Local-scale determinants of arboreal spider beta diversity in a temperate forest: roles of tree architecture, spatial distance, and dispersal capacity

Abstract

Spiders are a functionally important taxon in forest ecosystems, but the determinants of arboreal spider beta diversity are poorly understood at the local scale. We examined spider assemblages in 324 European beech (Fagus sylvatica) trees of varying sizes across three forest stands in Würzburg (Germany) to disentangle the roles of tree architecture, spatial distance, and dispersal capacity on spider turnover across individual trees. A large proportion of tree pairs (66%) showed higher compositional dissimilarity in spider assemblages than expected by chance, suggesting prominent roles of habitat specialization and/or dispersal limitation. Trees with higher dissimilarity in DBH and canopy volume, and to a lesser extent in foliage cover, supported more dissimilar spider assemblages, suggesting that tree architecture comprised a relevant environmental gradient of sorting spider species. Variation partitioning revealed that 28.4% of the variation in beta diversity was jointly explained by tree architecture, spatial distance (measured by principal coordinates of neighbor matrices) and dispersal capacity (quantified by ballooning propensity). Among these, dispersal capacity accounted for a comparable proportion as spatial distance did (6.8% vs. 5.9%). Beta diversity did not significantly differ between high- and low-vagility groups, but beta diversity in species with high vagility was more strongly determined by spatially structured environmental variation. Altogether, both niche specialization, along the environmental gradient defined by tree architecture, and dispersal limitation are responsible for structuring arboreal spider assemblages. High dispersal capacity of spiders appears to reinforce the role of niche-related processes.

Plant-dwelling spider communities of three developmental phases in primeval oak-lime-hornbeam forest in the Białowieża National Park, Poland

“…Gómez et al (2016) showed that the density of spiders building aerial webs increases with increasing vegetation height and the number of vegetation layers. Zhang et al (2018) showed that spider communities living on the European beech Fagus sylvatica are significantly affected by such parameters of trees as trunk diameter at breast height, canopy volume, and foliage cover.…”

Spider Assemblages of Tree Branches in Managed and Primeval Deciduous Stands of the Białowieża Forest

“…Porrhomma pygmaeum was the most abundant spider species in both alder carr plots (Table 1). The lowest number of species was found in the managed oak-lime-hornbeam forest (11) and the highest in primeval alder carr (23 species). However, the calculated estimators indicated higher species richness (varying depending on the estimator), especially for primeval alder carr, for which the sampling completeness was the lowest, at 53%, whereas in the other plots sampling completeness was about 70-80% (Table 2).…”

“…Therefore, the collected material derives not only from the foliage growing out of thin branches but also from tree trunks. As a result, spiders from these two microhabitats have previously been analyzed as one group [9][10][11], which might have led to incorrect conclusions as these two habitats are markedly different in terms of microhabitat structure and microclimatic conditions, and thus spider assemblages inhabiting them are likely to be different [12,13].…”

Drivers of the beta diversity of spider assemblages in southern Brazilian temporary wetlands

“…geographic distances; spatial eigenvectors) (Carvalho et al ., ). In relation to spider metacommunity structure, most studies found that species‐sorting assembly processes predominate over dispersal limitation to spider metacommunity structure, as most studies detected a higher relative importance of environmental over spatial predictors in explaining the variation in spider composition across a diverse array of environments, including dunes, forests and grasslands (Baldissera et al ., , ; Jiménez‐Valverde & Lobo, ; Jiménez‐Valverde et al ., ; Carvalho et al, 2012a, 2012b; Rodriguez‐Artigas et al ., ; Tonkin et al ., ; Zhang et al ., ). In fact, many authors have found weaker influence of geographic distances on spider assemblage composition compared with environmental predictors (Jiménez‐Valverde et al ., ; Carvalho et al ., ).…”

“…Thus, several studies investigating the relative importance of environmental drivers and spatial predictors have been conducted recently. In general, most studies have detected a prevailing importance of environmental over spatial predictors, suggesting that spider assemblages are mostly structured by species sorting (Baldissera et al ., ; Carvalho et al ., ; Rodriguez‐Artigas et al ., ; Zhang et al ., ), although the contribution of environmental drivers seems to change with the spatial extent of a study (Carvalho et al ., ).…”