Anas

Anas is a genus of dabbling ducks. It includes the pintails, most teals, and the mallard and its close relatives. It formerly included additional species but following the publication of a molecular phylogenetic study in 2009 the genus was split into four separate genera. The genus now contains 31 living species. The name Anas is the Latin for "duck".

Systematics

The genus Anas was introduced by the Swedish naturalist Carl Linnaeus in 1758 in the tenth edition of his Systema Naturae. Anas is the Latin word for a duck. The genus formerly included additional species. In 2009 a large molecular phylogenetic study was published that compared mitochondrial DNA sequences from ducks, geese and swans in the family Anatidae. The results confirmed some of the conclusions of earlier smaller studies and indicated that the genus as then defined was non-monophyletic. Based on the results of this study, Anas was split into four proposed monophyletic genera with five species including the wigeons transferred to the resurrected genus Mareca, ten species including the shovelers and some teals transferred to the resurrected genus Spatula and the Baikal teal placed in the monotypic genus Sibirionetta.

Species

There are 31 extant species recognised in the genus:

Image	Common name	Scientific name	Distribution
	African black duck	Anas sparsa	eastern and southern sub-Saharan Africa from South Africa n north to South Sudan and Ethiopia with outlying populations in western equatorial Africa, in south east Nigeria, Cameroon and Gabon.
	Yellow-billed duck	Anas undulata	southern and eastern Africa.
	Meller's duck	Anas melleri	eastern Madagascar.
	Pacific black duck	Anas superciliosa	Indonesia, New Guinea, Australia, New Zealand, and many islands in the southwestern Pacific, reaching to the Caroline Islands in the north and French Polynesia in the east
	Laysan duck	Anas laysanensis	Hawaiian Islands
	Hawaiian duck	Anas wyvilliana	Hawaiian islands
	Philippine duck	Anas luzonica	the Philippines
	Indian spot-billed duck	Anas poecilorhyncha	Pakistan and India
	Eastern spot-billed duck	Anas zonorhyncha	Southeast Asia
	Mallard	Anas platyrhynchos	Alaska to Mexico, the Hawaiian Islands, across Eurasia, from Iceland and southern Greenland and parts of Morocco in the west, Scandinavia and Britain to the north, and to Siberia, Japan, and South Korea, in the east, south-eastern and south-western Australia and New Zealand
	Mottled duck	Anas fulvigula	Gulf of Mexico coast between Alabama and Tamaulipas and Florida
	American black duck	Anas rubripes	Saskatchewan to the Atlantic in Canada and the Great Lakes and the Adirondacks in the United States
	Mexican duck	Anas diazi	Mexico and the southern United States.
	Cape teal	Anas capensis	sub-Saharan Africa
	White-cheeked pintail	Anas bahamensis	Caribbean, South America, and the Galápagos Islands
	Red-billed teal	Anas erythrorhyncha	southern and eastern Africa
	Yellow-billed pintail	Anas georgica	South America, the Falkland Islands and South Georgia
	Eaton's pintail	Anas eatoni	island groups of Kerguelen and Crozet in the southern Indian Ocean
	Northern pintail	Anas acuta	Europe, Asia and North America
	Eurasian teal	Anas crecca	northern Eurasia
	Green-winged teal	Anas carolinensis	North America except on the Aleutian Islands
	Yellow-billed teal	Anas flavirostris	Argentina, the Falkland Islands, Chile, Peru, Bolivia, Uruguay, and Brazil.
	Andean teal	Anas andium	Andean highlands of Colombia, Venezuela, and Ecuador
	Sunda teal	Anas gibberifrons	Indonesia.
	Andaman teal	Anas albogularis	Andaman Islands and Great Coco Island
	Grey teal	Anas gracilis	Australia and New Zealand
	Chestnut teal	Anas castanea	Tasmania and southern Victoria, New Guinea and Lord Howe Island
	Bernier's teal	Anas bernieri	Madagascar
	Brown teal	Anas chlorotis	New Zealand
	Auckland teal	Anas aucklandica	Auckland Islands south of New Zealand
	Campbell teal	Anas nesiotis	New Zealand

Extinct Species

Mariana mallard, Anas oustaleti
Mascarene teal, Anas theodori
Chatham Island Duck, Anas chathamica

Formerly placed in Anas:

Bronze-winged duck, Speculanas specularis
Crested duck, Lophonetta specularioides
Baikal teal Sibirionetta formosa
Salvadori's teal, Salvadorina waigiuensis
species in the genus Mareca, the wigeons
species in the genus Spatula, the shovelers and related teals

Phylogeny

Cladogram based on the analysis of Gonzalez and colleagues published in 2009.

Fossil record

A number of fossil species of Anas have been described. Their relationships are often undetermined:

†Anas sp.
†Anas sp.
†Anas amotape
†Anas bunkeri – Nettion red-and-green head clade?
†Anas cheuen Agnolín 2006 – Dafila?
†Anas ganii Burchak-Abramovich, Suspanov and David 1996
†Anas greeni – Nettion red-and-green head clade ?
†Anas itchtucknee McCoy 1963 doubtful validity
†Anas kisatibiensis Burchak-Abramovich and Mczedlidze 1995
†Anas kurochkini Zelenkov & Panteleyev 2015
†Anas lambrechti Spillman 1942
†Anas ogallalae – Nettion red-and-green head clade ?
Bermuda Islands flightless duck †Anas pachyscelus Wetmore 1960
†Anas pullulans – Punanetta?
†Anas schneideri Emslie 1985

Several prehistoric waterfowl supposedly part of the Anas assemblage are nowadays not placed in this genus anymore, at least not with certainty:

†"Anas" basaltica is apparently an indeterminate heron.
†"Anas" blanchardi, "A." consobrina, "A." natator are now in Mionetta
†"Anas" creccoides, "A." risgoviensis and "A." skalicensis, though possibly anseriform, cannot be placed with any certainty among modern birds at all.
†"Anas" albae, "A." eppelsheimensis and "A." isarensis are apparently Anatidae of unclear affiliations
†"Anas" integra and "A." oligocaena are now in Dendrochen.
†"Anas" lignitifila from the Late Miocene of Tuscany has been moved to its own genus, Bambolinetta, being a highly unusual marine waterfowl.
†"Anas" luederitzensis may belong within Oxyurini
†"Anas" robusta is now tentatively placed in Anserobranta.
†"Anas" sansaniensis is now placed in Chenoanas
†"Anas" velox and "A." meyerii do not seem to belong Anas, and they may be ancestral dabbling ducks.

Anas elapsum is now synonymised with the extant Hardhead. Anas gracilipes and Anas strenuum are both junior synonyms of the extant Chestnut teal.
Highly problematic, albeit in a theoretical sense, is the placement of the moa-nalos. These may be descended from a common ancestor of dabbling ducks such as the Pacific black duck, Laysan duck, and mallard. Phylogenetically, they may even form a clade within the traditional genus Anas. However, when compared to these species – which are representative of dabbling ducks in general – the moa-nalos are a radical departure from the Anseriforme bauplan. This illustrates that in a truly evolutionary sense, a strictly phylogenetic taxonomy may be difficult to apply.