Dispersion analyses and resource utilization of aphid parasitoids in a non-depletable environment |
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Authors: | John T Trumble and Earl R Oatman |
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Institution: | (1) Department of Entomology, University of California, 92521 Riverside, CA, USA |
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Abstract: | Summary Dispersions and resource utilization of primary and secondary parasitoids developing in non-depletable primary host populations
were determined for an aphid-parasitoid community occurring on strawberries. Analyses of dispersions based onGreen's coefficient andLloyd's Patchiness Index indicated parasitized aphids were highly aggregated initially, became less aggregated as density increased,
and remained aggregated following collapse of the aphid populations. The “index of aggregation” values calculated usingTaylor's Power Law concurred with results from the other indices, and the similarity of the regression coefficients from both seasons
suggests that the index of aggregation may be characteristic for communities as well as species. Analysis withIwao's regression of mean crowding on the mean generated similar results when population data were stratified temporally, and
also indicated that the individual was the basic unit of the population.
In a non-depletable environment, oviposition of individuals exhibiting an aggregated dispersion pattern within clumps of hosts
provides primary parasitoids with a suitable trade-off between energy utilization or genetic potential, and losses associated
with hyperparasitism. |
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