Since the 1980s, the aquatic fern Ceratopteris richardii has been used as a model organism for genetic and developmental studies. Recently, a draft whole genome for the species was completed. While there has been a great deal of research done on C. richardii, our knowledge of the other species in the genus remains depauperate. Systematists have described the genus as having from one to over half a dozen species and varieties. Considerable morphological variation exists within described species as well as speculated hybridization between species. Due to its increasing use as a model system, a solid taxonomic and systematics understanding of the group is critical. In this study, we begin to unravel the complexity of the species relationships between the species of Ceratopteris. We used double digest restriction-site associated DNA sequencing on 60 samples, representing all currently recognized species, collected from herbarium specimens from around the world. We are exploring polyploidy, hybridization, and genetic relationships. This work is led by Sylvia Kinosian as part of her PhD research.