Federally endangered Xyris tennesseensis is a perennial monocot found in imperiled wetlands such as calcareous seeps and riparian habitats within its disjunct distribution (one county in Tennessee, three in Alabama and four in Georgia). This species belongs to a genus of wetland plants for which very little genetic work has been carried out. Because of the rarity of this species, we hypothesized that it would have low genetic variability overall and that populations were likely to be genetically differentiated due to the species’ disjunct distribution. Fourteen microsatellite loci polymorphic at the species level showed limited variability at the population level, averaging 16.3% polymorphic loci, 1.17 alleles per locus, an observed heterozygosity of 0.017, and an expected heterozygosity of 0.054. The discrepancy between observed and expected heterozygosity resulted in a relatively high F_IS of 0.71, suggesting that X. tennesseensis experiences high levels of inbreeding. We also found evidence of varying levels of vegetative reproduction in this species. Analysis of molecular variance estimated that differentiation among the regions (states) accounted for the majority (60%) of the genetic variation in this species, with an additional 31% due to genetic differences among the populations of each state and only 9% due to variability within populations. These data indicate X. tennesseensis possesses low levels of genetic diversity and experiences virtually no gene flow among populations. To preserve the genetic diversity of this species, multiple populations must be protected, with priority given to the largest and most variable populations in each region.

受联邦威胁的田纳西草是多年生的单子叶植物，分布在分散的分布区（田纳西州的一个县，阿拉巴马州的三个县和佐治亚州的四个县）内的石灰质渗漏和河岸生境等濒危湿地中。该物种属于湿地植物的属，对其进行的遗传工作很少。由于该物种的稀有性，我们假设它总体上具有较低的遗传变异性，并且由于该物种的不连续分布，很可能在种群上进行了遗传分化。物种水平上的14个微卫星基因座多态性显示出有限的变异性，平均水平为16.3％多态性基因座，每个基因座1.17个等位基因，观察到的杂合度为0.017，预期的杂合度为0.054。观察到的和预期的杂合性之间的差异导致相对较高F _IS为0.71，表明X. tennesseensis经历了高水平的近交。我们还发现了该物种营养繁殖水平不同的证据。分子变异分析估计，地区（州）之间的差异占该物种遗传变异的大部分（60％），另外31％是由于各州种群之间的遗传差异，而只有9％是由于群体内部的变异性。这些数据表明X. tennesseensis拥有低水平的遗传多样性，几乎没有群体间的基因流动。为了保护该物种的遗传多样性，必须保护多个种群，其中优先考虑每个区域中最大，变化最大的种群。