The distribution, spatial clustering, and density of trapdoor spiders in two California coastal dune ecosystems

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  The distribution, spatial clustering, and density of trapdoor spiders in two California coastal dune ecosystems Abstract Coastal dune ecosystems support endemic trapdoor spiders, yet population data for these species are limited. We conducted the first coastal dune trapdoor spider population estimation surveys at Moss Landing State Beach (California) and for Aptostichus stephencolberti Bond 2008 at Sunset State Beach using randomly selected 1m 2 quadrats across ~26,000 m 2 per site. Burrow densities were similar between sites (Sunset: 0.287 burrows/m 2 ; Moss: 0.453 burrows/m 2 ), yielding estimated population sizes of ~35,206 and ~30,959 individuals, respectively. However, spatial analyses revealed contrasting patterns of burrow distribution. At Sunset State Beach, burrow presence was strongly associated with vegetation and occurred closer to plants, despite vegetation being randomly distributed. In contrast, no vegetation–burrow association was detected at Moss Landing, alth...

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

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

Abstract

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. Despite predictions, we find no trade-offs among body size, silk use and venom potency. We find that venom yield scales sublinearly with size, reflecting the 0.75 allometric scaling predicted by metabolic theory, suggesting that 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.

Lyons Keith, Dugon M. M. and Healy Kevin 2025Spider venom potency exhibits phylogenetic prey specificity but does not trade-off with body size or silk use in prey captureBiol. Lett.2120250133 http://doi.org/10.1098/rsbl.2025.0133