Phylogeographic patterns in Motacilla flava and Motacilla citreola: Species limits and population history

We conducted phylogeographic analyses of Motacilla flava (Yellow Wagtail) and M. citreola (Citrine Wagtail). We analyzed mitochondrial DNA sequences from 167 M. flava specimens obtained from 17 localities throughout Eurasia and Alaska, and 38 specimens of M. citreola obtained from 7 Eurasian localities. Phylogenetic analysis revealed three clades within traditionally recognized M. flava: Europe and southwestern Asia, northeastern Eurasia, and southeastern Asia. Those groups should be considered species, because together they are not monophyletic, and are interspersed with M. citreola, M. cinerea, and M. alba. Motacilla citreola also is paraphyletic, consisting of two species-level groups. Northeastern and southeastern groups of M. flava each appear to be sister taxa to eastern and western groups of M. citreola, respectively. Together those four groups form a clade, whereas the western M. flava group is considerably more distant. Within each of the three groups of M. flava, and the two groups of M. citreola, little phylogeographic structure was detected. Signatures of past population expansion are evident for some populations of M. flava; expansion is more recent in Moscow, Kursk (western group), Yamal, and Anabar (northeastern group), and older in Tyva and Vyatka (western group). A history of population stability is inferred for the Yamal population of M. citreola. Nested-clade analyses detected contiguous range expansion for southeastern M. flava and restricted gene flow with isolation by distance for northeastern M. flava and eastern M. citreola.