Assessing candidate DNA barcodes for Chinese and internationally traded timber species

Accurate identification of species from timber is an essential step to
help control illegal logging and forest loss. However, current approaches
to timber identification based on morphological and anatomical
characteristics have limited species resolution. DNA barcoding is a proven
tool for plant species identification, but there is a need to build
reliable reference data across broad taxonomic and spatial scales. Here,
we construct a species barcoding library consisting of 1,550 taxonomically
diverse timber species from 656 genera and 124 families, representing a
comprehensive genetic reference data set for Chinese timber species and
international commercial traded timber species, using four barcodes (rbcL,
matK, trnH–psbA, and ITS2). The ITS2 fragment was found to be the most
efficient locus for Chinese timber species identification among the four
barcodes tested, both at the species and genus level, despite its low
recovery rate. Nevertheless, the barcode combination matK+trnH–psbA+ITS2
was required as a complementary barcode to distinguish closely related
species in complex datasets involving internationally traded timber
species. Comparative analyses of family-level discrimination and
species/genus ratios indicated that the inclusion of closely related
species is an important factor affecting the resolution ability of
barcodes for timber species verification. Our study indicates that
although nuclear ITS2 is the most efficient single barcode for timber
species authentication in China, complementary combinations like
matK+trnH–psbA+ITS2 are required to provide broader discrimination power.
These newly-generated sequences enrich the existing publicly available
databases, especially for tropical and subtropical evergreen timber trees
and this current timber species barcode reference library can serve as an
important genetic resource for forestry monitoring, illegal logging
prosecution and biodiversity projects.