Online appendix 1: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.

Comparisons of the composition of spider assemblages in three vegetation habitats in Bogor, West Java, Indonesia

“…Based on the NMDS analysis, a considerable difference in spider assemblages was observed among vegetation habitats. Spiders interact indirectly with the vegetation, indicating a structural support availability for webs and active hunting, as well as prey accessibility, influence species composition (Fourie et al 2013). Various research recorded a correlation between the structural complexity of habitats and species diversity (Moorhead et al 2013;Nogueira et al 2016;Stokmane and Spungis 2016;Avila et al 2017;Haddad and Butler 2018).…”

“…According to a habitat heterogeneity hypothesis, plant communities with more functional biodiversity offer additional ecological niches and a greater possibility of resource exploitations by the fauna (Benitez-Malvido et al 2020). Higher spider species richness in forest and oil palm plantations is possibly due to a wider vegetation diversity, leading to an enhanced habitat complexity comprising several territorial niches (Fourie et al 2013;Nardi and Marini 2021). Cornfield habitats appear relatively uniform in structure, which tends to limit the availability of separate niches.…”