Date of Award


Document Type


Degree Name

Master of Science




As many as five different populations of Etheostoma nigrum and Etheostoma olmstedi have been identified in the James River drainage, Virginia. Genetic variation of these populations was analyzed with starch gel electrophoresis and revealed only three distinct populations. Nine loci encoding five enzyme systems and two loci encoding muscle proteins were examined in tissue homogenates. All populations were monomorphic with the exception of the esterase-3 (Est-3), phosphoglucomutase (Pgm-1) and phosphoglucose isomerase (Pgi) loci. Two alleles of Est-3 exhibited activity in the homozygous and heterozygous conditions. Pgm-1 occurred as two alleles with a high degree of heterozygosity (46% for E. nigrum and 54% for E. olmstedi). The Pgi-1 allele in both the homozygous and heterozygous condition was species specific for Etheostoma nigrum whereas the presence of Pgi-1 and Pgi-2 in the homozygous state was diagnostic of E. olmstedi. Etheostoma nigruminhabited the Piedmont section of the James above the Fall Line; E. olmstedi occupied the Coastal Plain segment of the river and the Appomattox River drainage. The two species occurred sympatrically in Falling Creek. No electrophoretic evidence was found for hybridization between the two forms. Banding patterns for all loci examined were the same for the subspecies E. o. olmstedi and E. o. atromaculatum. Overall heterozygosity was higher for E. nigrum (10.3%) than E. olmstedi. (5.1%) but both were within the range reported for teleosts.

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