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.[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
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 may have long played a major role in Anas evolution, with within-subgenus hybrids regularly and between-subgenus hybrids not infrequently being fully fertile.[1] The relationships between species are much obscured by this fact, and mtDNAsequence data is of dubious value in resolving their relationships;[2] 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 subgenusAnas, 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.
For these reasons, the dabbling duck lineages more distantly related to mallard group (which includes the type species of Anas) than the wigeons 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 wigeons, which are very distinct in morphology[3] and behavior,[4] but much less so in mtDNA cytochrome b and NADH dehydrogenasesubunit 2 sequences,[5] 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 current morphological,[3] molecular,[5][6] and behavioral[4] characters and presents apparent major evolutionary groupings compared to the subgenera the species were placed in at one time or another.
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 may be 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.[8] 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.[citation needed]
Bernor, R.L.; Kordos, L. & Rook, L. (eds): Recent Advances on Multidisciplinary Research at Rudabánya, Late Miocene (MN9), Hungary: A compendium. Paleontographica Italiana89: 3–36. 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. Auk116(3): 792–805. 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 Behaviour59(5): 953–963 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. Auk122(3): 949–965. [English with Russian abstract] DOI: 10.1642/0004-8038(2005)122[0949:POTMAP]2.0.CO;2 PDF fulltextErratum: Auk122(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. Auk108(3): 471–507. 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 Genetics2(2): 87–102. doi:10.1023/A:1011858312115PDF fulltext
Sorenson, et al. (1999): Relationships of the extinct moa-nalos, flightless Hawaiian waterfowl, based on ancient DNA. Proceedings of the Royal Society.
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