Spatial Scale Modulates the Effect of Habitat Amount on Diversity Patterns of Arachnid Assemblages Across Different Brazilian Ecosystems

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  Spatial Scale Modulates the Effect of Habitat Amount on Diversity Patterns of Arachnid Assemblages Across Different Brazilian Ecosystems ABSTRACT Aim We evaluated how native vegetation cover influences the diversity of arachnid assemblages across multiple spatial scales in major Brazilian ecosystems. Location Brazil (Amazon and Atlantic rainforests, Cerrado savanna and Caatinga dry forest). Taxon Arachnida (Opiliones, Pseudoscorpiones and Scorpiones). Methods We sampled arachnids at 120 sites using active search and litter sifting. Native vegetation cover was quantified at three spatial scales (100, 200 and 300 m buffers) using GIS data. Assemblage structure was assessed using abundance, species richness, and Hill numbers ( q  = 0, 1 and 2). Generalized linear mixed models were used to evaluate responses across taxonomic groups and ecosystems. Results We recorded 3986 individuals from 179 species. Diversity responses to native vegetation cover were taxon-, ecosystem- and scale-de...

Edge Effects and Pitfall Trap Design Influence Spider Diversity and Assemblages in Canola Agroecosystems on the Canadian Prairies

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Edge Effects and Pitfall Trap Design Influence Spider Diversity and Assemblages in Canola Agroecosystems on the Canadian Prairies


ABSTRACT

Spiders (Araneae) are generalist predators in agroecosystems and may contribute to biological control in canola (Brassica napus L. and B. rapa L.). However, their diversity and community structure remain understudied in the Canadian Prairies. To address this knowledge gap, we surveyed spider assemblages in the Aspen Parkland region of Alberta, Canada, using pitfall traps placed at field edges and interiors during the 2021 and 2022 growing seasons. We collected 968 spiders in 74 species across 14 families, with Lycosidae and Linyphiidae being the most abundant. Spider abundance was consistently greater at field edges, although family-level composition varied by year and location. In 2023, we tested pitfall trap modifications to improve spider retention, evaluating (1) trap diameter, (2) preservative substrate (glass beads vs. propylene glycol), and (3) polytetrafluoroethylene (PTFE; Fluon, a non-stick fluoropolymer) coated trap interiors (to reduce friction and prevent escape). This was tested across canola habitats adjacent to grass- or tree-dominated non-crop habitat edges. Trap catches, and resulting richness and diversity, were significantly higher in large PTFE-treated traps, particularly in treed-edge habitats compared to other treatment combinations. These results underscore the importance of non-crop field margins in maintaining spider diversity and highlight design improvements to optimize passive sampling. Our findings provide a regional baseline for spider assemblages in canola systems and offer methodological advances to support future ecological monitoring and conservation biological control efforts in Prairie agroecosystems.

Kent, K., Martínez, A. R., Guelly, K., Pinzon, J., & Mori, B. A. (2025). Edge Effects and Pitfall Trap Design Influence Spider Diversity and Assemblages in Canola Agroecosystems on the Canadian Prairies. Ecology and Evolution, 15(9), e72205. https://doi.org/10.1002/ece3.72205