Experimental warming effects on the population growth and composition of a crop pest (soybean aphid) and the consequences for pest colonization under biocontrol
Date Issued
2015
Date
2015
Author(s)
Wang, Ying-Jie
Abstract
Understanding warming impact on agricultural system is important because it is related to food security. While it has been known that the response of crop pests to warming (e.g. higher population under warming) is a critical mechanism for the change in crop production under warming (e.g. reduced crop yield), some knowledge gaps remain. For example, it is unclear if warming will affect not only the population size but also the population composition of pests (e.g. alate vs. apterous), consequently changing pest colonization. In addition, warming impact on a tri-trophic system (crop, pest, predator) is less explored. To help fill up the knowledge gaps, this study examined soybeans, soybean aphids, and ladybugs because they represent an important crop, pest, and biocontrol agent, respectively. I first investigated how an experimental warming of 2-4 oC (predicted future warming) would affect aphid population growth and alate proportion in a laboratory. The results showed that warming suppressed alate production (from about 5 to 1 %) without affecting the total aphid population (alate and apterous). Based on the warming experiment results, I then manipulated the initial alate proportion accordingly (warming vs. ambient) in a field colonizatoin experiment, and observed how fast aphids would colonize soybeans in open-top chambers under the presence and absence of a ladybird beetle (major predator and biocontrol agent of aphids). I found interactive effects of alate proportion and predation. Specifically, when the initial proportion of alate aphids was high (5 %; ambient-temperature scenario), aphid outbreaks happened earlier in the presence of a predator. In contrast, when the initial proportion of alate aphids was low (1%; warming scenario), aphid outbreaks happened later in the presence of a predator. Modelings could replicate similar results, suggesting that warming impact on pest population composition (alate proportion) can interact with predator treatment (biocontrol). These results suggest that warming around optimal temperature of soybean aphids may not increase their initial population size but limit their colonization potential by changing population composition (alate proportion), consequently making aphids more susceptible to predation. In other words, biocontrol using predators could become more promising in limiting pest outbreaks and protecting crop yield under future climate change.
Subjects
warming
population composition
tri-trophic food chain
interspecific interaction
pest biocontrol
Type
thesis
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