Spider venom potency exhibits phylogenetic prey-specificity but does not trade-off with body size or silk use in prey capture

Spiders employ a diverse range of predator traits including potent venoms, complex silk hunting strategies and mechanical strength coupled with larger body sizes to capture prey. This trait diversity, along with the quantifiable nature of venom potency, makes spiders an excellent group to study evolutionary trade-offs. Yet, comparative approaches have been historically confounded by the use of atypical prey models to measure venom potency. Here, we account for such confounding issues by incorporating the phylogenetic similarity between a spider's diet and the species used to measure its venom potency. Using a phylogenetic comparative analysis of 75 spider species to test how diet, silk use in prey capture and body size drive venom yield and potency (LD50), we show that spider venoms are generally more potent against models more closely related to their natural prey, reflecting prey-specific patterns. We find that venom yield scales sublinearly with size, reflecting the 0.75 allometric scaling predicted by metabolic theory, suggesting venom is metabolically expensive in spiders. Our approach demonstrates how contemporary comparative approaches can be applied to historic venom potency measures to test fundamental evolutionary patterns in predator traits.

Methods
To test our hypotheses, we collated data on venom potency, body size, silk use in prey capture (yes/no), venom yield, LD50 model species and natural diet from literature sources using the Web of Science search engine using the key words “LD50” “Venom”, “Spider” “Arachnid” “Yield” and following key references and databases such as The World Spider Trait database. All data was stored and organised in Microsoft Excel (S1-S2).

The data has been processed prior to analysis. See Supplementary document S6 for a detailed description of both the methodology used and data descriptions, in the form of column heading descriptions for both dataset files, S1 (Main dataset) and S2 (length to mass conversion data).

To reproduce the results and phylogeny, see S3 and S4 (knowledge of R coding language required). To see full model outputs (results) in the form of tables and figures, see S5.

To recap: S1 and S2 are the datasets, S1 being the main dataset and S2 being separate data used to convert spider body size to spider body mass; S3 is the R script to reproduce the results; S4 is the R script and files required to reproduce the phylogeny; S5 is a word document containing all analyses outputs (results) for both main and supplementary analyses; and S6 is a word document explaining the methodology used in greater detail and data descriptions.