Understanding the impact of flooding on trait‐displacements and shifts in assemblage structure of predatory arthropods on river banks

Abstract

Summary1. Species assemblages of naturally disturbed habitats are governed by the prevailing disturbance regime. Consequently, stochastic flood events affect river banks and the inhabiting biota. Predatory arthropods occupy predominantly river banks in relation to specific habitat conditions. Therefore, species sorting and stochastic processes as induced by flooding are supposed to play important roles in structuring riparian arthropod assemblages in relation to their habitat preference and dispersal ability. 2. To ascertain whether assemblages of spiders and carabid beetles from disturbed river banks are structured by stochastic or sorting mechanisms, diversity patterns and assemblage-wide traitdisplacements were assessed based on pitfall sampling data. We tested if flooding disturbance within a lowland river reach affects diversity patterns and trait distribution in both groups. 3. Whereas the number of riparian spider species decreased considerably with increased flooding, carabid beetle diversity benefited from intermediate degrees of flooding. Moreover, regression analyses revealed trait-displacements, reflecting sorting mechanisms particularly for spiders. Increased flooding disturbance was associated with assemblage-wide increases of niche breadth, shading and hygrophilic preference and ballooning propensity for spider (sub)families. Trait patterns were comparable for Bembidiini carabids, but were less univocal for Pterostichini species. Body size decreased for lycosid spiders and Bembidiini carabids with increased flooding, but increased in linyphiid spiders and Pterostichini carabids. 4. Our results indicate that mainly riparian species are disfavoured by either too high or too low degrees of disturbance, whereas eurytopic species benefit from increased flooding. Anthropogenic alterations of flooding disturbance constrain the distribution of common hygrophilous species and/ or species with high dispersal ability, inducing shifts towards less specialized arthropod assemblages. River banks with divergent degrees of flooding impact should be maintained throughout dynamic lowland river reaches in order to preserve typical riparian arthropod assemblages.

Toward the use of testate amoeba functional traits as indicator of floodplain restoration success

“…grazing pressure in the pasture, waterlogging in the Willow forest). Flood-related effects on biotic communities are well-known for higher plants [48] and animals [49,50], but our result tend to show that filters are different for protists than for plants and arthropods. Defining and testing the effects of these filters will improve our understanding of soil microbial ecology and requires further studies ideally combining descriptive approaches such as used here (to confirm the observed pattern for TA and/or other soil organisms) and manipulative experiments (to test the effect of specific factors).…”

Spider assemblages and dynamics on a seasonal island in the Pripyat River, Belarus

“…they serve as refuges for the invertebrate fauna. The life-history traits of the spider species such as active hunting and air, ground, and water surface dispersal capacity enable spiders to settle in a newly emerged territory (Richter, 1970a;Richter et al, 1971;Lambeets et al, 2008Lambeets et al, , 2009Pétillon et al, 2010).…”

“…Lowering of the water level had a major influence on the increasing spider species diversity on the seasonal island. Lambeets et al (2008Lambeets et al ( , 2009) revealed that diverse groups of arthropods (carabids and spiders) can respond differently to a flood disturbance. Intermediate flooding increased the number of carabid species, while in the case of riparian spiders, rising water levels decreased their species richness.…”

Effect of the colour of pitfall traps on their capture efficiency of carabid beetles (Coleoptera: Carabidae), spiders (Araneae) and other arthropods

“…Kratochwil & Schwabe, 2001;Lambeets et al, 2008Lambeets et al, , 2009Negro et al, 2009), were most frequently caught in white and yellow coloured traps. Thus, carabid beetles and spiders in open habitats seem to be attracted by bright colours, maybe due to the sharp contrast between the trap and surrounding vegetation/ground and between the trap and possible prey (shown for Cicindelidae by Faasch, 1968;Gebert, 1991).…”