We can precisely predict the future dynamics of populations only if we know the underlying mechanism of population dynamics. Long‐term data are important for the elucidation of such mechanisms. In this article we analyze the 50‐year dynamics of annual light‐trap catches of three insect pest species living in paddy fields in Japan: the rice stem borer, Chilo suppressalis (Walker) (Lepidoptera: Pyralidae); the green rice leafhopper, Nephotettix cincticeps (Uhler) (Hemiptera: Deltocephalidae); and the small brown planthopper, Laodelphax striatellus (Fallén) (Hemiptera: Delphacidae). We separate the long‐term dynamics into two components by using locally weighted scatterplot smoothing: (1) the underlying dynamics of populations, and (2) the influence of the past changes in the environment. The former component is analyzed by response surface analysis and vector autoregression to evaluate the nonlinearity of density‐dependence and the inter‐specific influence of density, respectively. On the basis of these analyses, we perform the state‐space model analyses. The state‐space model selected by Akaike's information criterion indicates that the observed number of light‐trap catches of C. suppressalis and N. cincticeps in summer increases with increasing temperatures in the previous winter. It also indicates that the influence of temperature is not carried over to the next year. We utilize the selected model to predict the impact of global warming on these species, by substituting the temperature predicted by a general circulation model.
Population subdivision and connectivity within a distribution range are important factors to consider in the development of a management strategy to control widespread pest species. Damage by sorghum plant bug, Stenotus rubrovittatus (Matsumura), has rapidly spread across Japan over the last 10 years. To characterize the fine-scale population structure of this bug and investigate the boundaries of genetic isolation, we analyzed the population structure of 21 local populations within a 72 km 9 200 km area around Fukushima and Ibaraki prefectures. Polymorphism of six microsatellite markers implied that S. rubrovittatus in the study area was divided into northern and southern genetic groups segregated by the 37.3°N line of latitude. The boundary between the two groups, defined by microsatellites, was almost consistent with the range limit of one mitochondrial lineage of the same species. Our result indicated that isolation between these two genetic groups was mediated by historical and ecological origins, and was maintained during the last 10 years when there were rapid outbreaks of this species on rice within the study area.
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