| 翻訳と辞書 |
Anas
''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. However, there are 42 species verified by ITIS,〔 and the IUCN recognizes 46 species.〔
==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.〔 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.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
■ウィキペディアで「Anas」の詳細全文を読む
スポンサード リンク
| 翻訳と辞書 : 翻訳のためのインターネットリソース |
Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.
|
|