Phylogenetic Relationships among North American Grouse Inferred from Restriction Endonuclease Analysis of Mitochondrial DNA

Systematic relationships among North American grouse and ptarmigans (Tetraoninae) are not well defined because traditional classifications were based on morphological and behavioral characters with limited taxonomic utility. Restriction enzyme analysis of mitochondrial DNA (mtDNA) was used to generate a phylogeny for North American tetraonines that was then utilized to test previous phylogenetic hypotheses for the group and to examine the origin and evolution of complex reproductive behaviors and morphological features characteristic of grouse and ptarmigan species. Nucleotide sequence divergence among congeneric species derived from mtDNA restriction fragment patterns varied extensively, ranging from 0.28% in prairie grouse (Tympanuchus) to 4.06% among ptarmigans (Lagopus) and 10.15% between Blue Grouse (Dendragapus obscurus) and Spruce Grouse (D. canadensis). Using the Northern Bobwhite (Colinus virginianus) as an outgroup, the molecular phylogeny partitioned species into three primary groups: (1) Tympanuchus; (2) Lagopus, Dendragapus obscurus, and Tetrao urogallus (the European Capercaillie); and (3) the Ruffed Grouse (Bonasa umbellus), Dendragapus canadensis, and Sage Grouse (Centrocercus urophasianus). Prairie grouse were genetically distinct from other grouse species, but a polyphyletic distribution of haplotypes and limited mtDNA differentiation within Tympanuchus suggest that divergence among the prairie grouse occurred very recently. Within Lagopus, the Willow (L. lagopus) and Rock (L. mutus) Ptarmigans were more closely related to each other than either was to the White-tailed Ptarmigan (L. leucurus). Dendragapus canadensis grouped with Bonasa umbellus; whereas D. obscurus was allied with Lagopus and Tetrao. Thus, the genus Dendragapus as currently constructed is polyphyletic (i.e., D. canadensis and D. obscurus have had separate evolutionary histories) and the morphological similarities between the two species may be attributable to convergent adaptation to coniferous forest. We inferred from the molecular phylogeny that the complex reproductive systems in tetraonines have arisen independently and that corresponding morphological and behavioral specializations may reflect parallel evolutionary trends.