Abstract
Two visual abundance methods were used to estimate the density of healthy or mummified aphids, Aphis gossypii Glover, on leaves and whole cucumber plants in greenhouses. Additional explanatory variables (e.g., proportion of infested leaves per plant or number of leaves per plant) were collected at the same time. Precise counts were also made on the same spatial units and fit to visual class data along with the explanatory variables using multiple regression with Poisson errors, logistic regression, and projection pursuit regression. Smaller subsets of data were used to test the robustness of the regression models. Multiple regression with Poisson errors gave the least precise fits in all cases, and the projection pursuit regression gave slightly better predictions than logistic regression. The accuracy of the logistic regression was similar for both the reference and the validation data sets. Visual abundance estimates and the associated explanatory variables are easy to gather, and when substituted into the projection pursuit regression model, they can be used to estimate aphid densities. Such models are useful in metapopulation studies of highly abundant organisms where extensive census data are required.
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Claims 4
Claim · model-written summary
Poisson multiple regression gave the least precise fits for aphid density estimation in all cases.
Verbatim
e0“Multiple regression with Poisson errors gave the least precise fits in all cases”
Claim · model-written summary
Projection pursuit regression predicted aphid density slightly better than logistic regression.
Verbatim
e0“the projection pursuit regression gave slightly better predictions than logistic regression”
Claim · model-written summary
Logistic regression accuracy was similar for reference and validation data.
Verbatim
e0“The accuracy of the logistic regression was similar for both the reference and the validation data sets”
Claim · model-written summary
Visual abundance estimates and explanatory variables in the projection pursuit model can estimate aphid densities.
Not reportedComparator
Verbatim
e0“Visual abundance estimates and the associated explanatory variables are easy to gather, and when substituted into the projection pursuit regression model, they can be used to estimate aphid densities”