Resilience of riparian spiders to floods: evidence from a mesocosm study
Abstract
- Floods are key hydrological events that shape river and riparian ecosystems, promoting bidirectional exchanges of material and organisms. However, anthropogenic activities have altered natural flood dynamics, reducing flood frequency and leading to generalist species becoming more dominant in riparian communities. Climate change, in contrast, may increase extreme precipitation and flooding frequency, negatively impacting generalists not adapted to flooding.
- Riparian spiders are key predators that contribute to ecosystem stability by controlling insect populations. However, it remains unclear how altered flooding regimes affect riparian spider communities. To address this, we conducted a mesocosm experiment using 16 artificial streams, exposing riparian spider communities to one of four flooding durations (i.e., 0, 3, 7 and 14 days). The floods inundated the streams' riparian area twice, once in May and once in June; spiders were sampled before and after each flood.
- While spider abundance was not affected, species richness decreased by 30% after the first 14-day-lasting flood. The second 14-day-lasting flood, however, increased spider abundance and species richness by 73% and 43% compared to the control and before the flood, respectively. Wetland specialists Piratula latitans and Pirata piraticus were five and three times more abundant in flooded areas, while generalists Pardosa hortensis and Pardosa palustris were only found in control areas.
- Despite being dominated by generalists, riparian spider communities demonstrated high resilience to floods. Re-exposing riparian habitats to flooding may not threaten these communities but rather enhance biodiversity by promoting a shift towards more typical riparian arthropods, supporting flood regime restoration for conservation.
Mutel, S., Entling, M. H., Breithaupt, C., Burgazzi, G., Fiolka, F., Middendorf, F., Ogbeide, C., Bundschuh, M., Schulz, R., & Manfrin, A. Resilience of riparian spiders to floods: Evidence from a mesocosm study. Insect Conservation and Diversity. https://doi.org/10.1111/icad.70040