Density-dependent dispersal may explain the mid-season crash in some aphid populations |
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Authors: | Alla Mashanova Alan C Gange Vincent A A Jansen |
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Institution: | (1) School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, TW20 0EX, UK |
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Abstract: | Aphid population dynamics during the season show a characteristic pattern with rapid increase in numbers at the beginning
followed by a sudden drop in the middle of the season. This pattern is usually associated with predation and/or change in
food quality during the summer. By developing a mechanistic model of aphid population dynamics we show that this pattern can
arise from density-dependent dispersal behaviour of aphids. The dynamics produced by the model were similar to those observed
in real populations of the alder aphid (Pterocallis alni). The two mechanisms required for these oscillations to arise were the perception of density through the number of contacts
with other individuals and the inter-generational transfer of information (the maternal effect). Both mechanisms are examples
of delayed density-dependence and, therefore, this study adds to the evidence that delayed density-dependence might cause
complex population dynamics. To reproduce the seasonal dynamics of the alder aphid with the model, the maternal effect was
essential, indicating that this could be an important factor in alder aphid dynamics. According to our model, external regulations
(e.g., predation and/or change in food quality) were not required to explain the highly oscillatory population dynamics of
aphids during a season. |
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Keywords: | Emigration Maternal effect Mechanistic model Oscillations Population dynamics |
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