The Barcode Blog

A mostly scientific blog about short DNA sequences for species identification and discovery. I encourage your commentary. -- Mark Stoeckle

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1/1000 animal diversity mapped

F1large2In 16 December 2009 Biol Lett, researchers from University of Guelph, University of British Columbia, and Agriculture and Agri-Food Canada report on COI barcodes for 11,289 individuals representing 1,327 species of Lepidoptera (moths and butterflies) collected in eastern North America. This large collection revealed the same patterns of highly restricted intraspecific variation, uncommon barcode sharing, and overlooked diversity seen in numerous smaller studies: average variation within species was 0.43%, while average among congeneric species was 7.7%, 18-fold higher. Only nine cases (0.7%) of barcode sharing between species were observed, and at the same time, large divergences (>2%) suggesting overlooked taxa were found in 67 (5.1%) of cases (in some cases morphological and ecological differences supporting species status were observed). The survey included multiple individuals per species collected at sites 500 to 2800 km apart, with “no significant increase in genetic distances with geographical separation.” Hebert, deWaard, and Landry conclude “an effective identification system can be constructed for the Lepidoptera fauna of eastern North American without extensive geographical surveys of each species,” and that, given likely similar patterns in most terrestrial and marine fauna, “a comprehensive barcode library for animal life can be assembled rapidly,” with diverse benefits to society and science.

In my view, this study should lay to rest the early and persisting worries of some taxonomists that single gene DNA barcoding would distinguish species only in limited situations. For example, in a 2004 PLoS Biol commentary, Moritz and Cicero cautioned “But to determine when and where [DNA barcoding]…is applicable, we now need to discover the boundary conditions.” The 2009 answer is that there are no major restrictions to wide application of DNA barcoding in animals, taxonomically or geographically, and the one regularly encountered limitation is very young species, which represent a small fraction of recognized taxa even in intensively studied groups. At the same time DNA barcoding speeds taxonomic assessment by flagging genetically distinct forms, many of which are found represent unrecognized species, including species that would likely otherwise remain hidden indefinitely. Together with prior work this study refutes a widely-cited (pre-barcoding) estimate that 23% of animal taxa have shared or overlapping mitochondrial DNA sequences (Funk and Omland Ann Rev Genet 2003); this estimate presumably reflected biases in then-existing databases. In closing, I note that Hebert, deWaard, and Landry offer a new yardstick, namely the fraction of the animal kingdom mapped, lifting our eyes up to the goal of a rapid identification system for all eukaryotic life.

This entry was posted on Thursday, December 24th, 2009 at 3:49 pm and is filed under General. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

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About this site

This web site is an outgrowth of the Taxonomy, DNA, and Barcode of Life meeting held at Banbury Center, Cold Spring Harbor Laboratory, September 9-12, 2003. It is designed and managed by Mark Stoeckle, Perrin Meyer, and Jason Yung at the Program for the Human Environment (PHE) at The Rockefeller University.

About the Program for the Human Environment

The involvement of the Program for the Human Environment in DNA barcoding dates to Jesse Ausubel's attendance in February 2002 at a conference in Nova Scotia organized by the Canadian Center for Marine Biodiversity. At the conference, Paul Hebert presented for the first time his concept of large-scale DNA barcoding for species identification. Impressed by the potential for this technology to address difficult challenges in the Census of Marine Life, Jesse agreed with Paul on encouraging a conference to explore the contribution taxonomy and DNA could make to the Census as well as other large-scale terrestrial efforts. In his capacity as a Program Director of the Sloan Foundation, Jesse turned to the Banbury Conference Center of Cold Spring Harbor Laboratory, whose leader Jan Witkowski prepared a strong proposal to explore both the scientific reliability of barcoding and the processes that might bring it to broad application. Concurrently, PHE researcher Mark Stoeckle began to work with the Hebert lab on analytic studies of barcoding in birds. Our involvement in barcoding now takes 3 forms: assisting the organizational development of the Consortium for the Barcode of Life and the Barcode of Life Initiative; contributing to the scientific development of the field, especially by studies in birds, and contributing to public understanding of the science and technology of barcoding and its applications through improved visualization techniques and preparation of brochures and other broadly accessible means, including this website. While the Sloan Foundation continues to support CBOL through a grant to the Smithsonian Institution, it does not provide financial support for barcoding research itself or support to the PHE for its research in this field.