Global patterns in the biocontrol efficacy of spiders: A meta‐analysis

Abstract

Aim To investigate the overall effect of spiders on pest suppression and crop performance, and to explore the extent to which the biocontrol efficacy of spiders depends on the characteristics of spiders, pests, agroecosystems, climate and geography. Location Global. Time period 1970–2017. Major taxa studied Spiders. Methods We performed a meta‐analysis of 58 published studies where we investigated (a) the overall effect of spiders on pest density and crop performance; (b) the extent to which the biocontrol efficacy of spiders depends on the taxonomy of pests (aphids, leafhoppers, beetles, and lepidopteran larvae), the hunting strategy of spiders (hunters, web‐weavers), crop type (vine, cabbage, wheat, rice), climate, and geography. Results Spiders suppressed agricultural pest insects in 79% of cases. The mean effect size of increased spider density on pest suppression was large (Hedge's d = 0.89; 95% confidence interval (CI95 )= 0.66–1.12). Spider pest suppression efficacy slightly increased also with taxonomic diversity (d = 0.33; CI95 = 0.05–0.61). The effects of spiders cascaded down and improved crop performance (d = 2.3, CI95 = 0.70–3.84). The effects of spiders seemed to escalate rather than attenuate down through the agricultural food‐chains (regression slopes > 1). The biocontrol efficacy of spiders was highest in rice followed by grape, cabbage and wheat. The pest suppression efficacy of spiders and the positive effect of spiders on crop yield slightly increased towards the tropics and with mean annual temperature. Spiders suppressed the four pest groups with similar efficacy. Main conclusions The meta‐analysis provides strong evidence that spiders are effective in natural pest control and improve crop performance. However, the efficacy of spiders differed among crops. Our study substantiates the few earlier findings that predation pressure and the intensity of trophic cascades in terrestrial ecosystems intensify towards the tropics.

Spatial covariance of herbivorous and predatory guilds of forest canopy arthropods along a latitudinal gradient

“…Michalko et al . (2019) showed an increasing effect of spider density on pest suppression with increasing mean annual temperature, in a meta‐analysis of agro‐ecosystems, but explained the observed patterns as caused by higher prey abundances and the increased strength of top‐down trophic cascades in the tropics. In contrast, Rypstra et al (1986) found an increasing number of spider individuals at lower latitudes and identified the variation in vegetation abundance as the main driver of abundance.…”

Landscape configuration and habitat complexity shape arthropod assemblage in urban parks

“…Ants and beetles comprise a hyperdiverse group of insects and are crucial in an ecosystem 23 because of their different nesting and feeding guilds 24 – 28 . Spiders act as natural enemies and serve as predators’ food in numerous ecosystems 29 – 32 . Approximately 400–800 tons of prey are killed by global spider community every year 33 .…”

Media representation of spiders may exacerbate arachnophobic sentiments by framing a distorted perception of risk

“…Spiders are apical predators in the invertebrate food web (Nyffeler & Birkhofer, 2017), while also representing a fundamental source of food for other organisms, such as birds. The importance of spiders has been even valued in economic terms, given that many species act as major biocontrol for pests in agroecosystem (Cotes et al, 2018;Michalko, Pekar, & Entling, 2019;Michalko, Pekár, Dul'a, & Entling, 2019), and their body structures, silk, and venom are constant sources for bio-inspired materials and engineering solutions (Hinman, Jones, & Lewis, 2000;Heim, Keerl, & Scheibel, 2009;Kang et al, 2014), as well as pharmaceutical products (Saez et al, 2010;Moore, Leung, Norton, & Cochran, 2013). Nevertheless, spiders are still largely underrepresented in global and regional conservation policies, particularly when compared to vertebrates (Leather, 2013;Davies et al, 2018;Fukushima, Mammola, & Cardoso, 2020) or charismatic insects such as butterflies and dragonflies (Milano et al, in prep.).…”