Botanists from all over the world have convened in New York City and are hammering out plans to assemble a DNA-based catalog of the Earth's tree species.

The scientists met yesterday (May 1) and are meeting today (May 2) at the New York Botanical Garden to discuss an effort to barcode - or identify using short, standardized stretches of genetic material - all 100,000 or so tree species on the planet. The project is called Tree-BOL, for the tree barcode of life, and will join the ranks of similar efforts, such as FISH-BOL and ABBI (All Birds Barcoding Initiative), seeking to catalog Earth's biodiversity.

There is, however, a catch to barcoding plants. While most animal species can be barcoded and differentiated on the species level using a universal stretch of DNA - the CO1 mitochondrial gene - plants, with their variable speciation rates and habit of hybridizing, show little variation in CO1 sequences across different taxa. For this reason, plant barcoders have focused on combinations of chloroplast genes, nuclear markers, and non-coding regions of DNA to serve as the plant barcode.

When I attended the plant working group meeting at the Second International Barcode of Life Conference in Taiwan last year, agreement on which markers should be used as a plant DNA barcode was elusive. The group seems to be closer to consensus now. "A lot of that is being discussed at this moment. My sense is that they're making progress," said New York Botanical Garden spokesman George Shakespear when I called him today during the meeting.

Shakespear also told me that Tree-BOL is being launched thanks to a $572,000, 24-month grant from the Alfred P. Sloan foundation, which has made contributions to other large-scale barcoding efforts.