Ultra-Barcoding Discovers a Cryptic Species in (Melanthiaceae), a Medicinally Important Plant.

Ultra-barcoding is a technique using whole plastomes and nuclear ribosomal DNA (nrDNA) sequences for plant species identification. is a medicinal plant of great economic importance for the pharmaceutical industry. However, the alpha taxonomy of is still uncertain, hindering effective conservation and management of the germplasm. To resolve long-standing taxonomic disputes regarding this species, we newly generated the complete plastomes and nrDNA sequences from 22 accessions. Ultra-barcoding analyses suggest that as currently circumscribed is made up of two distinct genetic lineages, corresponding to the two phenotypes ("typical" and "high stem" form) identified early in our study. With distinct morphologies and distribution, the "high stem" form should be recognized as a previously unrecognized species; here it is described as a new species, sp. nov. Moreover, the ultra-barcoding data do not support treatment of as a conspecific variety under . Our study represents a guiding practical application of ultra-barcoding for discovery of cryptic species in taxonomically challenging plant taxa. The findings highlight the great potential of ultra-barcoding as an effective tool for resolving perplexing problems in plant taxonomy.