Abstract

Choosing intraguild (IG) predator free prey patches for egg deposition is an important mechanism to limit the intraguild predation (IGP) risk for offspring. Heat stress, however, may alter the strength of oviposition site selection. The exotic predatory mite Amblyseius swirskii (Athias-Henriot) is an aggressive IG predator, which is often used as biocontrol agent together with the native predatory mite Typhlodromus bagdasarjani Wainstein & Arutunjan in different greenhouse crops in Iran. Thus, we examined egg distribution and oviposition behavior of exotic and native predator females when having choice between spider mite (Tetranychus urticae Koch eggs and larvae) prey patches with and without IG predator cues (traces and eggs of IG predator females) at three alternating temperature regimes [(40°C/15°C), (35°C/13°C) and (30°C/13°C), 16:8 (L: D) h photoperiod and 65±5% RH]. The number of laid eggs and consumption rates were checked daily over 3 consecutive days. The oviposition rates of native females were not affected by temperature, but they deposited more eggs in IG predator free prey patches. The predation rates of native females on spider mites decreased under heat stress. The exotic predator females, however, laid more eggs in prey patches with IG predator cues and in contrast to native females also killed IG predator eggs. Heat stress reduced the oviposition rates of the exotic predator, whereas the consumption rates on spider mites and IG predator eggs were unaffected by temperature. Our results indicate that exotic A. swirskii and native T. bagdasarjani females display divergent oviposition strategies under heat stress. Independent of temperature, native females reduced IGP risk by avoiding egg deposition in the presence of IG predator cues. Additionally, the reduced consumption rates on spider mites under heat stress may have resulted in smaller egg sizes of native females, because oviposition rates were not affected by temperature. Contrary, heat stress lowered the reproductive output of the exotic predator females, but not their consumption rates on spider mites. Additionally, IG predator cues seemed to be attractive for the exotic predator females, because they clearly preferred prey patches containing IG predator traces and eggs for oviposition. IGP risk for exotic offspring was reduced by killing IG predator eggs. If these different IG anti-predator strategies lead to coexistence of exotic A. swirskii and native T. bagdasarjani in Iranian greenhouse crops under heat stress, remains an open question.