Date of Thesis

Spring 2021


Chasmanthium latifolium (Michx.) Yates (Poaceae) is a loosely colonial, rhizomatous, perennial grass species that lives in riparian habitats, making it fittingly referred to as river oats. Native to the southern Midwest and the eastern half of the United States, C. latifolium reaches the northeastern edge of its range in Pennsylvania. Within Pennsylvania, eleven extant C. latifolium populations are found along four waterways: the Monongahela River, the Susquehanna River, and two tributaries to the Susquehanna River. This limited state distribution exhibits an east-west disjunct distribution, where western populations are largely separated from eastern populations with one centrally located population. Between the limited distribution and number of remaining populations as well as habitat threats, C. latifolium is considered critically imperiled (S1) at the state-level by the Pennsylvania Natural Heritage Program. While western populations appear contiguous with the core distribution, central and eastern populations are separated by the Allegheny Mountain range with large distances between populations along the Susquehanna River. Because of these conservation concerns, a better understanding of the natural history and genetics of C. latifolium should prove useful for conservation practitioners. My research aims to investigate the genetic diversity and connectivity of the critically imperiled taxon to better understand the natural history of the species and develop scientifically informed conservation practices. This work utilizes a genotyping by sequencing (GBS) approach to generate genomic data for use in population genetics analyses. I found that all populations appear to be genetically healthy, with high levels of heterozygosity and no inbreeding. Western populations appear as one genetic unit with some sub-structuring, while central-eastern populations are genetically different from western populations and other populations along the Susquehanna River system. Although there is currently no evidence of inbreeding, given the genetic isolation seen within the Susquehanna River populations, inbreeding may be of concern in the future. My research provides an updated, scientifically-informed conservation status assessment of C. latifolium in Pennsylvania. This project combines rare plant surveys done by the Pennsylvania Natural Heritage Program and Western Pennsylvania Conservancy with genetic work done at Bucknell University to address broad conservation questions.


river oats, rare species, population genomics, conservation, poaeceae, Chasmanthium

Access Type

Honors Thesis

Degree Type

Bachelor of Science



Minor, Emphasis, or Concentration


First Advisor

Christopher T. Martine

Second Advisor

Tanisha M. Williams

Third Advisor

Brian J. Smith


Fourth Advisor

Rachel Goad