DNA Barcoding in Euphorbia Species: Current Status, Challenges, and Future Perspectives

Abstract

The genus Euphorbia L., one of the largest genera within the family Euphorbiaceae, comprises approximately 2,000– 2,200 species distributed across diverse ecological regions worldwide. Owing to its extensive morphological diversity, phenotypic plasticity, convergent evolution, and complex taxonomic relationships, accurate species identification within the genus remains a significant challenge. Traditional morphological approaches are often insufficient for distinguishing closely related species, particularly when diagnostic characters are absent or highly variable. In this context, DNA barcoding has emerged as a powerful molecular tool for species identification, taxonomic clarification, biodiversity assessment, and conservation research. This review provides a comprehensive overview of DNA barcoding applications in Euphorbia, with emphasis on the major barcode markers used in plant identification, including chloroplast loci (rbcL, matK, trnH-psbA, and ycf1) and nuclear markers (ITS and ITS2). The principles, methodology, and effectiveness of these markers are discussed, along with their roles in species discrimination, detection of cryptic species, authentication of medicinal plants, phylogenetic reconstruction, and biodiversity conservation. Comparative evaluation of barcode markers indicates that while rbcL and matK remain the standard core plant barcodes, nuclear ITS regions generally provide higher species-level resolution. Emerging markers such as ycf1 and multilocus barcode combinations have demonstrated improved discriminatory power in taxonomically complex groups. Despite significant progress, several challenges continue to limit the effectiveness of DNA barcoding in Euphorbia, including low genetic divergence among closely related species, hybridization, polyploidy, incomplete reference databases, and technical constraints associated with molecular analyses. Recent advances in DNA metabarcoding, genome skimming, chloroplast genome sequencing, next-generation sequencing technologies, and integrative taxonomy offer promising solutions to these limitations and are expected to enhance future taxonomic and evolutionary studies. Overall, DNA barcoding has substantially improved species identification and systematic research in Euphorbia. Continued development of comprehensive reference databases, adoption of multilocus and genomic approaches, and integration of molecular and morphological data will further strengthen taxonomic resolution and contribute to the conservation and sustainable utilization of Euphorbia diversity worldwide.