Biases in the estimation of spatial egg aggregation and association based on emergence data |
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Authors: | Kazuo H Takahashi |
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Institution: | (1) Ecology and Genetics, Graduate School of Environmental Earth Science, Hokkaido University, Kita 10 Nishi 5, Sapporo 060-0810, Japan;(2) Present address: Division of Population Genetics, National Institute of Genetics, Mishima, Japan |
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Abstract: | Spatial aggregation and association of conspecific and allospecific eggs over resource patches have often been estimated based
on emergence data. However, intra-specific competition reduces the number of emergents of conspecifics, and inter-specific
competition reduces the number of emergents of allospecifics, causing biases in the estimation of spatial distribution of
eggs using emergence data. The present study investigated, by laboratory experiments using drosophilids and simulation models,
how the use of emergence data causes such biases. In the laboratory experiments, females were allowed to oviposit over resource
patches, and spatial aggregation and association of eggs were examined. The number of emergents from each resource patch was
then estimated from the density-survival relationship, and spatial aggregation and association of emerging adults thus estimated
were compared with those of eggs. In the simulation models, the spatial distributions of adults emerging from eggs that varied
in their degree of spatial aggregation were evaluated under different intensities of intra- and/or inter-specific competition.
Both laboratory experiments and simulations indicate that the use of emergence data always causes an underestimation of spatial
aggregation and association of eggs. Relaxation of intra- and inter-specific competition by addition of extra resources would
improve the estimation of spatial egg distribution based on emergence data. |
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Keywords: | Aggregation model Drosophila Inter-specific competition Intra-specific competition Patchy resource |
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