Using complete cytochrome b sequence data, we determined that the genus Calcarius, as presently recognized, is paraphyletic. Calcarius plus Plectrophenax form a highly supported clade composed of two subclades, a "snow bunting" clade comprised of Plectrophenax plus Calcarius mccownii (formerly in the monotypic genus Rhynchophanes), and a "collared" longspur clade of Calcarius lapponicus, ornatus, and pictus. Contrary to conventional thought, Calcarius is not phylogenetically close to either Calamospiza or Emberiza. Unlike these two genera, the taxonomic affinities of Calcarius appear to lie outside of the sparrow (tribe Emberizini) assemblage. Calcarius appears to be a relatively old songbird lineage, originating between 4.2 and 6.2 million years ago. Within Calcarius, pictus and ornatus form a closely related sister pair (2.9% divergent), as do Calcarius nivalis and hyperboreus (0.18% divergent). The group (Calcarius, sensu lato) is inferred to have its origins at relatively high latitudes in the New World.
Bibliographical noteFunding Information:
We thank the Burke Museum of Natural History (UWBM below) for providing C. pictus and Fringilla coelebs tissue specimens and the Montana Department of Fish and Game for kindly issuing a collecting permit. A. Fry, T. Brashear, and G. Voelker provided valuable field assistance. KW received support from the National Science Foundation (OPP 9725154) to obtain P. hyperboreus samples in the Bering Sea. Lab funding was provided in part by an NSF Grant (DEB-9317945) to RMZ. Museum catalogue numbers for voucher specimens ( Table 2 ) are as follows: C. hyperboreus , UAM 7066; C. nivalis , BMNH 42136; C. lapponicus , BMNH 42531; C. mccownii , BMNH 42523; C. ornatus , BMNH 42528; C. pictus , UWBM [SAR7025]; F. coelebs , UWBM [BKS1615].