Active prey mixing as an explanation for polyphagy in predatory arthropods: synergistic dietary effects on egg production despite a behavioural cost

Abstract

Summary Mixing of prey that differ in nutrient content or toxic compounds (dietary mixing) may allow synovigenic predatory arthropods to balance their diet or dilute toxins of different prey items to maximize performance: dietary mixing may therefore explain the prevalence of polyphagy in this functional group. Several predatory arthropods can redress nutritional imbalances in their diet by actively mixing different diets, based on experiments with artificial diets or with prey that were manipulated to contain different nutrients. Evidence is also accumulating that predator species perform better on a mixed diet of several different prey species, but evidence that they actively forage for different prey species is scarce. Thus, evidence that predators actively forage for a mixed diet consisting of natural, non‐manipulated prey to increase their performance is still rare. Here, we investigate whether arthropod predators invest in achieving an optimal diet by active mixing of different prey species or by simply eating what they encounter. Females of two species of plant‐inhabiting predatory mites produced significantly more eggs when feeding on a prey mixture of co‐occurring phytophagous mites than when feeding on either of the two prey species separately. When the two prey species were offered on two separate, connected patches at some distance from each other, predators commuted significantly more between the two patches to obtain a mixed diet and had a significantly increased egg production than predators that were offered a single prey species on two patches. Thus, predators actively commuted between patches to balance their diet. We propose that active dietary mixing can have synergistic effects on predator fitness and has the potential to explain polyphagy in this functional group.

Predatory interactions between prey affect patch selection by predators

“…Since then, it has become clear that many more factors are involved in patch selection by predators, such as the need for a mixed diet (Belovsky 1978; Mayntz et al 2005; Marques et al 2015) and the avoidance of competing species (Janssen et al 1995; Adler et al 2001) and of intraguild predators (Moran and Hurd 1994; Magalhães et al 2005; Choh et al 2010). Also, when different prey species co-occur on the same patch, the interactions between these prey can affect patch quality and patch selection for predators (Werner and Peacor 2003; Ohgushi 2005; Schmitz et al 2008).…”

Integration of Plant Defense Traits with Biological Control of Arthropod Pests: Challenges and Opportunities

“…For example, Hilbeck et al (1998a) reported that the generalist predator C. carnea experienced reduced larval survival and longer development time when fed a diet of European corn borer (ECB), Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae), that had consumed Bt corn. However, generalist predators are capable of preferential feeding on healthy prey (Ferry et al, 2006) and are able to shift their dietary preferences to consume the mixture of nutrients required for optimal fitness (Mayntz et al, 2005; Raubenheimer et al, 2007; Marques et al, 2015). Therefore, generalist predators may be able to compensate for reduced quality of select prey due to Bt toxin consumption, having a negligible impact on biological control.…”

Reciprocal intraguild predation and predator coexistence

“…Although this disruption does not seem to occur very often, it does in some systems (Janssen et al., ; Rosenheim & Harmon, ). We therefore investigated the occurrence of IGP and reciprocal IGP between two predatory mite species that are considered for biological control of pests of the biodiesel plant Jatropha curcas L., on which both species occur (Marques et al., ; Sarmento et al., ).…”

“…We therefore investigated the occurrence of IGP and reciprocal IGP between two predatory mite species that are considered for biological control of pests of the biodiesel plant Jatropha curcas L., on which both species occur (Marques et al, 2015;Sarmento et al, 2011).…”