Geographic Variation in Variability of Pemphigus populicaulis

Publisher Website
Google Scholar
Abstract
Geographic variation of variability profiles is studied based on stem mother, alate and gall characters of the aphid P. populicaulis [from all regions of the USA]. Significant differences among the coefficients of variation of the suite of characters in every locality were found by 2 methods-Bartlett''s test for homogeneity of variances (using log-transformed data) and Friedman''s nonparametric test for randomized blocks. Nine characters are highly variable and 6 are consistently low in variability. Coefficients of variation show significant heterogeneity among localities for every character by Bartlett''s test, and for all but 2 characters using a modified Friedman''s test. The variability profiles of the 66 localities were clustered into 3 groups based on both size and shape by the k-means algorithm. A mixture of 2 types of profiles occurs throughout the middle latitudes of the study area, while the third type is found in its northern and southern regions. This geographic pattern may in part be due to the year of collection. Attempts to relate the magnitude of the coefficients of variation to several ecological indices were unsuccessful.

This publication has 3 references indexed in Scilit: