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

Abstract

Hybrids of the killifish species Fundulus diaphanus and F. heteroclitus are diploid unisexual gynogens producing genetically identical, all-female offspring without a genetic contribution from males. We used isozymes to assess 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 distinguish the three taxa. In addition to these four loci, ADA* was polymorphic in F. diaphanus but monomorphic in nearly all of the hybrids, which suggests that clonal diversity cannot be high among the hybrids. And sIDHP*, fixed for different alleles in F. diaphanus and F. heteroclitus, appeared homozygous in nearly all hybrids for the allele characteristic of F. heteroclitus. This homozygosity may be the result of gene regulation, a null allele, a rare recombinational event, or undetected variability in F. diaphanus. Some of these explanations suggest a rare event in the history of these homozygous unisexuals, indicating that they comprise a single clone, although other explanations for this homozygosity do not rule out the presence of multiple clones.