Clonal Reproduction and Polyploidy in Unisexual Hybrids of Phoxinus eos and Phoxinus neogaeus (Pisces; Cyprinidae)

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Abstract
Hybrids between Phoxinus eos and P. neogaeus are common, can occur in the absence of one parent species, and are almost exclusively female. Analyses of hybrids from eight localities in eastern North America indicate that these hybrids constitute a unisexual hybrid species, Tissue grafts among diploid hybrids from East Inlet, Coos Co., New Hampshire [USA] are accepted, indicating these unisexuals are genetically identical, and must be the products of clonal reproduction. Chromosome counts and isozyme banding patterns reveal the presence of both diploid and triploid hybrids at all eight localities. Gene dosage shown by electrophoretic analysis indicates that both eos .times. eox .times. neogaeus triploids and eos .times. neogaeus .times. neogaeus triploids exist. The three hybrid biotypes, one diploid and the other two triploid, are designated P. eos-neogaeus, P. 2 eos-neogaeus, and P. eos-2 neogaeus, respectively.