Survival of a specialist natural enemy experiencing resource competition with an omnivorous predator when sharing the invasive prey Tuta absoluta.

Anaïs Chailleux,Philippe Bearez,Nicolas Desneux,Anthony Droui

doi:10.1002/ece3.3396

Abstract

Can specialist natural enemies persist in ecosystems when competing with omnivorous natural enemies for their shared prey? The consequences of omnivory have been studied theoretically, but empirical studies are still lacking. Omnivory is nevertheless common in nature and omnivorous predators coexist with specialists in many ecosystems, even when they are intraguild predators. This type of association is also common in agroecosystems in which biological control strategies are used. Our study provides an example of the outcome of such an association in the context of biological control of the invasive pest Tuta absoluta (Lepidoptera) in a tomato agroecosystem. The two natural enemies involved, that is, a specialist (Stenomesius japonicus (Hymenoptera) parasitoid) and an omnivore (Macrolophus pygmaeus (Hemiptera) predator), were able to coexist for 3 months in our experimental cages in the absence of metacommunity mechanisms (i.e., emigration and recolonization), contrary to theoretical expectations. However, they negatively affected each other's population dynamics. We found that spatial resource segregation was not a mechanism that promoted their coexistence. Regarding pest control, the specialist and omnivorous natural enemies were found to exhibit complementary functional traits, leading to the best control when together. Mechanisms that may have promoted the coexistence of the two species as well as consequences with regard to the inoculative biological control program are discussed.

Highlights

Multiple natural enemy species commonly attack single prey/host species (Hawkins, 1990; Hawkins & Mills, 1996; Polis, 1991; Polis & Strong, 1996; Price, 1971)
The objectives of this study were (i) to quantify the outcome of a frequent species association with an ecosystem, both feeding on the same prey, and (ii) to identify resource utilization patterns that could promote the coexistence of the two natural enemies
The results showed that coexistence was possible between the two natural enemy species, despite the asymmetry in their diet breadth and the occurrence of kleptoparasitism (Chailleux, Wajnberg et al, 2014): S. japonicus and M. pygmaeus became successfully established in all treatments in which they were released and were present throughout the duration of the experiment

Summary

Introduction

Multiple natural enemy species commonly attack single prey/host species (Hawkins, 1990; Hawkins & Mills, 1996; Polis, 1991; Polis & Strong, 1996; Price, 1971). How do they coexist in ecosystems when tapping a common resource is a key question to address in order to understand ecosystem functioning Especially regarding studies on the effects of true omnivory, that is, feeding on different trophic levels, such as on plants and on herbivores, and on different herbivore prey species (Coll & Guershon, 2002; Pimm & Lawton, 1978)

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Conclusion