widely used as a management strategy in grasslands to maintain vegetation structure and improve grazing quality for large herbivores. The impacts of burning on invertebrates in South Africa remain poorly understood. A study was initiated in spring 2005 to determine the impact of a fast hot burn on ground-dwelling spider assemblages in a grassland habitat in the central Free State. Pitfall traps were set out at six sites in the reserve, with three sites each in the burnt and unburnt areas, to sample spiders over a 12-month period. A total of 5 253 spiders were collected, representing 33 families and 120 species. Spider abundance was significantly lower in the burnt (n = 1 956) than unburnt sites (n = 3 297), and burnt sites had, on average, considerably fewer species than unburnt sites. The dominant families in the burnt sites were Lycosidae (29.5%), Gnaphosidae (16.9%), Ammoxenidae (9.6%) and Zodariidae (5.7%), whereas Ammoxenidae (22.7%), Lycosidae (20.6%), Gnaphosidae (15.3%) and Amaurobiidae (10.2%) dominated the unburnt sites. Of the nine most abundant families collected, only Caponiidae were more abundant in the burnt than unburnt sites. Our data suggest that fast-burning hot spring fires cause a considerable initial post-fire decline in spider abundance, and have a negative influence on the abundance as well as the resistance of assemblages to disturbances other than fire (e.g. rain). However, most of the dominant families had abundances comparable to unburnt areas within a year post-burn.http://www.tandfonline.com/loi/tafz202016-12-31hb201