Population Structure and Genetic Diversity Within the Endangered Species Pityopsis ruthii (Asteraceae)

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.

Complete chloroplast genome comparisons for Pityopsis (Asteraceae)

“…tracyi. This study used tissue collected in 2010 and 2013 and kept at -80˚C from P. ruthii [14], P. falcata, and P. graminifolia…”

“…The draft genomes were then gapfilled within Geneious [28] using the "map to reference" option. We also assembled a cp genome from a second P. ruthii individual for quality control using sequencing data from previous work [14] (S1-S3 Tables) and the same methodology.…”

“…Nuclear microsatellites have been developed for two different Pityopsis species and chloroplast microsatellites have been developed for one species [14][15][16]. However, whole chloroplast (cp) genomes are lacking for all species in the genus.…”

Genetic diversity of alpine Dryas octopetala populations at their southern distribution limit in Europe

“…Although RAPDs are dominant markers, we calculated (although biased) the p and q allelic frequencies according to the Hardy–Weinberg law by considering genotypes AA (p 2 ) and Aa (2pq) as one (Allele frequency = p, band present) and genotype aa (q 2 ) as one (Allele frequency = q, band absent) (Lynch and Milligan 1994, de Vicente et al 2004, Nag et al 2013). From the allelic frequencies we calculated the intralocus genetic diversity (h) and Shannon's information index (I) (de Vicente et al 2004, Hatmaker et al 2018).…”

Genetic diversity and structure of Saussurea polylepis (Asteraceae) on continental islands of Korea: Implications for conservation strategies and management

“…Population genetic studies often elucidate demographic histories and evolutionary processes in humans [ 1 , 2 ], animals [ 3 , 4 ], and plants [ 5 – 7 ]. A few of the many plant studies focus on broad topics, including comparisons of the diversity patterns between wild and cultivated Sorghum bicolor [ 8 ], identification of introduction events of Ambrosia artemisiifolia [ 7 ], verification of interspecific gene flow in Helianthus [ 9 ], and assessment of the genetic diversity and structure of numerous endangered species [ 10 – 12 ]. In particular, genetic diversity and structure, as indicators of gene flow, genetic drift, and differentiation, are essential to understanding the relationships within and among populations.…”