Genetic Variation within and among Geographic Populations of Diabrotica barberi (Coleoptera: Chrysomelidae)1

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Abstract
Adult enzymatic and chromatic variation data were compiled and compared for geographic populations of Diabrotica barberi Smith and Lawrence. Genetic distance values, computed between populations based on electromorph frequencies, ranged from 0.001 to 0.063 (avg = 0.013). There was an approximate relation between the magnitude of given values and the geographic distance separating sampling units. Multidimensional scaling of the genetic distance matrix produced a spatial plot of populations that approximated their actual geographic distribution. Correlation coefficients calculated between populations ranged from 0.865 to 0.988 and provided additional evidence of a close correspondence between paired isozyme data sets. Recorded population heterozygosities ranged from 0.053 to 0.123 and heterozygosity averaged 0.081 over all populations. Observed levels of heterozygosity did not vary significantly among populations nor were there significant differences between observed and expected heterozygosities. Variation partitioning based on heterozygosity estimates indicated that 90.2% of the total species variation could be found in given populations. Significant correlations were recorded between electromorph heterozygosities and color variation scores of adult morphological structures. The data support the idea that chromatically varying beetle populations represent geographic races of D. barberi, despite the existence of complex color patterns over given regions of the species distribution.