Arthropod food webs predicted from body size ratios are improved by incorporating prey defensive properties

This dataset was used to run the analyses in the paper "Arthropod food webs predicted from body length ratios are improved by incorporating prey defensive properties" by Van de Walle et al., 2023, Journal of Animal Ecology (in progress). "Arthropod_feeding_trials.csv" contains the results of the experimental feeding trials. Each row contains information on species taxonomy, body size and hunting strategy within a single trial. Abstract Trophic interactions are often deduced from body size differences between predators and potential prey, assuming predators prefer prey smaller than themselves because larger prey are more difficult to subdue. This hypothesis has mainly been confirmed in aquatic ecosystems, but rarely in terrestrial ecosystems, especially in arthropods. Our goal was to validate whether body size ratios can accurately predict trophic interactions in a terrestrial, plant-associated arthropod community. Additionally, we tested whether predator hunting strategy and prey taxonomy could explain possible deviations from this general rule. We collected arthropods from marram grass in coastal dunes and conducted pairwise feeding trials to explicitly test whether two individuals, of the same or different species, would predate each other. From the trial results, we constructed one of the most complete, empirically derived food webs for terrestrial arthropods associated with a single plant species. We contrasted this empirical food web with a theoretical web based on body size ratios, literature and expert knowledge. In our feeding trials, predator-prey interactions were indeed largely size-based. Moreover, the theoretical food web based on body size, activity period, microhabitat and expert knowledge converged quite well with the food web based on experimental feeding trials for both predator and prey species. However, predator hunting strategy, but mainly prey taxonomy improved predictions of predation events. Well-defended taxa, such as hard-bodied beetles, were less frequently consumed than expected based on their body size. Body size ratios predict trophic interactions among plant-associated arthropods fairly well. However, traits such as hunting strategy and anti-predator defences can explain why certain trophic interactions do not adhere to size-based rules. Feeding trials can generate insights into multiple traits underlying real-life trophic interactions among arthropods. Such insights are much needed as the dramatic global decline in arthropod species richness and abundance is knocking out many trophic interactions on which services such as pest control and nutrient cycling depend