Integration of multiple cues allows threat-sensitive anti-intraguild predator responses in predatory mites

Abstract

Intraguild (IG) prey is commonly confronted with multiple IG predator species. However, the IG predation (IGP) risk for prey is not only dependent on the predator species, but also on inherent (intraspecific) characteristics of a given IG predator such as its life-stage, sex or gravidity and the associated prey needs. Thus, IG prey should have evolved the ability to integrate multiple IG predator cues, which should allow both inter- and intraspecific threat-sensitive anti-predator responses. Using a guild of plant-inhabiting predatory mites sharing spider mites as prey, we evaluated the effects of single and combined cues (eggs and/or chemical traces left by a predator female on the substrate) of the low risk IG predator Neoseiulus californicus and the high risk IG predator Amblyseius andersoni on time, distance and path shape parameters of the larval IG prey Phytoseiulus persimilis. IG prey discriminated between traces of the low and high risk IG predator, with and without additional presence of their eggs, indicating interspecific threat-sensitivity. The behavioural changes were manifest in distance moved, activity and path shape of IG prey. The cue combination of traces and eggs of the IG predators conveyed other information than each cue alone, allowing intraspecific threat-sensitive responses by IG prey apparent in changed velocities and distances moved. We argue that graded responses to single and combined IG predator cues are adaptive due to minimization of acceptance errors in IG prey decision making.

Keywords: direct predator cues; intraguild predation; phytoseiid mites; risk-sensitive behaviour.

Figure 1

The influence of cues (eggs, chemical traces left by a female on the substrate, traces and eggs) from the high risk IG predator A. andersoni (black bars), the low risk IG predator N. californicus (grey bars) and absence of IG predator cues (white bars) on time and distance parameters (mean + SE) of the IG prey larvae of P. persimilis in zones of leaf discs with high (leaf margin, A) and low (refuge, B) predator activity.

Figure 2

The influence of cues (eggs, chemical traces left by a female on the substrate, traces and eggs) from the high risk IG predator A. andersoni (black bars), the low risk IG predator N. californicus (grey bars) and absence of IG predator cues (white bars) on path shape parameters (mean + SE) of the IG prey larvae of P. persimilis in zones of leaf discs with high (leaf margin, A) and low (refuge, B) predator activity.