Intraguild predation among aphidophagous predators

Abstract

Abstract. Since the publication of papers by Polis et al. (1989Polis et al. ( , 1992, intraguild predation (IGP) has been considered in numerous systems and a growing number of papers have been published, demonstrating the ubiquity and the importance of this interaction. It appears that aphidophagous guilds constitute especially favourable systems for IGP. Temporal and spatial distributions of aphids promote interactions, such as IGP, among natural enemies. However, despite extensive laboratory and field studies, several questions remain to be answered: Which traits of the different protagonists of the system may promote or hamper the occurrence of IGP? How do ants tending aphids modulate the interaction? How should one consider the "sub-lethal" effects (and the defensive mechanisms) associated with the risk of IGP? May IGP disrupt or enhance aphid control? These different issues are discussed by focusing on the predatory species in the complex system of aphidophagous guilds. It appears that, first, IGP may constitute one of the main forces influencing the structure and dynamics of aphidophagous guilds, and therefore it has to be taken into account in research studies, and second, because of the ephemeral nature of aphid colonies and the great number of species belonging to aphidophagous guilds, understanding all the implications of the interaction, both direct and indirect, constitutes a very complex task.

How functional response and productivity modulate intraguild predation

“…Other studies also reported that additive models for combined predator effects cannot account for non-linearity in combined functional response introduced by behavioral interactions between predators and prey (Soluk 1993; see also Colton 1987 for similar conclusions when one predator interacts with two prey species). However, (1) we estimated behavioral parameters and tested model predictions under similar experimental conditions (e.g., growth chamber, temperature, prey size and age), (2) switching generally occurs when eating the IG prey is risky for the IG predator (Lucas 2005); this is not the case for C. maculata preying on A. aphidimyza larva (Lucas et al 1998), and (3), in another study (A. Sentis, J. L. Hemptinne and J. Brodeur, unpublished manu- v www.esajournals.org script), we investigated the effect of M. persicae density on A. aphidimyza intraguild predation along a temperature gradient and concluded that model predictions were well supported by empirical results. Altogether, this suggests that an insufficient sampling effort probably explains the divergence between model predictions and empirical results at the highest EG prey density.…”

“…However, this might not be the case in other systems where the benefit/cost ratio of eating the IG prey varies. Lucas (2005) proposed four types of IGP: (1) opportunistic, when IGP is a fortuitous event, (2) nutritional, when nutritional benefits are associated with the eating of an IG prey, (3) competitive, when eating the IG prey eliminates an important competitor, and (4) protective, when eating the IG prey eliminates a potential predator under conditions of symmetrical IGP. In the first type, the IG predator does not explicitly search for IG prey, whereas in the three others it actively hunts IG prey because of the benefits of killing or eating them.…”

“…In the first type, the IG predator does not explicitly search for IG prey, whereas in the three others it actively hunts IG prey because of the benefits of killing or eating them. Therefore, the type of IGP, and probably hunting strategy, are described by specific values of search rate (Rosenheim and Corbett 2003, Lucas 2005, Schmitz 2007). Accounting for search rate variations in functional response models would be a promising approach to investigate the effects of IGP type and predator searching behavior on IGP frequency, which may have important repercussions on overall food web dynamics.…”

“…Because most species of predators and parasitoids numerically respond to aphid density and tend to aggregate in densely populated patches (Turchin andKareiva 1989, Chacón andHeimpel 2010), aphids and the guild of their consumers constitute excellent models to explore food web interactions, including IGP, a very common interaction among aphidophagous predators and parasitoids (Brodeur and Rosenheim 2000, Lucas 2005, Gagnon et al 2011. In the present study, under laboratory conditions, we studied interactions between the green peach aphid Myzus persicae Sulzer (Homoptera: Aphididae, the extraguild prey), the spotted ladybeetle Coleomegilla maculata lengi Timberlake (Coleoptera: Coccinellidae, the intraguild predator), and the predatory midge Aphidoletes aphidimyza Rondani (Diptera: Cecidomyiidae, the intraguild prey).…”

“…As Aphidoletes aphidimyza larvae live within the aphid colony and move slowly, we assumed a similar search rate for C. maculata exploiting either intra-or extraguild prey (i.e., a eg ¼ a ig ), a situation corresponding to an opportunistic IGP type (i.e., IGP is a fortuitous event, Lucas 2005). …”