DNA Barcoding Reveals Cryptic Diversity and Informs Conservation Priorities in Chinese <i>Firmiana</i> Species (Malvaceae) Using Genome Skimming Data

ABSTRACT Accurate species delineation is crucial for biodiversity conservation. The genus Firmiana Marsili (Malvaceae) comprises deciduous trees and shrubs, many of which are rare and endangered in China, underscoring the urgent need for effective conservation measures. However, morphological similarities among closely related Firmiana species complicate taxonomic identification, and traditional morphology‐based approaches are often insufficient for taxa with complicated evolutionary histories. To address this, we conducted genome skimming on 62 Firmiana samples representing all 10 recognized Chinese species and two unidentified taxa, assembling plastome and nuclear ribosomal DNA sequences. We evaluated the effectiveness of super‐barcodes (plastid genomes and nrDNA), plastid hyper‐variable barcodes, and four universal barcodes. Our results show that nrITS exhibited the highest discriminatory power, successfully identifying all 10 recognized Firmiana species, and is thus recommended as the primary barcode for the genus. In addition, two cryptic lineages were discovered within the Firmiana major complex. These results provide critical insights for the conservation, management, and sustainable use of endangered Firmiana species. This study underscores the urgent need to revise species boundaries within the F. major complex, and highlights the potential of DNA barcoding as an efficient tool for species identification and conservation of the genus Firmiana .