Host race evolution in the pyralid moth Dicymolomia Julianalis (Walker) on selected hosts in Tennessee

Dicymolomia julianalis (Walker) (Lepidoptera: Pyralidae) has a diverse feeding habitats, which range from herbivore to scavenger to predator. Allozyme analysis of fourteen loci was used to evaluate if populations of D. julianalis sampled from cat-tail, musk thistle, and common bagworm are genetically differentiated. Significant heterogeneity in allele frequencies exists at eight of nine loci examined. Analyses of population structure indicate that host is more important than geographic location in explaining the distribution of variation. Estimates of migration indicate that a restriction in gene flow exists among populations of D. julianalis. Genetic distances indicate that musk thistle and bagworm populations are more similar to each other than both are to cat-tail populations. The phenogram produced by UPGMA of Modified Rogers genetic distances indicate that two fairly separated groups exist in D. julianalis. The first group contains only cat-tail populations and the second musk thistle and common bagworm populations. The phenetic analysis indicates that the musk thistle race was most recently derived from the common bagworm race. Results of allozyme analysis indicate that populations of D. julianalis are genetically differentiated on these three hosts. As such, host race formation as the first step in sympatric speciation appears to be important in this species.