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Title: Population structure and genetic diversity within the endangered species Pityopsis ruthii (Asteraceae)

Author
item HATMAKER, ANNE - University Of Tennessee
item STATON, MARGARET - University Of Tennessee
item DATTILO, ADAM - Tennessee Valley Authority
item HADZIABDIC, DENITA - University Of Tennessee
item Rinehart, Timothy - Tim
item SCHILLING, EDWARD - University Of Tennessee
item TRIGIANO, ROBERT - University Of Tennessee
item Wadl, Phillip

Submitted to: Conservation Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2018
Publication Date: 7/11/2018
Citation: Hatmaker, A.E., Staton, M.E., Dattilo, A.J., Hadziabdic, D., Rinehart, T.A., Schilling, E.E., Trigiano, R.N., Wadl, P.A. 2018. Population structure and genetic diversity within the endangered species Pityopsis ruthii (Asteraceae). Conservation Genetics. 9:943. https://doi.org/10.3389/fpls.2018.00943.
DOI: https://doi.org/10.3389/fpls.2018.00943

Interpretive Summary: Ruth's golden aster (Pityopsis ruthii) is a federally endangered plant species that grows on rock boulders and distribution of the plant is limited to small sections of Hiwassee and Ocoee Rivers in in Tennessee. The species was designated as endangered in 1985 by the US Fish and Wildlife Service and since designation researchers have have attempted to understand factors limiting successful reproduction and geographic expansion, as well as to delineate the relationship of Ruth's golden aster. Understanding the population genetics, sexual reproduction, and methods for reintroduction of may reveal the optimum approach and tools needed to sustain this vulnerable species. Genetic studies of Ruth's golden aster are lacking and provide information to conservationists and researchers in order to facilitate preservation of the species. Therefore, researchers utilized molecular markers to determine population structure and conservation units for Ruth's golden aster, which is critical to long-term conservation and management efforts. Based on our results we recommend Ruth's golden aster be managed as four populations within the Hiwassee River and three populations within the Ocoee River. Understanding diversity within populations of Ruth's golden aster will impact the current conservation methods and management plans, as well as provide further information for population augmentation of the species such as replanting.

Technical Abstract: Pityopsis ruthii (Ruth’s golden aster) is a federally endangered herbaceous perennial endemic to the Hiwassee and Ocoee Rivers in southeastern Tennessee, United States. Comprehensive genetic studies providing novel information to conservationists for preservation of the species are lacking. Genetic variation and gene flow were evaluated for 814 individuals from 33 discrete locations using polymorphic microsatellites: seven chloroplast and twelve nuclear. A total of 198 alleles were detected with the nuclear loci and 79 alleles with the chloroplast loci. Gene flow was estimated, with the Hiwassee River (Nm = 2.16; FST = 0.15) showing higher levels of gene flow and lower levels of population differentiation than the Ocoee River (Nm = 1.28; FST = 0.19). Population structure was examined using Bayesian cluster analyses. Nuclear and chloroplast analyses were incongruent. From the chloroplast microsatellites, three clusters were identified; all were present in sampling sites at both rivers, indicating a lack of allele fixation along rivers. Nuclear markers revealed two clusters and separated by river. When the Hiwassee River locations were analyzed, four clusters were identified for both the chloroplast and nuclear microsatellites, though the individuals clustered differently. Analysis of the Ocoee River revealed two clusters for the chloroplast microsatellites and three for the nuclear microsatellites. We recommend P. ruthii be managed as four populations for the Hiwassee River and three populations for the Ocoee River. Our results provide critical genetic information for P. ruthii that can be used for species management decisions to drive future population augmentation/reintroduction and ex situ conservation efforts.