Ecology of the plant-dwelling spiders (Arachnida: Araneae) of the Erfenis Dam Nature Reserve, South Africa

Abstract

As part of the South African National Survey of Arachnida in the Grassland Biome, foliage-dwelling and grass-dwelling spiders (Arachnida: Araneae) were collected in the Erfenis Dam Nature Reserve in the central Free State Province from November 2005 to August 2007. Foliage-dwelling spiders were collected from three common tree or shrub species (Acacia karroo, Searsia ciliata and Searsia lancea) and grass-dwellers from four contrasting grasslands (uniform Themeda triandra, mixed, weedy and woodland grasslands). From the grass layer, 1649 spiders were collected, representing 15 families and 82 species, whilst 496 tree-dwelling spiders were collected that represented 17 families and 52 species. There was some overlap in the fauna of the two strata, resulting in a total of 108 species from 18 families being collected. The Araneidae, Philodromidae, Salticidae and Thomisidae were consistently the most abundant in all grassland types and tree species, although Salticidae were scarce on A. karroo. Assemblage analysis indicates high similarity and overlap in the fauna of the four grassland types, suggesting that the structural complexity of grasslands has a limited effect on species composition. In contrast, the foliage-dwelling assemblages were more distinct, with only some overlap between the faunas of S. ciliata and A. karroo, suggesting a stronger vegetation structural effect in shaping arboreal spider assemblages. The isolation of trees and shrubs within the extensive grassy habitat may contribute to the more unique fauna and lower species richness of the woody vegetation. Conservation implications: This study uncovered a rich diversity of plant-dwelling spiders from central South Africa. Grassland faunas show considerable temporal variation and some variability in microhabitat preferences, and sampling protocols should take this into account when spiders are considered in management plans and biodiversity surveys in reserves and private land.

South African National Survey of Arachnida (SANSA): review of current knowledge, constraints and future needs for documenting spider diversity (Arachnida: Araneae)

“…The PAs include nature reserves, a national park and a botanical garden. Published records include surveys in the Free State National Botanical Gardens (Butler & Haddad 2011;Neethling & Haddad, 2013) and the Erfenis Dam Nature Reserve (Fourie et al, 2013), while surveys are presently underway in the Kalkfontein Dam Nature Reserve (Josling & Lotz, 2014), Amanzi Private Game Reserve (Butler & Haddad, 2014) and Amohela-ho-Spitskop Conservancy .…”

“…An illustrated guide to the spiders of the Grassland Biome is also available (DippenaarSchoeman & Haddad, 2014). Grassland survey results have focused on the Free State (Lotz et al, 1991;Haddad & Dippenaar-Schoeman, 2002Haddad, 2005;Butler & Haddad, 2011;Fourie et al, 2013;Neethling & Haddad, 2013), Gauteng (Van den Berg & Dippenaar-Schoeman, 1991b), Mpumalanga , Eastern Cape (Dippenaar- and KwaZulu-Natal provinces (Van der Merwe et al, 1996). Spiders have also featured in studies using functional feeding groups as indicators of habitat quality (Kaiser et al, 2009) and taxonomic surrogates (Buschke & Seaman, 2011), and burning effects on invertebrates (Uys et al, 2006;Little et al, 2013).…”

“…Initially, the project aimed to assess the impact of controlled burning on the ground-dwelling arachnid fauna, but the opportunity was taken to investigate the spider faunas of three common tree species and also the spider communities in four contrasting grassland types in the reserve (Fourie et al, 2013). Haddad et al (in press) found significantly lower abundance and species richness in the burnt grassland compared to undisturbed grassland.…”

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

“…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).…”

“…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 .…”