Comparison of domestic and wild channel catfish (Ictalurus punctatus) populations provides no evidence for genetic impact

Genetic diversity of wild channel catfish (Ictalurus punctatus) populations was analyzed using AFLP markers and compared to that of domestic catfish populations to determine the genetic impact of domestic catfish on wild catfish populations. Fourteen wild populations within various watersheds of Alabama were analyzed using five AFLP primer combinations. A total of 396 polymorphic bands were detected from 269 individuals, with an expected mean heterozygosity of 0.16. The percentage of polymorphic bands varied greatly among populations, from 32.2% to 85.0%. The estimated level of population differentiation as measured by average FST value across all loci was 0.36. The 14 tested wild populations were related with 88% similarity as revealed by Nei's (Nei, M., 1978. Estimation of average heterozygosity and genetic distance from a small number of individuals. Genetics 89, 583-590) unbiased population-wise identity measures. In order to analyze the interactions between domestic and wild populations of channel catfish, 191 polymorphic bands were used to evaluate 569 individuals from 31 populations. The wild populations exhibited higher levels of polymorphisms and heterozygosities than the domestic populations. Strong genetic structures were associated with the geographical distribution of samples, with all samples from a single watershed being closely related. The domestic populations were all related to one another, forming a single branch in the phylogenetic analysis, while all but the Tennessee River populations of many wild populations were more related to one another than to domestic populations. Genetic identities of wild fish from proximal and distal sites were similar, while both wild populations differed from the nearby domestic catfish populations, providing no molecular genetic evidence for apparent impact of domestic catfish on wild populations.