Hybridization and Biochemical Genetics of Black and White Crappies in the Southeastern USA

Abstract

Populations of black crappie Pomoxis nigromaculatus and white crappie P. annularis in Alabama, Arkansas, and Tennessee were examined for isozyme variation. Twelve diagnostic loci distinguished these two species. Both species exhibited low levels of genetic variation. Percentages of loci polymorphic in populations of black and white crappies were 0–4.7% and 0–11.6%, respectively. Mean heterozygosities were 0.000–0.008 and 0.000–0.012 for black and white crappie populations, respectively. Although extremely low levels of genetic variation were detected within or among white or black crappie populations when only nonhybrid individuals were considered, there were some distinct differences among populations within each species. Populations in Tennessee tended to have a greater number of unique, low-frequency, variant alleles than other crappie populations. Black crappies possessing the blacknose trait had allele frequencies similar to those of black crappies with normal coloration. Natural hybridization was common between the two species and was the major source of genetic variation. The extent of hybridization varied among reservoirs and hatcheries. In three of eight sites sampled, 29.3 to 54.5% of the individuals were F1 or Fn hybrids (n = 2, 3, …); F1 hybrids were more likely to be found in reservoirs than in hatcheries, and Fn hybrids were found in both reservoirs and hatcheries.