All birds barcoding initiative (ABBI): building an atlas of avian mitochondrial DNA diversity

STOECKLE, MARK Y.; BAKER, ALLAN J.; KERR, KEVIN C. R.; LIFJELD, JAN T.; LIJTMAER, DARÍO A.; ERICSON, PER; TUBARO, PABLO L.

Adelaida

Congreso; Fourth International Barcode of Life Conference; 2011

Consortium for the Barcode of Life y University of Adelaide

As of May 2011, researchers have deposited over 25,000 barcode records representing over 3,800 species, more than 1/3 of world birds. Results so far strongly confirm the early observation that most bird species are comprised of a single cluster of mtDNA, distinct from those of other species. Discordant cases appear to reflect very young species or hybridization among recently diverged species. About 20% of avian species comprise two or more mtDNA clusters that differ by geographic range. The proportion of such species is greatest outside of northern North America and Europe. Extrapolating from current taxonomic practice predicts that most such clusters will eventually be recognized as distinct species. Many higher-level groupings are visible as discontinuities in a Klee diagram of COI sequences. Together with species-level clustering this suggests that COI barcodes could enable a draft taxonomy for unstudied groups and might help with revision of better-studied groups, including birds. Mitochondrial diversity is weakly-related to census population size, which reflects geographically-structured variation in some more abundant birds and restricted variation in the rarest. Nearly all fixed differences between species/clusters are synonymous, while the much rarer intraspecific/intracluster variants are disproportionately nonsynonymous. Even among modest-sized sets of closely-related species, most synonymous sites are occupied by fixed differences. The findings imply reproductively-isolated populations undergo continuous change in the mitochondrial genome through genetic drift. A persistent scientific challenge for avian taxonomy is drawing the line between what are considered distinctive populations and what are considered nascent or submerging species, and a major practical challenge is describing the very large number of overlooked species from understudied regions. The growing ABBI atlas of avian mitochondrial diversity can help highlight the former and speed the latter.