Title

Over the Falls: The Effects of Barriers on Gene Flow and Genetic Structure in Rhinichthys atratalus, the Eastern Blacknose Dace

Publication Date

April 2018

Advisor(s)

Barry Chernoff

Major

Biology (BIOL)

Language

English (United States)

Abstract

Waterfalls have been found to act as barriers to gene flow in riverine communities, affecting migration and genetic diversity of fish populations. We studied nuclear microsatellites and the mitochondrial gene nd2 of Rhinichthys atratalus, the Eastern Blacknose Dace, to test hypotheses about genetic diversity. Specifically, we investigated whether the largest genetic differences between populations are due to the presence of waterfalls. Based on literature, we also hypothesized that the greatest genetic diversity would be found in populations below waterfalls. 145 individuals from five localities above and below waterfalls were collected and analyzed. Nd2 results indicated that below-falls populations had higher haplotype and nucleotide diversity, while above-falls populations had a greater number of private haplotypes. For microsatellites, above-falls populations also had a greater number of private alleles, and the majority of the significant variation between populations resulted from heterozygosity within individuals. Migration rates between populations were estimated to be fairly high, even between physically non-connected sites, which we attribute to the influence of shared haplotypes and alleles between populations. A reduced major axis (RMA) regression and Mantel test were nonsignificant, indicating that genetic differences cannot be explained by an isolation by distance model of evolution. We found that populations were genetically distinct whether or not they were separated by visible barriers, and the presence of waterfalls was not associated with a higher magnitude of genetic difference between populations.

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