Spiders as key predators of aquatic prey

In this blogpost, Eric and his research group explore the key role of spiders in riparian ecosystems. Analyzing a substantial stable isotope dataset, this study uncovers nuanced patterns of aquatic insect consumption by spiders, considering hunting modes, habitat specializations and seasonal variations. 

“Our study delves into the dietary habits of spiders within riparian zones, shedding light on their consumption of aquatic insects and the factors influencing these patterns. With a comprehensive stable isotope dataset, we explore the dynamics across six spider species (Figure 1), representing different hunting modes and habitat specializations. The study reveals that specialists do not consistently feed more on aquatic prey than their generalist counterparts. Noteworthy findings include the varied proportions of aquatic sources in spiders’ diets, ranging from 17% to 99%, with web builders exhibiting the highest proportion at 78%. Seasonal variations play a crucial role, with the highest consumption of aquatic prey observed in June and August.

The plot (Figure 2) shows 50% (light), 75% (medium) and 95% (dark) highest density intervals of the posterior distribution of aquatic proportion to spiders’ diet. Black lines show the maximum a posteriori probability and white dots the median of the posterior distribution. The seasonal data is shown for ground hunters, web builders, and vegetation hunters in the riparian system adjacent to the pond and the stream. For each feeding type, one species is considered a wetland specialist (ie,  Tetragnatha extensa, Pirata piraticus , and  Dolomedes fimbriatus ) while the other is considered a habitat generalist (ie,  Tetragnatha montana, Pardosa amentata , and  Pisaura mirabilis ). If the model could not be fitted, no crossbar is shown.

Intriguingly, web builders almost exclusively rely on aquatic sources during this period. Furthermore, elemental analysisindicate an accumulation of lipids in October, suggestingthat high-quality lipids of aquatic origin may also play a critical role during winter. Ultimately, the study underscores the importance of aquatic prey for spiders, emphasizing the nuanced interplay between hunting modes, seasons and the sustenance of spider populations in riparian ecosystems.”

The publication titled ‘The influence of season, hunting mode, and habitat specialization on riparian spiders as key predators in the aquatic-terrestrial linkage’ was authored by Eric Bollinger, Jochen P. Zubrod, Dominic Englert, Nadin Graf, Oliver Weisner, Sebastian Kolb, Ralf B. Schäfer, Martin H. Entling & Ralf Schulz