Recurrent Insect Outbreaks Caused by Temperature-Driven Changes in System Stability

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Science  16 Aug 2013:
Vol. 341, Issue 6147, pp. 796-799
DOI: 10.1126/science.1238477

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Insect Cycles

Rapid increases in insect populatio n sizes can result in significant crop losses. Seasonal temperature has been proposed to drive such outbreaks. Despite clear evidence that temperature can drive individual insect development, its influence at the population level is much less clear. Nelson et al. (p. 796, published online 1 August) analyzed data collected over 50 years on the tea tortrix moth, which affects Japanese tea plantations, to reveal the impacts of temperature on cyclical outbreaks.


Insects often undergo regular outbreaks in population density but identifying the causal mechanism for such outbreaks in any particular species has proven difficult. Here, we show that outbreak cycles in the tea tortrix Adoxophyes honmai can be explained by temperature-driven changes in system stability. Wavelet analysis of a 51-year time series spanning more than 200 outbreaks reveals a threshold in outbreak amplitude each spring when temperature exceeds 15°C and a secession of outbreaks each fall as temperature decreases. This is in close agreement with our independently parameterized mathematical model that predicts the system crosses a Hopf bifurcation from stability to sustained cycles as temperature increases. These results suggest that temperature can alter system stability and provide an explanation for generation cycles in multivoltine insects.

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