font settings

Font Size: Large | Normal | Small
Font Face: Verdana | Geneva | Georgia

Anas

(Genus)

Overview

[ Back to top ]

Anas is a 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[1]. 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.

Systematics

[ Back to top ]

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 longplayed a major role in Anas evolution, with within-subgenus hybrids regularly and between-subgenus hybrids not infrequently being fully fertile[2]. The relationships between species are much obscured by this fact, and mtDNA sequence data is of dubious value in resolving their relationships[3]; 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 lineagesmore 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[4] and behavior[5], but much less so in mtDNA cytochrome b and NADH dehydrogenase subunit 2 sequences[6], 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.

Species

The following arrangement is based on morphological[7], molecular[8] and behavioral[9] characters and presents apparent major evolutionary groupings compared to the subgenera the species were placed in at one time or another.

The puzzling Baikal Teal (Anas formosa, male)

Probable genus Sibirionetta - Baikal Teal

Probable genus Querquedula - Garganey (may include Punanetta)

Probable genus Punanetta

Red Shoveler, Anas platalea

Probable genus Spatula - blue-winged ducks/shovelers and allies (polyphyletic?)

Male American Wigeon, Anas americana

Possible genus Mareca - wigeons (may include Chaulelasmus and Eunetta)

Subgenus Chaulelasmus - Gadwall

Subgenus Eunetta - Falcated Duck

Subgenus Dafila - pintails

Subgenus Nettion - teals (paraphyletic)

Green-winged Teal, Anas carolinensis

Subgenus Melananas - African Black Duck

Yellow-billed Duck, Anas undulata

Subgenus Anas - mallard and relatives (may include Melananas)

The last male Mariana Mallard, c.1980

Formerly placed in Anas:

Fossil Record

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

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

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[11]. 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.

Photos

[ Back to top ]

Taxonomy

[ Back to top ]

The Genus Anas is further organized into finer groupings including:

References

[ Back to top ]

Footnotes

[ Back to top ]
  1. ^ Carboneras (1992)
  2. ^ Carboneras (1992); see also Mariana Mallard.
  3. ^ e.g. Kulikova et al. (2005)
  4. ^ Livezey (1991)
  5. ^ Johnson et al. (2000)
  6. ^ Johnson & Sorenson (1999)
  7. ^ Livezey (1991)
  8. ^ Johnson & Sorenson (1999), McCracken et al. (2001)
  9. ^ Johnson et al. (2000)
  10. ^ A mid-sized species: Bernor et al. (2002)
  11. ^ Sorenson (1999)

Sources

[ Back to top ]
Last Revised: November 20, 2008