Abstract
DNA barcoding is widely used in species identification, but there is considerable controversy regarding the extent of sampling in research methods. Some scholars have proposed that this small sample size underestimates the intraspecific genetic diversity, which would impact on the accuracy of DNA barcoding to identify species. In study, we selected all Phellodendron species (including P. amurense Rupr., P. chinense Schneid., and P. chinense var. glabriusculum Schneid.) as the materials, collected 59 P. amurense samples from 35 populations greatly to represent the genetic diversity, and analyzed the haplotype, genetic distance, barcoding gap, and Neighbor-Joining (NJ) trees based on psbA-trnH and internal transcribed spacer gene sequences. Additionally, a sampling simulation was conducted to assess the correlation between genetic diversity and the number of populations. Finally, analysis of critical geographical populations was performed. Based on analysis of haplotype, genetic distance, barcoding gap, and NJ trees, we found that eight P. amurense samples impacted on the effectiveness of DNA barcoding, which genetic information were very important to identify Phellodendron species. Moreover, the result of the NJ tree analysis performed the small-scale P. amurense sample size did not completely match the objective phylogenetic relationship in Phellodendron. In simulation sampling analysis, the data showed the genetic diversity indexes at the same population level gradually decreased and stabilized as the number of simulation sampling populations increased. We found that 1-2 samples from over 24 populations based on uniform geographical distribution could represent 80% of the genetic diversity of P. amurense and ensure authenticity and reliability of DNA barcoding. Thus, we proposed it is particularly important adequately samples to cover infraspecific genetic diversity in order to ensure identification accuracy of DNA barcoding.