Abstract
Genetic variation at 22 nuclear-encoded loci (21 microsatellites and one anonymous locus) and at mitochondrial (mt)DNA was examined among 40 Cape Fear Shiners (Notropis mekistocholas) sampled from the third generation of offspring raised in captivity and among 44 individuals sampled from the “wild” population from which the captive stock was originally constituted. Levels of genetic diversity in both samples were high as compared to other freshwater fishes. However, lower genetic diversity, as reflected by lower number of alleles and gene diversity (nuclear-encoded loci) and number of haplotypes and nucleon diversity (mtDNA), was found in the captive population. Kinship analyses revealed 101 significant half-sib and full-sib relationships in the sample from the captive population versus 83 in the sample from the wild population. Polygynous matings were suggested by the occurrence of 51 significant half-sib relationships that did not share mtDNA haplotypes; polyandrous matings also may have occurred but could not be inferred reliably from the analysis. Effective population size, estimated using a linkage disequilibrium approach, was 49 (95% CI: 43–56) for the captive population and was ∼10 times smaller than that estimated for the wild population 528 (273–5336). Considering the low number of founders (31) originally used to constitute the captive stock, the estimate for the captive population indicates that a high proportion of the adults present at each generation actually contributed to the offspring. This suggests that relatively large effective population sizes may be achieved in captive populations of N. mekistocholas provided a large number of breeding adults are used.