Deciphering Biological Groupings in the Essigella knowltoni Complex (Homoptera: Aphidinea: Lachnidae), and Comparison to Variation in Pinus contorta (Coniferae: Pinaceae)
Sorensen, John T.
Aphids of the species complex of Essigella knowltoni Hottes 1957 were sampled throughout their range in the W'Nearctic on their host, Pinus contorta. Aphid variance was assessed for 53 morphometric traits using principle component analysis, and for qualitative traits by geographical plots. Because quantitative and qualitative data were non-congruent among the populations, both data types were analyzed in a composite matrix for a consensus of relationships. The matrix, consisting of coded qualitative traits plus the 6 dominant vectors of the principal component analysis, was clustered and revealed 3 groups of aphids. The groups show reasonable concordance with geography when superimposed, but also display nonclinal disjunctures between the geographically proximal samples of opposing groups. Group diagnostics were established. Discriminant function analysis was used to verify intergroup distances. Aphid variance showed a close compatibility to morphological, isozyme and monoterpene variance among their hosts, suggesting historical evolutionary resource-tracking of the host plant by the insect.