Arboreal spider assemblages associated with four tree species in the Grassland Biome of central South Africa (Arachnida: Araneae)

Abstract

Foliage-dwelling spiders (Arachnida: Araneae) were collected from four common tree species in the Grassland Biome of central South Africa by beat-sampling. The aim of the study was to assess possible differences in the assemblage structure and species composition of spiders that could be attributed to structural differences in the vegetation. In total, 1909 spiders representing 17 families and 54 species were collected. Four families were dominant in abundance, together accounting for more than 73% of the spider fauna: Miturgidae (23.1%) was most numerous, followed by Araneidae (17.7%), Thomisidae (16.7%) and Philodromidae (15.4%). Overall spider abundance and species richness did not differ significantly among the four tree species, decreasing slightly from Acacia karroo (n0495, 38 spp.) to Olea europaea africana (n0479, 32 spp.), Buddleja saligna (n0477, 36 spp.) and Searsia lancea (n0458, 37 spp.). However, significant seasonal differences were detected for each tree. Generally, abundance and species richness were lowest during winter and highest during summer on all four species. Our findings suggest that vegetative and habitat structure and complexity have a limited influence on the abundance and species richness of tree-dwelling spiders in grassland habitats, although these factors may affect the assemblage structure on different tree species.

High genetic diversity of spider species in a mosaic montane grassland landscape

“…In certain instances, an agricultural area of 100 m can present a complete barrier to gene flow for certain spider species, due to removal of natural vegetation [111]. Some spider species are also known to prefer certain types of vegetation over others [60,[112][113][114][115], which may impact their ability to colonise new habitats. Such preference is often documented in orb-weaver species, such as N. subfusca, in which vegetation complexity often determines site selection [116][117][118].…”

“…P.S. Green) above three other tree species studied [60]. Additionally, there is no record of sociality occurring in the genus Pherecydes.…”

“…The 123 species of Neoscona Simon, 1864 (Araneidae) occupy a mostly pantropical distribution [46,57], with the investigated orb-weaver N. subfusca being widely distributed throughout the Afrotropical region, particularly in the Savanna and Grassland biomes of South Africa [49][50]52]. Individuals have been collected from a variety of grass, herb and foliage types across a number of habitats [58][59][60], where they maintain a preferential solitary [61], plantdwelling lifestyle due to their construction of symmetrical orb-webs. Neoscona subfusca is often yellow to light brown in colouration, with a covering of white hairs and darker abdominal markings (S1C and S1D Fig) [62].…”

Ground-dwelling spider assemblages in contrasting habitats in the central South African Grassland Biome

“…Only as recently as three decades ago were the first ecological studies on spiders undertaken in the biome, focusing on the biodiversity of ground-dwelling Jansen et al 2013;Lotz, Seaman & Kok 1991;Van den Berg & DippenaarSchoeman 1991), plant-dwelling (Dippenaar-Schoeman, Hamer & Haddad 2011;Fourie et al 2013;Haddad 2005;Neethling & Haddad 2013), litter-dwelling (Butler & Haddad 2011) and termitophilous assemblages (Haddad & Dippenaar-Schoeman 2002. Different species are adapted to particular microhabitats within grasslands, either living on the ground, on grasses or on foliage of woody plants, with few species abundant in multiple strata .…”

“…Only three of the aforementioned studies have investigated finer scale differences in spider assemblages associated with different plant species, notably litter-dwellers (Butler & Haddad 2011) and foliage-dwellers (Fourie et al 2013;Neethling & Haddad 2013). However, assemblage structure in contrasting vegetation communities has so far only been investigated for grass-dwellers in structurally variable grasslands (Fourie et al 2013).…”