The effects of organic farming on surface-active spider (Araneae) assemblages in wheat in Southern England, UK

Spiders were sampled from organically farmed and conventionally farmed winter wheat fields at three sites in southern England, UK, using pitfall traps. A range of vegetation variables was also recorded from each field. We identified 56 species of spiders from 8609 individuals in our study samples. Most species caught belong to the Linyphiidae, with especially high captures of Oedothorax spp., Erigone spp., Lepthyphantes tenuis (Blackwall 1852), Bathyphantes gracilis (Blackwall 1841) and Meioneta rurestris (C.L. Koch 1836). The Lycosidae were also well represented by Pardosa and Trochosa spp., although the samples were largely dominated by the presence of Pardosa palustris (Linnaeus 1758), More spiders, and more species of spiders, were captured from organic than from conventional fields. Principal Component Analyses suggested that the spider communities differed between the contrasting systems. Our results showed that more spiders, and a greater number of spider species, were captured with increasing abundance of understory vegetation within the crop, both overall and within each farming system.