Density dependence depends on scale; at larval resource patch and at whole population |
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Authors: | Midori Tuda |
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Institution: | (1) Department of Biology, College of Arts and Sciences, University of Tokyo, Komaba, Meguro-ku, 153 Tokyo, Japan |
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Abstract: | Summary A previous study (Tuda and Shimada, 1993) has shown that the equilibrium population size of the azuki bean beetle was lower
at 32°C than at 30°C and that this difference was due to a reduced maximum population size of emerged progeny through inside-bean
process. In this paper, these results were analyzed further on the scale of the individual bean where interaction among larvae
took place. Per-bean numbers of deposited eggs, hatched eggs, and emerged adults have been recorded at seven different parental
densities under the two temperature conditions.
Three individual-bean-scale process hypotheses that may explain the reduced maximum emergence density on the whole population
scale are suggested: (1) a lower maximum emergence per bean at 32°C than at 30°C, if the bean scale and the wholepopulation
scale share the same density-dependent pattern in adult emergence, (2) a limited range of hatched egg number per bean at 32°C,
resulting from the adult oviposition process outside beans, and (3) different patterns of density-dependent emergence between
the two different scales.
This study showed that the inside-bean pattern of responses on the bean scale was a simple saturated curve at 30°C, but one
with a discontinuous decline at higher hatched egg densities at 32°C. On the contrary, during outside-bean process, the peak
number of hatched eggs decreased on this scale as observed on the wholepopulation scale. I discuss why the extracted factor
of inside-bean process on the whole-population in the previous study could not be applied to the bean-scale pattern. |
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Keywords: | spatial scale resource patch intraspecific competition temperature Callosobruchus chinensis density-dependent response |
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