Effects of Natural Enemy Biodiversity on the Suppression of Arthropod Herbivores in Terrestrial Ecosystems

Abstract

Claims about the role of predator diversity in maintaining ecosystem function and providing ecosystem services such as pest control are controversial, but evaluative tests are beginning to accumulate. Empirical and experimental comparisons of species-rich versus species-poor assemblages of entomophagous arthropods and vertebrates range from strong suppression to facilitative release of herbivorous arthropod prey. Top-down control can be strengthened when natural enemies complement each other, dampened by negative interactions, balanced by both factors, and driven by single influential species. A meta-analytic synthesis shows a significant overall effect of enemy richness increasing top-down control of herbivores, which is consistent in agricultural studies conducted in tropical versus temperate zones, in studies using caged versus open-field designs, but not so in nonagricultural habitats. Synthetic analyses address theory and help set precautionary policy for conserving ecological services broadly, while characterizing uncertainty associated with herbivore response to changes in enemy diversity.

Functional traits in agriculture: agrobiodiversity and ecosystem services

“…Root-feeding nematodes (level 3) can suppress N 2 fixation by feeding on roots and decreasing the number of root nodules for N 2 fixation [30]. Similarly, for pest control, consumptive predator activity traits (level 1) affects pest populations (level 2), which in turn affect crop yields (level 3) [61,62]. Thus, it is crucial not only to apply traits to understudied trophic levels, but also to understand the interactions among multiple trophic levels.…”

Intersection between biodiversity conservation, agroecology, and ecosystem services

“…About half the time (45.6%), predator diversity enhanced predation, but predator diversity negatively influenced predation almost as frequently (40.3%), likely due to substitutable effects or interspecific interference. Letourneau et al (2009) reviewed 62 studies, yielding 266 comparisons of diverse versus non-diverse mixtures of natural enemies. Most often (69.5% of comparisons), natural enemy diversity enhanced pest suppression, but sometimes (30% of comparisons), diversity decreased pest suppression.…”

“…For predators, sampling effects may occur where certain species have disproportionately large effects in a community, or where a single species has relatively greater abundance, prey capture ability, longevity, reproductive capacity, or competitive ability (Letourneau et al 2009). In biological control efforts, the sampling effect may be evident with releases of specialist species.…”

Effect of Disease Resistance on Secondary Herbivores: Aphid Abundance on Hybrid and Non-hybrid Coffee Varieties in the Chagga Homegardens

“…It has been suggested that the abundance of natural enemies of herbivores increases with greater crop biodiversity [18]. By extension, higher natural enemy species richness is strongly associated with a reduction in herbivore abundance [19]. Polycultures promote greater diversity and abundance of generalist predators by supporting a greater array of herbivores throughout different stages of the growing season [18].…”