GENETIC DIFFERENTIATION AMONG HOST-ASSOCIATED POPULATIONS OF THE GALLMAKER EUROSTA SOLIDAGINIS (DIPTERA: TEPHRITIDAE)

Eurosta solidaginis, a gallmaking tephritid (Diptera), infests at least two species of Solidago in the eastern United States. We used horizontal starch gel electrophoresis of enzymes to examine whether populations on the two principal host plant species, Solidago altissima and S. gigantea, have diverged genetically. At the d-β-hydroxybutyrate dehydrogenase (HBDH) locus, the predominant allele in all nine populations from S. altissima (HBDH^1.00 ) was absent or uncommon in all but 1 of the 12 populations from S. gigantea. At the phosphoglucomutase locus (PGM), the most common allele in all populations was PGM^1.00 , but the frequency of this allele was, with one exception, higher in populations from S. gigantea than in populations from S. altissima. Genetic heterozygosity was usually greater in populations from S. altissima (H̄ = 0.028) than in populations from S. gigantea (H̄ = 0.009). A phylogenetic tree derived from a genetic distance matrix clustered gallmaker populations from the same host plant together.