Predation on sentinel prey increases with increasing latitude in Brassica‐dominated agroecosystems

Abstract

In natural ecosystems, arthropod predation on herbivore prey is higher at lower latitudes, mirroring the latitudinal diversity gradient observed across many taxa. This pattern has not been systematically examined in human‐dominated ecosystems, where frequent disturbances can shift the identity and abundance of local predators, altering predation rates from those observed in natural ecosystems. We investigated how latitude, biogeographical, and local ecological factors influenced arthropod predation in Brassica oleracea‐dominated agroecosystems in 55 plots spread among 5 sites in the United States and 4 sites in Brazil, spanning at least 15° latitude in each country. In both the United States and Brazil, arthropod predator attacks on sentinel model caterpillar prey were highest at the highest latitude studied and declined at lower latitudes. The rate of increased arthropod attacks per degree latitude was higher in the United States and the overall gradient was shifted poleward as compared to Brazil. PiecewiseSEM analysis revealed that aridity mediates the effect of latitude on arthropod predation and largely explains the differences in the intensity of the latitudinal gradient between study countries. Neither predator richness, predator density, nor predator resource availability predicted variation in predator attack rates. Only greater non‐crop plant density drove greater predation rates, though this effect was weaker than the effect of aridity. We conclude that climatic factors rather than ecological community structure shape latitudinal arthropod predation patterns and that high levels of aridity in agroecosystems may dampen the ability of arthropod predators to provide herbivore control services as compared to natural ecosystems.

Predation risk of caterpillar preys in urban agroecosystem is shaped by arthropods and local landscape but not leaf herbivory: a common garden experiment

“…Arthropod predation of herbivore prey is often more prominent in natural environments at lower latitudes (Gray et al 2022), particularly in tropical regions. In an experiment in Subic Bay, Posa et al (2007) showed that arthropod predation was higher in closed canopies.…”

Clay larvae do not accurately measure biogeographic patterns in predation

“…Biased detection should be especially problematic for prey that normally move, such as caterpillars and other larvae. Remarkably few studies have attempted to validate clay larvae against real larvae for comparing predation rates among sites (Greenop et al., 2019; Nagy et al., 2020), even though clay larvae are increasingly used for geographic comparisons (Gray et al., 2022; Roslin et al., 2017; Wallis et al., 2021; Zvereva et al., 2019).…”

Clay larvae do not accurately measure biogeographic patterns in predation

“…Biased detection should be especially problematic for prey that normally move, such as caterpillars and other larvae. Remarkably few studies have attempted to validate clay larvae against real larvae for comparing predation rates among sites (Greenop et al, 2019; Nagy, Schellhorn, & Zalucki, 2020), even though clay larvae are increasingly used for geographic comparisons (Gray et al, 2022; Roslin et al, 2017; Wallis et al, 2021; Zvereva et al, 2019).…”