Anas

Taxobox
name = "Anas"

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image_width = 250px
image_caption = Female Mallard ("Anas platyrhynchos") with brood of young, a typical member of this genus.
regnum = Animalia
phylum = Chordata
classis = Aves
subclassis = Neornithes
infraclassis = Neognathae
superordo = Galloanserae
ordo = Anseriformes
familia = Anatidae
subfamilia = Anatinae
genus = "Anas"
genus_authority = Linnaeus, 1758
subdivision_ranks = Species
subdivision = Some 40-50, but see text.

"Anas" is a genus of dabbling ducks. It includes mallards, wigeons, teals, pintails and shovelers in a number of subgenera. Some authorities prefer to elevate the subgenera to genus rank [Carboneras (1992)] . Indeed, as the moa-nalos are very close to this clade and may have evolved later than some of these lineages, it is rather the absence of a thorough review than lack of necessity that this genus is rather over-lumped.

ystematics

The phylogeny of this genus is one of the most confounded ones of all living birds. Research is hampered by the fact the radiation of the two major groups of "Anas" - the teals and mallard groups -; took place in a very short time and fairly recently, roughly in the mid-late Pleistocene. Furthermore, hybridization probably has long played a major role in "Anas" evolution, with within-subgenus hybrids regularly and between-subgenus hybrids not infrequently being fully fertile [Carboneras (1992); see also Mariana Mallard.] . The relationships between species are much obscured by this fact, and mtDNA sequence data is of dubious value in resolving their relationships [e.g. Kulikova "et al." (2005)] ; on the other hand, nuclear DNA sequences evolve too slowly to resolve the phylogeny of the subgenus "Anas" for example.

Some major clades can be discerned. For example, that the traditional subgenus "Anas", the mallard group, forms a monophyletic (in the loose sense, i.e. non-holophyletic) group has never been seriously questioned by modern science and is as good as confirmed (but see below). On the other hand, the phylogeny of the teals is very confusing.

It is fairly clear by now that the dabbling duck lineages more distantly related to mallard group (which includes the type species of "Anas") than the wigeons are should arguably be separated in their own genera. These would include the Baikal Teal, the Garganey, the spotted black-capped "Punanetta" group, and the shovelers and other blue-winged species. Whether the widgeons, which are very distinct in morphology [Livezey (1991)] and behavior [Johnson "et al." (2000)] , but much less so in mtDNA cytochrome "b" and NADH dehydrogenase subunit 2 sequences [Johnson & Sorenson (1999)] , should also be considered a distinct genus "Mareca" (including the Gadwall and Falcated Duck) is essentially the one remaining point of dispute as regards the question which taxa should remain in this genus and which ones should not.

pecies

The following arrangement is based on morphological [Livezey (1991)] , molecular [Johnson & Sorenson (1999), McCracken "et al." (2001)] and behavioral [Johnson "et al." (2000)] characters and presents apparent major evolutionary groupings compared to the subgenera the species were placed in at one time or another.

Probable genus "Sibirionetta" - Baikal Teal
*Baikal Teal, "Anas formosa" (formerly in "Nettion")

Probable genus "Querquedula" - Garganey (may include "Punanetta")
*Garganey, "Anas querquedula"

Probable genus "Punanetta"
*Silver Teal, "Anas versicolor"
*Puna Teal, "Anas puna" - formerly included in "Anas versicolor"
*Hottentot Teal, "Anas hottentota"

Probable genus "Spatula" - blue-winged ducks/shovelers and allies (polyphyletic?)
*Blue-winged Teal, "Anas discors"
*Cinnamon Teal, "Anas cyanoptera"
**Borrero's Cinnamon Teal, "Anas cyanoptera borreroi" - possibly extinct (late 20th century?)
*Red Shoveler, "Anas platalea"
*Cape Shoveler, "Anas smithii"
*Australasian Shoveler, "Anas rhynchotis"
*Northern Shoveler, "Anas clypeata"

Possible genus "Mareca" - wigeons (may include "Chaulelasmus" and "Eunetta")
*Eurasian Wigeon, "Anas penelope"
*Amsterdam Island Duck, "Anas marecula" - tentatively placed here; extinct (c.1800)
*American Wigeon, "Anas americana"
*Chiloe Wigeon, "Anas sibilatrix"

Subgenus "Chaulelasmus" - Gadwall
*Gadwall, "Anas strepera"
** Coues' Gadwall or Washington Island Gadwall, "Anas strepera couesi" - extinct (late 19th century)

Subgenus "Eunetta" - Falcated Duck
*Falcated Duck, "Anas falcata"

Subgenus "Dafila" - pintails
*Northern Pintail, "Anas acuta"
*Eaton's Pintail, "Anas eatoni"
**Kerguelen Islands Pintail, "Anas eatoni eatoni"
**Crozet Islands Pintail, "Anas eatoni drygalskii"
*Yellow-billed Pintail, "Anas georgica"
** South Georgia Pintail, "Anas georgica georgica"
** Niceforo's Pintail, "Anas georgica niceforoi" - extinct (1950s)
*White-cheeked Pintail, "Anas bahamensis" (formerly "Poecilonetta")
*Red-billed Teal, "Anas erythrorhyncha" (formerly "Poecilonetta")
*Cape Teal, "Anas capensis" (formerly in "Nettion")

Subgenus "Nettion" - teals (paraphyletic)
*Indian Ocean clade
**Bernier's Teal, "Anas bernieri"
**Mauritian Duck, "Anas theodori" - extinct (late 1690s)
**Sunda Teal, "Anas gibberifrons"
*** Rennell Island Teal, "Anas gibberifrons remissa" - extinct (c.1959)
**Grey Teal, "Anas gracilis" - formerly included in "Anas gibberifrons"
**Chestnut Teal, "Anas castanea"

*Atlantic/Red-and-green head clade
**Common Teal, "Anas crecca"
**Green-winged Teal, "Anas carolinensis" - formerly included in "Anas crecca"
**Speckled Teal, "Anas flavirostris"
***Andean Teal, "Anas (flavirostris) andinum"

*New Zealand clade (Placement unresolved)
**Auckland Islands Teal, "Anas aucklandica"
**Brown Teal, "Anas chlorotis" - formerly included in "Anas aucklandica"
**Macquarie Islands Teal, "Anas" cf. "chlorotis" - prehistoric
**Campbell Island Teal, "Anas nesiotis" - formerly included in "Anas aucklandica"

Subgenus "Melananas" - African Black Duck
*African Black Duck, "Anas sparsa"

Subgenus "Anas" - mallard and relatives (may include "Melananas")
*Basal African species ("Afranas")
**Meller's Duck, "Anas melleri"
**Yellow-billed Duck, "Anas undulata"

*American clade
**Mottled Duck, "Anas fulvigula" - sometimes included in "Anas platyrhynchos"
***Florida Duck, "Anas fulvigula fulvigula" - sometimes included in "Anas platyrhynchos"
**American Black Duck, "Anas rubripes" - sometimes included in "Anas platyrhynchos"
**Mexican Duck, "Anas diazi" - sometimes included in "Anas platyrhynchos"

* Pacific clade - the moa-nalos might be derived from this group.
**Mariana Mallard, "Anas (platyrhynchos) oustaleti" - sometimes considered a subspecies of "Anas superciliosa"; extinct (1981)
**Hawaiian Duck, "Anas wyvilliana" - sometimes included in "Anas platyrhynchos"
**Philippine Duck, "Anas luzonica"
**Laysan Duck, "Anas laysanensis" - sometimes included in "Anas platyrhynchos"
***Lisianski Duck, "Anas" cf. "laysanensis" - hypothetical; extinct (c.1845)
**Pacific Black Duck, "Anas superciliosa"

*Ambiguous
**Mallard, "Anas platyrhynchos"
**Spotbill, "Anas poecilorhyncha"
***Chinese Spotbill, "Anas (poecilorhyncha) zonorhyncha" - sometimes considered a subspecies of "Anas superciliosa"

Formerly placed in "Anas":
*Bronze-winged Duck, "Speculanas specularis"
*Crested Duck, "Lophonetta specularioides"
*Salvadori's Teal, "Salvadorina waigiuensis"

Fossil record

A number of fossil species of "Anas" have been described. Their relationships are often undetermined:
* "Anas" sp. (Late Miocene of China)
* "Anas" sp. (Late Miocene of Rudabánya, Hungary) [A mid-sized species: Bernor "et al." (2002)]
* "Anas greeni" (Ash Hollow Late Miocene?/Early Pliocene of South Dakota, USA) - "Nettion" red-and-green head clade (doubtful)?
* "Anas ogallalae" (Ogalalla Late Miocene?/Early Pliocene of Kansas, USA) - "Nettion" red-and-green head clade (doubtful)?
* "Anas pullulans" (Juntura Late Miocene?/Early Pliocene of Juntura, Malheur County, Oregon, USA) - "Punanetta"?
* "Anas cheuen" (Early-Middle Pleistocene of Argentina) - "Dafila"?
* "Anas bunkeri" (Early -? Middle Pliocene - Early Pleistocene of WC USA) - "Nettion" red-and-green head clade?
*Bermuda Islands Flightless Duck "Anas pachyscelus" (Shore Hills Late Pleistocene of Bermuda, W Atlantic)
* "Anas schneideri" (Late Pleistocene of Little Box Elder Cave, USA)

Several prehistoric waterfowl supposedly part of the "Anas" assemblage are nowadays not placed in this genus anymore, at least not with certainty:
* "Anas" basaltica" (Late Oligocene of "Warnsdorf", Czechia) is apparently an indeterminate heron.
* "Anas" blanchardi", "A." consobrina", "A." natator" are now in "Mionetta"
* "Anas" creccoides" (Early-mid Oligocene of Belgium), "A." risgoviensis" (Late Miocene of Bavaria, Germany) and "A." skalicensis" (Early Miocene of "Skalitz", Czechia), though possibly anseriform, cannot be placed with any certainty among modern birds at all.
* "Anas" albae" (Late Miocene of Polgárdi, Hungary), "A." eppelsheimensis" (Early Pliocene of Eppelsheim, Germany) , "A." isarensis" (Late Miocene of Aumeister, Germany) and "A." luederitzensis" (Kalahari Early Miocene of Lüderitzbucht, Namibia) are apparently Anatidae of unclear affiliations; the first might be a seaduck.
* "Anas" integra" and "A." oligocaena" are now in "Dendrochen"
* "Anas" robusta" is now tentatively placed in "Anserobranta"
* "Anas" velox" (Middle - Late? Miocene of C Europe) and "A." meyerii" (Middle Miocene of Öhningen, Germany; possibly the same species) do not seem to belong into the present genus either; they may still turn out to be ancestral dabbling ducks.

Highly problematic, albeit in a theoretical sense, is the placement of the moa-nalos. These are in all probability derived from a common ancestor of the Pacific Black Duck, the Laysan Duck, and the Mallard, and an unknown amount of other lineages. Phylogenetically, they may even form a clade within the traditional genus "Anas" [Sorenson (1999)] . However, as opposed to these species - which are well representative of dabbling ducks in general - the moa-nalos are the most radical departure from the anseriform bauplan known to science. This illustrates that in a truly evolutionary sense, a strictly phylogenetic taxonomy may be difficult to apply.

Footnotes

References

* Bernor, R.L.; Kordos, L. & Rook, L. (eds): Recent Advances on Multidisciplinary Research at Rudabánya, Late Miocene (MN9), Hungary: A compendium. "Paleontographica Italiana" 89: 3-36. [http://rocek.gli.cas.cz/Reprints/Bernor%20et%20al.pdf PDF fulltext]

* Carboneras, Carles (1992): Family Anatidae (Ducks, Geese and Swans). "In:" del Hoyo, Josep; Elliott, Andrew & Sargatal, Jordi (editors): "Handbook of Birds of the World, Volume 1: Ostrich to Ducks": 536-629. Lynx Edicions, Barcelona. ISBN 84-87334-10-5

* Johnson, Kevin P. & Sorenson, Michael D. (1999): Phylogeny and biogeography of dabbling ducks (genus Anas): a comparison of molecular and morphological evidence. "Auk" 116(3): 792–805. [http://elibrary.unm.edu/sora/Auk/v116n03/p0792-p0805.pdf PDF fulltext]

* Johnson, Kevin P. McKinney, Frank; Wilson, Robert & Sorenson, Michael D. (2000): The evolution of postcopulatory displays in dabbling ducks (Anatini): a phylogenetic perspective. "Animal Behaviour" 59(5): 953–963 [http://ducksrus.bu.edu/~msoren/pubs/AnimBehav2000b.pdf PDF fulltext]

* Kulikova, Irina V.; Drovetski, S. V.; Gibson, D. D.; Harrigan, R. J.; Rohwer, S.; Sorenson, Michael D.; Winker, K.; Zhuravlev, Yury N. & McCracken, Kevin G. (2005): Phylogeography of the Mallard ("Anas platyrhynchos"): Hybridization, dispersal, and lineage sorting contribute to complex geographic structure. "Auk" 122(3): 949-965. [English with Russian abstract] DOI: 10.1642/0004-8038(2005)122 [0949:POTMAP] 2.0.CO;2 [http://mercury.bio.uaf.edu/~kevin_mccracken/reprints/auk-122-949.pdf PDF fulltext] Erratum: "Auk" 122(4): 1309. DOI: 10.1642/0004-8038(2005)122 [0949:POTMAP] 2.0.CO;2

* Livezey, B. C. (1991): A phylogenetic analysis and classification of recent dabbling ducks (Tribe Anatini) based on comparative morphology. "Auk" 108(3): 471–507. [http://elibrary.unm.edu/sora/Auk/v108n03/p0471-p0507.pdf PDF fulltext]

* McCracken, Kevin G.; Johnson, William P. & Sheldon, Frederick H. (2001): Molecular population genetics, phylogeography, and conservation biology of the mottled duck ("Anas fulvigula"). "Conservation Genetics" 2(2): 87–102. DOI|10.1023/A:1011858312115 [http://mercury.bio.uaf.edu/~kevin_mccracken/reprints/cons-gen-2-87.pdf PDF fulltext]

* Sorenson "et al" (1999): Relationships of the extinct moa-nalos, flightless Hawaiian waterfowl, based on ancient DNA. "Proceedings of the Royal Society".