Herbivore population suppression by an intermediate predator, Phytoseiulus macropilis, is insensitive to the presence of an intraguild predator: an advantage of small body size?

Abstract

Recent work in terrestrial communities has highlighted a new question: what makes a predator act as a consumer of herbivores versus acting as a consumer of other predators? Here we test three predictions from a model (Rosenheim and Corbett in Ecology 84:2538-2548) that links predator foraging behavior with predator ecology: (1) widely foraging predators have the potential to suppress populations of sedentary herbivores; (2) sit and wait predators are unlikely to suppress populations of sedentary herbivores; and (3) sit and wait predators may act as top predators, suppressing populations of widely foraging intermediate predators and thereby releasing sedentary herbivore populations from control. Manipulative field experiments conducted with the arthropod community found on papaya, Carica papaya, provided support for the first two predictions: (1) the widely foraging predatory mite Phytoseiulus macropilis strongly suppressed populations of a sedentary herbivore, the spider mite Tetranychus cinnabarinus, whereas (2) the tangle-web spider Nesticodes rufipes, a classic sit and wait predator, failed to suppress Tetranychus population growth rates. However, our experiments provided no support for the third hypothesis; the sit and wait predator Nesticodes did not disrupt the suppression of Tetranychus populations by Phytoseiulus. This contrasts with an earlier study that demonstrated that Nesticodes can disrupt control of Tetranychus generated by another widely foraging predator, Stethorus siphonulus. Behavioral observations suggested a simple explanation for the differing sensitivity of Phytoseiulus and Stethorus to Nesticodes predation. Phytoseiulus is a much smaller predator than Stethorus, has a lower rate of prey consumption, and thus has a much smaller requirement to forage across the leaf surface for prey, thereby reducing its probability of encountering Nesticodes webs. Small body size may be a general means by which widely foraging intermediate predators can ameliorate their risk of predation by sit and wait top predators. This effect may partially or fully offset the general expectation from size-structured trophic interactions that smaller predators are subject to more intense intraguild predation.

Functional diversity positively affects prey suppression by invertebrate predators: a meta‐analysis

“…1998, Rosenheim et al. 2004b). Additionally, body size ratios between predators and prey have been shown to affect consumption rates (Lucas et al.…”

“…Similarly, size differences between predators and prey can also influence intraguild interactions and play an important role in predicting consumption rates (Rosenheim et al. 2004b, Brose et al. 2008, Ball et al.…”

Linking a Predator's Foraging Behavior With Its Effects on Herbivore Population Suppression

“…Thus, we expected to see residual positive effects of Nesticodes on spider mites in the ϪStethorus treatments, and these indeed were observed, making it difficult to detect a significant spiders ϫ Stethorus interaction. (4) Two additional experiments conducted later in the spring, when Phytoseiulus had replaced Stethorus as the dominant predator of spider mites, demonstrated that spiders no longer accelerate spider mite population growth rates (Rosenheim et al 2004). 2B, 3B).…”

The effects of attacks by the mutualistic ant, Lasius japonicus Santschi (Hymenoptera: Formicidae) on the foraging behavior of the two aphidophagous ladybirds, Coccinella septempunctata brucki Mulsant (Coleoptera: Coccinellidae) and Propylea japonica (Thunberg) (Coleoptera: Coccinellidae)

“…The Effects of Ant Attacks on Ladybirds 165 studies show that increased food requirement is known to lead to strong interactions between individuals involved in such interactions (Yasuda and Kimura, 2001;Yasuda et al, , 2004Rosenheim et al, 2004). For instance, in an arthropod predatory community the predatory mite, Phytoseiulus macropilis (Banks), whose food requirement is small, has less probability of encountering their higher-order predator than the predatory beetle, Stethorus siphonulus Kapur, which has a large food requirement (Rosenheim et al, 2004).…”

“…For instance, in an arthropod predatory community the predatory mite, Phytoseiulus macropilis (Banks), whose food requirement is small, has less probability of encountering their higher-order predator than the predatory beetle, Stethorus siphonulus Kapur, which has a large food requirement (Rosenheim et al, 2004). Therefore, the food requirement of ladybirds would be one of the important factors in understanding the strength of interactions between ladybirds and mutualistic ants.…”