Taxonomy of the bean goose-pink-footed goose.

The bean goose Anser fabalis and the pink-footed goose A. brachyrhynchus breed in the tundra and taiga zones of Eurasia and eastern Greenland, and the taxonomy of the group based on morphology has been controversial. We investigated the phylogenetic relationships within the bean goose-the pink-footed goose complex using mitochondrial control region sequences of 199 individuals collected from the breeding areas in the Palaearctic and Eastern Nearctic. We found three mitochondrial clades geographically distributed to (1) Greenland, Iceland and Svalbard (A. brachyrhynchus), (2) the eastern taiga zone (former subspecies A. fabalis middendorffii), and (3) the western taiga and the tundra zone (subspecies A. fabalisrossicus, serrirostris and fabalis). MtDNA phylogeny suggests that morphological affinities between the taxa, e.g. in the bill structure, result from convergent evolution due to adaptation to similar habitats. Although a latitudinal cline in morphology was observed, clear phylogenetic discontinuities exist in the taiga and tundra zones supporting a species status for brachyrhynchus and middendorffii.