Super-predation and intraguild interactions in a multi-predator-one-prey system alter the abundance and behaviour of green peach aphid (Hemiptera: Aphididae)

Abstract

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.

Symbiont-conferred immunity interacts with the effects of parasitoid genotype and intraguild predation to shape pea aphid immunity in a clone-specific fashion

“…We purchased 250 mummies of aphids harbouring A. ervi developing juveniles from Koppert UK Ltd. Unlike the non-parasitic males, the females of this solitary koinobiont parasitoid wasp are an efficient natural enemy and biocontrol agent of pea aphids [33,43]. The female oviposits one egg in the viable aphid host.…”

“…The rate of evolution of host resistance to parasitoids, as well as the infectivity (virulence) of parasitoids will be subject to the impacts of internal defensive symbionts [65,72,71] and external factors (e.g. intraguild predators) [32,33]. Altogether, these are constituents of ongoing evolutionary arms-race [31,[37][38][39] that will depend on the levels of variation present in the populations and the associated fitness costs of the involved traits [65,72].…”

“…Most experimental examples of such co-evolutionary arms races [31] have demonstrated these as pairwise interactions between the parasitoid and its host. However, in natural ecosystems, parasitoids do not only operate in such pair-wise interactions as they are themselves interacting with other species that, for example, share aphid populations as prey [32,33]. Therefore, we predict that host and parasite fitness will be significantly affected by the presence of a common enemy such as the aphid lion larva Chrysoperla carnea (Stephens).…”

“…Aphid lions naturally have an advantage over parasitoid wasps. The aphid lion can consume both healthy and parasitised aphids (parasitoid puparia), an ecological process known as intraguild predation (IGP) [33]. This leads to reducing the availability of viable, healthy aphid hosts for the parasitoid and, concomitantly, indirect reduction of parasitoid fitness [33,34].…”

“…The aphid lion can consume both healthy and parasitised aphids (parasitoid puparia), an ecological process known as intraguild predation (IGP) [33]. This leads to reducing the availability of viable, healthy aphid hosts for the parasitoid and, concomitantly, indirect reduction of parasitoid fitness [33,34]. In response to parasitoidism, aphids are known to exhibit altruistic risk-taking behaviour by exposure to predators when parasitised, thus, in essence, sacrificing the diseased few for the benefit of the genetically identical population (clone) [35,36].…”