Natural enemies partially compensate for warming induced excess herbivory in an organic growth system

Orsolya Beleznai,Ferenc Samu,Zoltán Tóth,Jamin Dreyer

doi:10.1038/s41598-017-07509-w

Orsolya Beleznai, Ferenc Samu + Show 2 more

Open Access

https://doi.org/10.1038/s41598-017-07509-w

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Abstract

Predators can limit prey abundance and/or levels of activity. The magnitudes of these effects are contingent on predator and prey traits that may change with environmental conditions. Aberrant thermal regimes could disrupt pest suppression through asymmetric effects, e.g. heat-sensitive predator vs. heat-tolerant prey. To explore potential effects of warming on suppressing pests and controlling herbivory in a vegetable crop, we performed laboratory experiments exposing an important pest species to two spider predator species at different temperatures. Heat tolerance was characterised by the critical thermal maxima parameter (CTM50) of the cucumber beetle (Diabrotica undecimpunctata), wolf spider (Tigrosa helluo), and nursery web spider (Pisaurina mira). Cucumber beetles and wolf spiders were equally heat tolerant (CTM50 > 40 °C), but nursery web spiders had limited heat tolerance (CTM50 = 34 °C). Inside mesocosms, beetle feeding increased with temperature, wolf spiders were always effective predators, nursery web spiders were less lethal at high temperature (38 °C). Neither spider species reduced herbivory at ambient temperature (22 °C), however, at warm temperature both species reduced herbivory with evidence of a dominant non-consumptive effect. Our experiments highlight the contingent nature of predator-prey interactions and suggest that non-consumptive effects should not be ignored when assessing the impact of temperature change.

Highlights

Predators can negatively impact prey populations either by directly consuming prey individuals or through non-consumptive effects (NCEs) that trigger costly anti-predator reaction in prey[1]
Expected elevated temperatures arising from global climate change, and high temperatures caused by some agricultural practices, such as greenhouse growing[14], plastic mulch and foil covers[15, 16] make it necessary to study how different interactions may change under altered thermal conditions
The calculated critical thermal maximum parameters indicated that cucumber beetles and the lycosid spider had high heat tolerance, with largely overlapping confidence intervals, while the pisaurid spider proved to be much less heat tolerant (CTM50 = 34.2 °C, 95% CI [33.19, 35.15]) (Fig. 1)

Summary

Introduction

Predators can negatively impact prey populations either by directly consuming prey individuals or through non-consumptive effects (NCEs) that trigger costly anti-predator reaction in prey[1]. Predator effects have the potential to cascade through ecological systems, affecting productivity and ecosystem functioning at the lower levels of the food web[6] and shaping ecological interactions spatially[7] Elements at both sides of this interaction, predator activity, performance and the success or failure of the prey’s anti-predator behaviour are contingent on environmental factors. These effects gain economic importance in the natural enemy – pest context, especially in the view of global climate change. In a recent experimental study of the natural enemy complex of grapevine pests synergistic effects between predators have been shown to increase under increased temperatures[34]

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