Molecular systematics of the scaled quail complex (Genus callipepla)

We obtained 1,040 bp of sequence from the mitochondrial DNA (mtDNA) genes cytochrome b (cyt b; 736 bp) and NADH-subunit 2 (ND2; 304 bp) to address phylogenetic relationships among the four species in the Scaled Quail complex. California Quail (Callipepla californica) and Gambel's Quail (C. gambelii) were sister taxa, whereas the relationships of the Elegant Quail (C. douglasii) and Scaled Quail (C. squamata) were unclear; they might be sister species, or Elegant Quail might be the sister to California plus Gambel's quails. A third, less-likely alternative predicts a contemporaneous origin of Elegant Quail, Scaled Quail, and the ancestor of California and Gambel's quail. The latter phylogenetic hypothesis, however, matches Hubbard's (1973) biogeographic model. Irrespective of which biogeographic hypothesis is correct, calibration of mtDNA genetic distances suggests that the speciation events are much older than the late Pleistocene dates given by Hubbard. Calibration of the rate of mtDNA (cyt b, ND2) evolution based on dating of fossil remains of the extinct species Cyrtonyx cooki suggested a rate of 2% per million years. Northern Bobwhite (Colinus virginianus), Mountain Quail (Oreortyx pictus), and Montezuma Quail (Cyrtonyx montezumae) were successively more distantly related to the Scaled Quail complex. Phylogenetic trees derived from allozymes (Gutierrez et al. 1983) and mtDNA sequences were topologically identical, suggesting that both types of gene trees recover the species tree.