Hatcheries maintain high genetic variation but show shifts in genetic structure of progenies of five endangered riffleshell species (Epioblasma) (Bivalvia: Unionidae) of the eastern United States

Abstract

We assessed genetic variation at mitochondrial DNA (mtDNA) and nuclear DNA microsatellites for progeny (i.e., juveniles produced at a hatchery) of five endangered Epioblasma species reared at three hatcheries in the eastern United States. The progeny of Epioblasma aureola, Epioblasma brevidens, Epioblasma obliquata and Epioblasma triquetra showed no loss of mtDNA haplotype diversity relative to broodstock (i.e., wild collected gravid females used to produce juveniles) and wildstock (i.e., individuals sampled in the wild to assess baseline genetic diversity), while progeny of Epioblasma capsaeformis showed no loss relative to broodstock but an ~50% loss relative to wildstock. At DNA microsatellites, mean expected heterozygosities (He) were maintained in wildstock, broodstock and progeny, with the lowest values observed in E. aureola and E. triquetra. Among progeny, values of He and allelic richness (A) at times exceeded those observed in the wildstock and broodstock. Hence, no loss of genetic variation at DNA microsatellites was observed in progeny among species. We documented multiple paternity in progeny of E. aureola, E. capsaeformis and E. obliquata and in part attribute their high He and A to fertilization of broodstock females by multiple males in the wild. We observed significant divergence in FST and D values between progeny to wildstock and progeny to broodstock. Most pairwise comparisons for E. brevidens and E. capsaeformis were significantly diverged, and for E. obliquata, divergence was low but also significantly different, and only for E. aureola was it low and nonsignificant. Our results showed that population genetic structure can develop quickly between progeny and their progenitors in the first generation (F1) of offspring produced from a set of parents and that genetic diversity at mtDNA and nuclear DNA microsatellites was generally maintained in progeny of endangered Epioblasma species reared at three mussel hatcheries utilizing current propagation practices.