Mechanisms Underlying the Nonconsumptive Effects of Parasitoid Wasps on Aphids

Abstract

Natural enemies need not consume herbivores to suppress herbivore populations. Behavioral interactions can adversely impact herbivore fitness from reduced time feeding, investment in defense, or injury from failed attacks. The importance of such "nonconsumptive effects" for herbivore suppression may vary across species based on the specificity and intensity of the herbivore defensive response. In a series of manipulative studies, we quantified the nature and consequences of nonconsumptive interactions between two parasitoid wasps, Aphidius ervi Haliday and Aphidius colemani Viereck, on two aphid species, pea aphids (Acyrthosiphon pisum (Harris)) and green peach aphids (Myzus persicae (Sulzer)). Both wasps successfully parasitize green peach aphids, but only A. ervi parasitizes pea aphids. We observed A. ervi antennating and stinging pea aphids and documented a decrease in pea aphid longevity in response to stinging even when the aphid survived the interaction and no mummy formed. The primary defensive tactic of pea aphids in response to either wasp species was dropping from the host plant. Both wasp species antennated and stung green peach aphids, but they elicited unique defensive behaviors. Green peach aphids kicked or emitted cornicle secretions in response to A. colemani but spent more time off the plant in the presence of A. ervi. Green peach aphid longevity and fecundity were not affected by wasp stings when the aphid survived and no mummy formed. Our study demonstrates the complexity of behavioral interactions between parasitoids and their potential hosts and contributes to a mechanistic understanding of variation in the nonconsumptive suppression of herbivore populations.

Species interactions affect the spread of vector‐borne plant pathogens independent of transmission mode

“…We assumed predators and competitors decrease vector fitness by reducing vector fecundity and/or increasing mortality (Awmack andLeather 2002, Finke 2012), while mutualists increase it (Rice and Eubanks 2013). We assumed that all interaction types may have positive, negative, or neutral effects on vector movement, given that empirical studies have documented such variable effects (Roitberg et al 1979, Denno et al 2003, Nelson and Rosenheim 2006, Styrsky and Eubanks 2007, Mgochecki and Addison 2010, Kersch-Becker and Thaler 2015, Long and Finke 2015, Ingerslew and Finke 2017. Our model examined "nonpersistent" and "persistent" transmission modes.…”

Dropping to escape: a review of an under‐appreciated antipredator defence

“…Even where aphids at any life stage are successful in locating a new plant on which to feed after dropping, their lifetime fecundity is likely to be impaired due to the loss of feeding time and energy expended in searching (Roitberg, Myers & Frazer, ; Nelson, ). By reducing fecundity, this key ‘non‐consumptive effect’ of predators – and parasitoids (Fill, Long & Finke, ; Ingerslew & Finke, ) – can substantially reduce prey population growth (Nelson, Matthews & Rosenheim, ; Nelson & Rosenheim, ; Nelson, ).…”

Live and inanimate predator-associated cues suppress the population of sap-feeding prey and induce polyphenism

“…Also, prey reproductive success may undergo inhibition, or reproduction may be altered under intimidation by predators (Preisser et al ., 2005; McCauley et al ., 2011), alarm pheromone effects (de Vos et al ., 2010), and behavioural changes (Nelson et al ., 2004; Hoki et al ., 2014). Whichever choice the prey make, the decision of developing anti-predator responses and reacting to environmental risks incur an ecological cost (Agabiti et al ., 2016; Ingerslew and Finke, 2017; Hermann and Landis, 2017), leading in general to compromised prey fitness and temporarily altered dynamics and behaviours (Lima and Dill, 1990; Sih, 1994; Sih, 1997; Nelson et al ., 2004; Preisser et al ., 2005) to the advantage of survival (Francke et al ., 2008; Keiser, 2012).…”

“…The effects triggered by predator cues (Norin, 2009) diffuse through prey population and intensify in effect due to aphid pheromone communication (de Vos et al ., 2010; Keiser, 2012, Ingerslew and Finke, 2017), thereby inducing varied responses such as polyphenism (Weisser et al ., 1999), and/or changes in reproductive success (Khudr et al ., 2017). In this regard, using isolated predators or inanimate objects cued by predator info-chemicals as a form of risk to affect parthenogenetic phloem-feeding insects has not received enough attention compared to the effects of the deployment of impaired predators (Nelson et al ., 2004; Nelson and Rosenheim, 2006).…”

“…Indeed, treating aphid/pest environment, including host plants, predator decoys and soil, with suspensions bearing predator-borne info-chemicals may break new ground in pest control. Moreover, while most research on the ecology of fear focuses on prey performance changes, following behaviour modifications, there is an emergent need to decipher previously uncharted non-consumptive effects on prey fitness and pest control where innovative ecological means are employed (Ingerslew and Finke, 2017).…”