Allozyme analysis of clonal diversity among unisexual hybrids of the killifishes Fundulus diaphanus and F-heteroclitus

Hybrids of the killifish species Fundulus diaphanus and F. heteroclitus are diploid unisexual gynogens producing genetically identical, all-female off spring without a genetic contribution from males. We used isozymes to asses s clonal diversity at the two localities in Nova Scotia where the unisexual hybrids are known to occur. Four isozyme loci, fixed for different alleles in the two parental species and heterozygous in the hybrids, served to dis tinguish the three taxa, In addition to these four loci, ADA* was polymorph ic in F, diaphanus but monomorphic in nearly all of the hybrids, which sugg ests that clonal diversity cannot be high among the hybrids. And sIDHP*, fi xed for different alleles in F, diaphanus and F, heteroclitus, appeared hom ozygous in nearly all hybrids for the allele characteristic of F. heterocli tus, This homozygosity may be the result of gene regulation, a null allele, a rare recombinational event, or undetected variability in F, diaphanus, S ome of these explanations suggest a rare event in the history of these homo zygous unisexuals, indicating that they comprise a single clone, although o ther explanations for this homozygosity do not rule out the presence of mul tiple clones.