DNA Barcoding of Focal Plant Taxa

Bulbophyllum levinei (Photo © Dr Pankaj Kumar). This is part of DNA barcoding of Hong Kong orchids project.

Species evolve from one another through the accumulation of differences in their DNA. Knowledge of how these genetic differences distinguish groups of similar species allows researchers and conservation practitioners to unequivocally identify plants. Firstly, a plant specimen must be positively identified by observing the characteristics of flowers, leaves and other parts. Then, the sequence of base pairs in a series of candidate genetic regions is read from a small leaf sample removed from the specimen, and this genetic sequence data is stored in a database. Once sequence data from many positively identified species has been compiled, the database serves as a permanent reference library for the genetic differences that distinguish different species. In future, if a plant is collected and, for whatever reason, cannot be positively identified using morphology alone, rapid and highly accurate identification can be achieved by sequencing the same genetic regions and matching them to existing sequences in the database.

This approach has many advantages, including:

  • Only a minute tissue sample is required, so sampling need not be destructive.
  • Species that look similar can be readily resolved using unequivocal genetic information.
  • Plant specimens lacking flowers, and even processed plant parts, can still be positively identified.

The sequence of base pairs in just one or a few genetic regions is usually sufficient for resolving even very closely related species. This approach, known as DNA barcoding, is gaining popularity around the world as a powerful tool for species identification. In addition, species new to science can be highlighted as such because they will not match any existing record in the database. It is also useful in monitoring the illegal trade in protected wildlife, since species are usually transported in a processed form (such as medicines or other products) and are therefore usually extremely difficult to positively identify by direct observation.

Once we have positively identified a plant we can start to make decisions regarding a possible conservation action plan, which may involve working with the Hong Kong or mainland Government to enhance legal protection and monitoring of the forest containing rare plants.