Abstract
BackgroundLarge-scale plant diversity inventories are critical to develop informed conservation strategies. However, the workload required for classic taxonomic surveys remains high and is particularly problematic for megadiverse tropical forests.Methodology/Principal FindingsBased on a comprehensive census of all trees in two hectares of a tropical forest in French Guiana, we examined whether plant DNA barcoding could contribute to increasing the quality and the pace of tropical plant biodiversity surveys. Of the eight plant DNA markers we tested (rbcLa, rpoC1, rpoB, matK, ycf5, trnL, psbA-trnH, ITS), matK and ITS had a low rate of sequencing success. More critically, none of the plastid markers achieved a rate of correct plant identification greater than 70%, either alone or combined. The performance of all barcoding markers was noticeably low in few species-rich clades, such as the Laureae, and the Sapotaceae. A field test of the approach enabled us to detect 130 molecular operational taxonomic units in a sample of 252 juvenile trees. Including molecular markers increased the identification rate of juveniles from 72% (morphology alone) to 96% (morphology and molecular) of the individuals assigned to a known tree taxon.Conclusion/SignificanceWe conclude that while DNA barcoding is an invaluable tool for detecting errors in identifications and for identifying plants at juvenile stages, its limited ability to identify collections will constrain the practical implementation of DNA-based tropical plant biodiversity programs.
Highlights
The Neotropics hold an estimated 78,800 flowering plant species, over a third of the world’s total [1]
Tropical forests are being degraded at a fast pace [2,3], and over half of the estimated 11,000 Amazonian tree species may face a direct risk of extinction [4]
The lowest sequencing success was obtained with internal transcribed spacer (ITS), which amplified in only 41% of our samples
Summary
The Neotropics hold an estimated 78,800 flowering plant species, over a third of the world’s total [1]. Based on traditional botanical sampling, they were able to identify 97% of the sampled stems to the genus, and counted a total of 435 tree genera. In their statistical analyses, they decided to conservatively exclude the genera that were difficult to identify in the field when only sterile material was available. Their choice of excluding no less than 20.7% of the genera, and 15.7% of the sampled stems resulted in loss of information, the influence of which on their conclusions is unknown. Large-scale plant diversity inventories are critical to develop informed conservation strategies. The workload required for classic taxonomic surveys remains high and is problematic for megadiverse tropical forests
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