Morphometric variation within and between populations of the pine aphid, Cinara nigra (Wilson) (Homoptera: Aphidoidea: Lachnidae), in western North America

Abstract

Morphological variation in Cinara nigra (Wilson), found on Pinus contorta Dougl. ex Loud, throughout western North America, was characterized with the aid of univariate and multivariate statistical methods. Within-population variation in one sample collected near Edson, Alberta, was examined. Correlation and principal component analysis revealed patterns of interdependence among characters as well as patterns of size and size-related shape variation in 52 characters. To examine morphological variation between 19 geographic samples, this initial set was reduced in two steps to 49 and 32 characters, respectively; the reduction did not result in a significant loss of information content. No geographic pattern in clusters of samples was revealed either by the ordination of sample centroids or by UPGMA cluster analysis of the Mahalanobis D values. The taxonomic implications of this morphometric analysis are discussed, in particular the usefulness of various morphological attributes for species discrimination.