COI flags a recent radiation in passerine birds

CAMPAGNA, LEONARDO; LIJTMAER, DARÍO A.; LOUGHEED, STEPHEN C.; TUBARO, PABLO L.

Mexico, D.F.

Congreso; Third International Barcode of Life Conference; 2009

Insituto de Biología, UNAM and Consoritum for the Barcode of Life

The capuchinos comprise a group of 11 Sporophila species with little morphological differentiation, extended sympatry, and marked sexual dimorphism in both color patterns and vocalizations. Our previous work using mitochondrial DNA (partial cytochrome b and COII-Tlys-ATP8 fragments) suggested that the capuchinos are monophyletic and further divided into two clades: northern capuchinos (2 species) and southern capuchinos (9 species). The phylogenetic relationships among the southern capuchinos were unresolved due to lack of reciprocal monophyly among species. The objective of the present study was to clarify the phylogenetic relationships of the capuchinos using an augmenting data set of DNA sequences. In total we sequenced 4.2 kb (cytochrome b, cytochrome c oxidase 1 (COI), mitochondrial control region and 2 nuclear pseudogenes: numt2 and numt3) and genotyped 191 samples for 6 DNA microsatellite loci. We included COI to permit us to evaluate its efficacy in diagnosing species within this challenging group. We subjected the sequences to neighbour joining, maximum parsimony and Bayesian phylogenetic analyses and estimated levels of differentiation among species using frequency-based analyses of microsatellites. We found that the southern capuchinos share COI haplotypes and show extremely low interspecific divergence constituting the only example of several avian species that cannot be separated among the neotropical birds barcoded thus far. No further insight into the phylogenetic relationships of the group was obtained with the remaining markers, suggesting that the lack of resolution using COI is due to the unique evolutionary history of the southern capuchinos rather than to limitations of this molecular marker. Our results flag the southern capuchinos as a new case of an explosive and recent radiation where incomplete lineage sorting and hybridization with introgression are the most likely causes for the observed genetic pattern.