DNA barcoding the flowering plants from the tropical coral islands of Xisha (China)

DNA barcoding has been widely applied to species diversity assessment in various ecosystems, including temperate forests, subtropical forests, and tropical rain forests. However, tropical coral islands have never been barcoded before due to the difficulties in field exploring. This study aims at barcoding the flowering plants from a unique ecosystem of the tropical coral islands in the Pacific Ocean and supplying valuable evolutionary information for better understanding plant community assembly of those particular islands in the future.

Xisha Islands, China.

This study built a DNA barcode database for 155 plant species from the Xisha Islands using three DNA markers (ITS, rbcL, and matK). We applied the sequence similarity method and a phylogenetic-based method to assess the barcoding resolution.

All the three DNA barcodes showed high levels of PCR success (96%-99%) and sequencing success (98%-100%). ITS performed the highest rate of species resolution (>95%) among the three markers, while plastid markers delivered a relatively poor species resolution (85%-90%). Our analyses obtained a marginal increase in species resolution when combining the three DNA barcodes.

This study provides the first plant DNA barcode data for the unique ecosystem of tropical coral islands and considerably supplements the DNA barcode library for the flowering plants on the oceanic islands. Based on the PCR and sequencing success rates, and the discriminatory power of the three DNA regions, we recommend ITS as the most successful DNA barcode to identify the flowering plants from Xisha Islands. Due to its high sequence variation and low fungal contamination, ITS could be a preferable candidate of DNA barcode for plants from other tropical coral islands as well. Our results also shed lights on the importance of biodiversity conservation of tropical coral islands.