Isozyme Variation Among Mountain Pine Beetle ( Dendroctonus ponderosae ) Populations in the Pacific Northwest

Abstract

To examine genetic variation among mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Scolytidae), populations in the Pacific Northwest, beetles from 6 localities were assayed for isozyme variation using starch gel electrophoresis. Greater genetic differences were observed among males in many samples than among the females. A cline in gene frequencies at the aspartate aminotransferase locus corresponded to north-south geographic distribution of beetle populations in Idaho. Similarity coefficients calculated between all possible pairs of populations indicated the presence of 2 major population units. The largest differences between populations appear to be attributable to long-term geographic isolation.