Foliage Density of Branches and Distribution of Plant‐Dwelling Spiders¹

Abstract

We compared the abundance of foliage‐living spiders among seven widespread plant species comprising a gradient of levels of structural complexity in a tropical savannah‐like region in southeastern Brazil. Spider abundance among plant species was positively related to the foliage density of their branches. A field experiment using artificial branches was carried out to isolate foliage density effects on spider abundance, thus controlling both biomass and texture effects. Artificial branches were attached to branches of three plant species with similar foliage density, Baccharis dracunculifolia, Diplusodon virgatus, and Microlicia fasciculata. Two treatments were set up: artificial branches with higher foliage density attracted more spiders than those with lower foliage density. The guild structure of hunting spiders was compared among vegetative branches of three plant species with different levels of foliage density: B. dracunculifolia, D. virgatus, and Bidens gardneri. Stalker, and ambusher spiders were more abundant on branches of B. dracunculifolia, which had the highest foliage density. Foliage‐runners constituted the dominant guild on D. virgatus and B. gardneri, which have lower foliage density branches. Our results suggest that branch architecture is the most important factor determining the abundance of plant‐dwelling spiders in the study area independently of branch biomass, leaf surface area or texture.

Efeitos da estrutura da vegetação na composição da assembleia de aranhas (Arachnida: Araneae) em estrato arbóreo de diferentes fitofisionomias do Cerrado

“…Já foi demonstrado que a comunidade de aranhas pode ser alterada pela densidade de folhas nos ramos (Souza & Martins 2005), pela densidade de espinhos e ramos (Gunnarsson 1990, Halaj et al 1998, 2000, morfologia das folhas (Evans 1997), altura e estruturação vertical da planta (Baulfor & Rypstra 1998, Raizer & Amaral 2001.…”

Vertical stratification and effect of petiole and dry leaf size on arthropod feeding guilds in Cecropia pachystachya(Urticaceae)

“…Several studies have shown a positive relationship between the structural complexity of vegetation and diversity of predators (Halaj et al, 2000a, b;Klein et al, 2002;Ribas et al, 2003;Souza 2007;Sanders et al, 2008). Souza and Martins (2005) in a study using artificial branches concluded that the architecture of the branches is the most important factor that determines the abundance of spiders associated with plants. In addition, a recent meta-analysis showed that habitat structure plays an important role in determining the abundance of invertebrate generalist predators (Langellotto and Denno, 2004).…”

Might Heterostyly Underlie Spider Occurrence on Inflorescences? A Case Study ofPalicourea rigida(Rubiaceae), a Common Shrub from Brazilian Cerrado

“…It has been shown, for example, that spider richness and abundance may be influenced by the density of branches [8], leaves [7], and spines [4] by the leaf morphology [9] and by the availability of plant structures distributed vertically [10,11]. Although the patterns between spider diversity and plant architectural complexity have been frequently demonstrated (e.g., [4, 6, 7, Psyche 12]), the causal mechanism which determines these patterns has yet to be identified, and different physical [13] and biotical [5] components of the habitat should be involved.…”

“…Spiders can select substrate based largely on cues from host plant architecture, which may influence the spider assemblage distribution [4,6,7]. It has been shown, for example, that spider richness and abundance may be influenced by the density of branches [8], leaves [7], and spines [4] by the leaf morphology [9] and by the availability of plant structures distributed vertically [10,11].…”