Environmental and spatial drivers of spider diversity at contrasting microhabitats

Abstract

The relative importance of environmental and spatial drivers of animal diversity varies across scales, but identifying these scales can be difficult if a sampling design does not match the scale of the target organisms' interaction with their habitat. In this study, we quantify and compare the effects of environmental variation and spatial proximity on ground-dwelling spider assemblages sampled from three distinct microhabitat types (open grassland, logs, trees) that recur across structurally heterogeneous grassy woodlands. We used model selection and multivariate procedures to compare the effects of different environmental attributes and spatial proximity on spider assemblages at each microhabitat type. We found that species richness and assemblage composition differed among microhabitat types. Bare ground cover had a negative effect on spider richness under trees, but a positive effect on spider richness in open grassland. Turnover in spider assemblages from open grassland was correlated with environmental distance, but not geographic distance. By contrast, turnover in spiders at logs and trees was correlated with geographic distance, but not environmental distance. Our study suggests that spider assemblages from widespread and connected open grassland habitat were more affected by environmental than spatial gradients, whereas spiders at log and tree habitats were more affected by spatial distance among these discrete but recurring microhabitats. Deliberate selection and sampling of small-scale habitat features can provide robust information about the drivers of arthropod diversity and turnover in landscapes.

Foraging by an avian ecosystem engineer extensively modifies the litter and soil layer in forest ecosystems

“…Lyrebird foraging increases the local diversity of microhabitats available to the invertebrate fauna by creating a complex mosaic of recently raked patches of exposed soil adjoining finely mixed litter and mineral soil ejecta, embedded in a matrix of an undisturbed litter layer. Together with changes arising from the mixing of litter and soil (greater aeration, surface contact between litter and mineral soil, altered decomposition rates), the composition and abundance of invertebrate communities are likely to be altered across large spatial scales (García‐Palacios et al 2013, Barton et al 2017).…”

Islands in the trees: A biogeographic exploration of epiphyte‐dwelling spiders

“…In accordance with the ETIB, larger epiphytes have been found to host a greater number of arthropod species such as ants, beetles, springtails, and spiders (Méndez‐Castro & Rao, ; Rodgers & Kitching, ; Stuntz, Ziegler, Simon, & Zotz, ; Wardle et al., ). However, the effect of isolation on faunal diversity is difficult to demonstrate (Barton, Evans, Foster, Cunningham, & Manning, ; Jiménez‐Valverde, Baselga, Melic, & Txasko, ; Wu, Si, Didham, Ge, & Ding, ). So far, isolation effects (interisland distance) on canopy fauna have been studied only once, for canopy soil communities in real and artificial soil accumulations in New Zealand, where no significant effects were detected (Wardle et al., ).…”

“…Spiders are highly sensitive to subtle changes in habitat structure (Gonçalves‐Souza et al., ) and microclimatic conditions and they show active habitat selection (Omena & Romero, ; Rao, ). Because of this sensitivity, habitat diversity is expected to positively affect spider species numbers even at small spatial scales (Aikens & Buddle, ; Barton et al., ; De Mas, Chust, Pretus, & Ribera, ). On top of being selective and sensitive towards the physical structure of their habitat, spiders display a variety of foraging strategies and can be classified into functional guilds (Cardoso, Pekár, Jocqué, & Coddington, ), which differ in their mobility (e.g., web builders vs. active hunters).…”

Tree species and microhabitat affect forest bog spider fauna

“…Ground-dwelling spiders are mostly comprised of cursorial species that wander across diverse microhabitats in search of their prey. Whereas vegetation-dweller species, either web-builders or active hunters are more dependent on habitat structures that are necessary for web placement or constitute the substrate for foraging (Barton et al 2017;Gollan et al 2010).…”