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. 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. 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. The relationships between species are much obscured by this fact, and mtDNA sequence data is of dubious value in resolving their relationships; 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. 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 and behavior, but much less so in mtDNA cytochrome b and NADH dehydrogenase subunit 2 sequences, 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.
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|size min.:||63||cm||size max.:||68||cm|
|incubation min.:||28||days||incubation max.:||29||days|
|fledging min.:||60||days||fledging max.:||65||days|
Video Mellers Duck
copyright: Josep del Hoyo
A. melleri is among the largest species of wildfowl found in Madagascar and is widely hunted and trapped for subsistence (and for sport). Interviews with hunters at Lake Alaotra suggest c.450 individuals are taken each year, constituting 18% of the global population. Long term deforestation of the central plateau, conversion of marshes to rice-paddies and degradation of water quality in rivers and streams, as a result of deforestation and soil erosion, have probably contributed to its decline. Widespread exotic carnivorous fishes, notably Micropterus salmoides and Channa spp., may threaten young and cause desertion of otherwise suitable habitat. Its decline on Mauritius has been attributed to hunting, pollution and introduced rats and mongooses as well as possible displacement by introduced Common Mallard Anas platyrhynchos. Pairs are very territorial and susceptible to human disturbance.