The continuing loss of global biodiversity has triggered questions about the risk that species extinctions pose for the functioning of natural ecosystems and the services they provide for human well-being. There is consensus that on single trophic levels biodiversity sustains functions. However, to understand the full range of biodiversity effects, a holistic and multitrophic perspective is needed. Here we apply methods from ecosystem ecology that quantify trophic network structure and dynamics using ecosystem energetics to data from a large grassland biodiversity experiment. We show that higher plant diversity leads to more energy stored, greater energy flow, and higher community energy-use efficiency across the entire trophic network. These effects of biodiversity on energy dynamics were not restricted to plants only but were also expressed by other trophic groups and to a similar degree in above-and belowground parts of the ecosystem despite plants being by far the dominating group in the system.Positive effects of biodiversity on one trophic level were not counteracted by negative effects on adjacent levels. Trophic levels jointly increased the performance of the community, indicating ecosystem-wide multitrophic complementarity, which is potentially an important prerequisite for the provisioning ecosystem services.

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Fear of predation has been shown to affect prey fitness and behaviour, however, to date little is known about the underlying genetics of responses to predator-associated risk. In an effort to fill this gap we exposed four naïve clones of green peach aphid (Myzus persicae), maintained on the model crop Brassica oleracea, to different types of cues from aphid lion (Chrysoperla carnea). The respective predation risks, we termed Fear Factors, were either lethal (consumption by predator), or non-lethal (non-consumptive predator-associated cues: plant-tethered predator cadavers and homogenised shoot-sprayed or soil-infused blends of predator remains). Our results show that the non-lethal risk cues differentially impeded prey reproductive success that varied by clone, suggesting genotype-specific response to fear of predation. Furthermore, whether plants were perceived as being safe or risky influenced prey responses as avoidance behaviour in prey depended on clone type. Our findings highlight that intra-specific genetic variation underlies prey responses to consumptive and non-consumptive effects of predation. This allows selection to act on anti-predator responses to fear of predation that may ramify and influence higher trophic levels in model agroecosystems.

The dynamics of interactions amongst natural enemies are central to the investigation of insect pest ecology. Ternary and quaternary interactions between parasitoids and predators in the presence of entomophagous organisms are yet to be comprehensively explored. We investigated the performance of a clone of green peach aphid (Myzus persicae (Sulzer); Hemiptera: Aphididae), raised on savoy cabbage (Brassica oleracea Linnaeus; Brassicaceae), under all possible combinations of: I) the parasitoid Aphidius colemani Viereck (Hymenoptera: Braconidae); II) the predator Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae); III) the predator Adalia bipunctata (Linnaeus) (Coleoptera: Coccinellidae); and IV) the spider Parasteatoda tepidariorum (Koch) (Araneae: Theridiidae). We demonstrate a considerably differential green peach aphid abundance, polyphenism, and fine-scale spatial distribution in response to the combination, number, and identity of the present enemy species and their interactions. Surprisingly, certain combinations led to thriving green peach aphid populations due to interference between enemies; whereas, other combinations resulted in tangible collective suppression of the population. At the frontier of agroecology and entomology, we provide fresh insights on the effects of conflict and synergy between natural enemies sharing a pest of a cash crop as prey, highlighting the consequences of the presence of a novel synanthropic spider, as a top predator, on pest regulation.