Phylogeny
The genus Phasianus is a member of the clade of 6 genera known as the gallophesants, which are usually placed as the crown taxa of the family Phasianidae. Phasianidae also includes certain quails and partridges, as well as turkeys.
Phasianus shares its most recent common ancestor with the genera Lophura (firebacks, Edwards’s pheasant, silver pheasant, and allies ) Crossoptilon (eared pheasants), and Catreus (cheer pheasant), and is sympatric with many species in these genera.
Phylogeny within Phasianus has been mapped using a combination of mitochondrial DNA and Nuclear DNA, with an emphasis on cytochrome complexes. These sequences were compared and made into phylogenetic trees using maximum likelihood and Bayesian inferences.
Phylogenetic analyses done on separate occasions have shown Phasianus versicolor (green pheasant) as distinct, which is generally unsurprising due to its geographic isolation from and different plumage color than other Phasianus pheasants. However, within Phasianus colchicus (ring-necked pheasant) certain strange and unexpected patterns have been found.
Traditionally, the 30 extant subspecies of ring-necked pheasants have been divided up into 5 groups based on plumage color and geographic range. These groups of five are the black-necked (colchicus) (4 ssp.), white-winged (principalis-chrysomela) (6 ssp.), Tarim (tarimensis) (1 ssp.), Mongolian (mongolicus) (2 ssp.) although the group does not occur in Mongolia, and gray-rumped (torquatus) (17 ssp.) groups.
figure modified from Birds of the World.
However, modern phylogenetic analysis shows that based on genetics, as well as plumage and geographic range, there should instead be 8 groupings of subspecies, and possibly a split of the ring-necked pheasant into 3 distinct species.
The subspecies elegans has been shown to be an outgroup to all other ring-necked pheasants, and based on molecular clocks, is the ancestral condition. This also likely means that the range of elegans is ancestral as well. If elegans is not its own species (which it very well might be) then it likely deserves to be in its own subspecies grouping. However, genetic evidence has also changed the traditional ring-necked pheasant grouping in other ways. The most comprehensive study of ring-necked pheasant phylogeny has changed the number of subspecies groups from five to eight by splitting up the “torquatus” group.
Figure modified from Birds of the World and Liu. et.al 2020
Of the subspecies groups, three greater lineages could be identified, Liu et. al suggest these three lineages could be classified as species. However, this has not been generally supported by the ornithological community in general due to the results being from only a single paper.
The three suggested species-level lineages are:
The Yunnan pheasant, comprising the elegans outgroup
The Chinese pheasant, comprising the torquatus, strauchi–vlangallii and formosanus groups
The Turkestan pheasant, comprising the tarimensis, principalis–chrysomelas, mongolicus and colchicus groups
Based on the phylogeny and molecular clocks found in these groups, we can infer that the ancestral population was closest to elegans, which over the Pleistocene migrated across Asia, making it to Japan to eventually become the green pheasant, and eventually migrating over millions of years until the complex reached Europe and Siberia.
Phylogenetic tree from Liu et.al 2020:
References:
Giudice, John H., et al. “Ring-Necked Pheasant (Phasianus Colchicus), Version 1.1.” Birds of the World, 2022. birdsoftheworld.org, https://doi.org/10.2173/bow.rinphe1.01.1.
Hosner, Peter A., et al. “Phylogeny and Diversification of the Gallopheasants (Aves: Galliformes): Testing Roles of Sexual Selection and Environmental Niche Divergence.” Zoologica Scripta, vol. 49, no. 5, Sept. 2020, pp. 549–62. DOI.org (Crossref), https://doi.org/10.1111/zsc.12441.
Kayvanfar, Nasrin, et al. “Phylogeography of the Common Pheasant Phasianus Colchicus.” Ibis, vol. 159, no. 2, Apr. 2017, pp. 430–42. DOI.org (Crossref), https://doi.org/10.1111/ibi.12455.
Liu, Simin, et al. “Regional Drivers of Diversification in the Late Quaternary in a Widely Distributed Generalist Species, the Common Pheasant Phasianus Colchicus.” Journal of Biogeography, vol. 47, no. 12, Dec. 2020, pp. 2714–27. DOI.org (Crossref), https://doi.org/10.1111/jbi.13964.
Zhang, Lixun, et al. “Phylogeography-Based Delimitation of Subspecies Boundaries in the Common Pheasant (Phasianus Colchicus).” Biochemical Genetics, vol. 52, no. 1–2, Feb. 2014, pp. 38–51. DOI.org (Crossref), https://doi.org/10.1007/s10528-013-9626-5.
Header Image credit: Ryan Crane, ebird.