Abstract
Intraguild predation (IGP) takes place when natural enemies that use similar resources attack each other. The impact of IGP on biological control can be significant if the survival of natural enemy species is disrupted. In the present study, we assessed whether Geocoris punctipes (Hemiptera: Lygaeidae) engages in IGP on Eretmocerus eremicus (Hymenoptera: Aphelinidae) while developing on whitefly nymphs of Trialeurodes vaporariorum (Hemiptera: Aleyrodidae). In choice and non-choice tests, we exposed G. punctipes to parasitized and non-parasitized whitefly nymphs. We found that G. punctipes does practice IGP on E. eremicus. However, choice tests assessing G. punctipes consumption revealed a significant preference for non-parasitized T. vaporariorum nymphs. Subsequently, we investigated whether E. eremicus females modify their foraging behavior when exposed to conditions involving IGP risk. To assess this, we analyzed wasp foraging behavior under the following treatments: i) whitefly nymphs only (control = C), ii) whitefly nymphs previously exposed to a predator ( = PEP) and, iii) whitefly nymphs and presence of a predator ( = PP). In non-choice tests we found that E. eremicus did not significantly modify its number of attacks, attack duration, oviposition duration, or behavior sequences. However, E. eremicus oviposited significantly more eggs in the PEP treatment. In the PP treatment, G. punctipes also preyed upon adult E. eremicus wasps, significantly reducing their number of ovipositions and residence time. When the wasps were studied under choice tests, in which they were exposed simultaneously to all three treatments, the number of attacks and frequency of selection were similar under all treatments. These results indicate that under IGP risk, E. eremicus maintains several behavioral traits, but can also increase its number of ovipositions in the presence of IG-predator cues. We discuss these findings in the context of population dynamics and biological control.
Highlights
A ‘guild’ is described as all taxa in a community that use similar resources and can compete [1]
We found that G. punctipes readily preys upon parasitized and non-parasitized T. vaporariorum nymphs
We found that G. punctipes significantly prefers to prey on non-parasitized nymphs of T. vaporariorum relative to parasitized nymphs when predators were confronted with both nymph forms in a choice arena (t = 2.98, df = 24.58, P = 0.0064)
Summary
A ‘guild’ is described as all taxa in a community that use similar resources (food or space) and can compete [1]. Intraguild predation (IGP), in turn, can be understood as attack among natural enemies that use similar resources [2]. IGP can be reciprocal (when both natural enemies attack each other) or asymmetric (when only one species attacks the other). It is generally accepted that IGP is ubiquitous in nature, and several cases have been reported among terrestrial heteropteran predators [3,4] and aleurophagous predators [5,6]. IGP is commonly asymmetric, with the parasitoid the hunted natural enemy (IG-prey) and the predator, the ‘true’ predator (IGpredator) that preys on the parasitoid [7,8,9,10,11,12]. IGP can be a disruptive or a stabilizing force at the population or community levels [1]
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