Spider (Araneae) abundance and diversity across land-use gradients

In agricultural insect pest control, there has been a movement away from broad-spectrum insecticide use towards more sustainable practises. These include lowering pesticide inputs and reducing the harm on beneficial invertebrates, and keeping a more diverse landscape to allow for a more holistic approach to agriculture. Spiders are the dominant and most abundant invertebrate predators in horticultural growing systems. Despite the known potential of spiders as pest reduction ecosystem service providers, they are generally understudied worldwide. We sampled spider populations in economically important kiwifruit orchards that are adjacent to either low-disturbance ecosystems (native forest) or high-disturbance ecosystems (maize), using pitfall traps and active sampling. A total of 2710 spiders were collected from 27 families, representing 64 species and eight functional guilds. The total spider count comprised 2064 (76.2% of total) immature specimens and 646 (23.8% of total) adults. The four most common species (Tenuiphantes tenuis, Erigone prominens, Leucauge dromedaria, Anoteropsis hilaris) accounted for more than half of the adults found (341 of 646 adults). Orb web weavers were the most represented functional group, comprising 45.9% of the total catch. Spider abundance and diversity were higher in kiwifruit crops that were adjacent to maize crops compared with kiwifruit crops adjacent to native forest. There was limited support for a spill-over effect for spiders, indicating low land connectivity. Our findings did not support the Intermediate Disturbance Hypothesis, with the highest abundance and diversity of spiders being observed in the lowest disturbance ecosystem (native forest) rather than the hypothesised intermediate disturbance ecosystem (kiwifruit).