The interior Southeastern United States could contain novel germplasm for the bioenergy crop switchgrass due to its diverse habitats and geographic location between genetic subpopulations (Atlantic, Midwest, and Gulf). Collections from this region could accelerate breeding progress, contribute to conservation efforts, and improve understanding of isolated grasslands in the region. This study located 22 sites in the Midsouth region and obtained 1,521,210 single nucleotide polymorphism markers of 202 individuals through genotype-by-sequencing. Individuals were evaluated for flowering time, winter survival and tiller number. Comparison to a national diversity panel revealed that branches of two major subpopulations occur in the region with two levels of polyploidy: Atlantic tetraploids and Midwest octoploids. Two locations contained admixed octoploid individuals with Midwest and Gulf genetics. Field performance of the Midwest octoploids conformed with prior reported performance of the Midwest subpopulation, although three sites contained promising late flowering traits. The Atlantic tetraploids had moderate winter survival, short stature, and anomalously early flowering. Atlantic populations mostly occurred in marginal sites and their morphological and flowering time adaptations may be a resource conservation strategy. Demographic inference of historical effective population size variation in a subset of tetraploid locations indicated a widespread recent decline in effective population size. This pattern is consistent with isolation of these switchgrass communities from larger populations and is further supported by evidence of inbreeding within the populations (F_I = 0.18). The populations documented in this study contain novel genetic diversity and adaptations to a range of marginal habitats. Therefore, this study provides a new source of germplasm for future breeding and conservation programs.

由于其多样化的栖息地和遗传亚群（大西洋、中西部和海湾）之间的地理位置，美国东南部内陆可能包含生物能源作物柳枝稷的新种质。来自该地区的收集品可以加速育种进程，有助于保护工作，并提高对该地区孤立草原的了解。本研究定位于中南部地区的22个位点，通过基因型测序获得202个个体的1,521,210个单核苷酸多态性标记。评估个体的开花时间、冬季存活率和分蘖数。与国家多样性小组的比较表明，该地区出现了两个主要亚群的分支，具有两个多倍体水平：大西洋四倍体和中西部八倍体。两个位置包含具有中西部和海湾遗传学的混合八倍体个体。中西部八倍体的田间表现与先前报道的中西部亚群的表现一致，尽管三个地点包含有希望的晚花性状。大西洋四倍体的冬季存活率适中，身材矮小，开花异常早。大西洋种群大多出现在边缘地点，它们的形态和开花时间适应性可能是一种资源保护策略。四倍体位置子集中的历史有效种群规模变化的人口统计学推断表明，近期有效种群规模普遍下降。_I  = 0.18）。本研究中记录的种群包含新的遗传多样性和对一系列边缘栖息地的适应性。因此，本研究为未来的育种和保护计划提供了新的种质来源。