Anas falcata

The falcated duck or falcated teal (Mareca falcata) is a gadwall-sized dabbling duck from Asia. The closest relative of this species is the gadwall, followed by the wigeons. The species was assigned to the proposed genus Mareca after its previous placement in the genus Anas was found to be paraphyletic in 2009. There are many species that have mitochondrial DNA lineages that are phylogenetically intermixed with other species, but studies have rarely tested the cause of such paraphyly. In a study that was conducted, there were tested two hypotheses that could explain mitochondrial paraphyly of Holarctic gadwalls (Anas strepera) with respect to Asian falcated ducks (A. falcata). First, hybridization could have resulted in falcated duck mitochondrial DNA (mtDNA) introgressing into the gadwall gene pool. Second, gadwalls and falcated ducks could have diverged so recently that mtDNA lineages have not sorted to reciprocal monophyly. They used coalescent analyses of three independent loci to distinguish between these two hypotheses. Two lines of evidence support introgression. First, analyses of the three loci combined show that some introgression is necessary to explain current genetic diversity in gadwalls. Second, they generated alternative predictions regarding time since divergence estimated from mtDNA: falcated ducks and gadwalls would have diverged between 65,000 and 700,000 years before present (ybp) under the introgression hypothesis and between 11,000 and 76,000 ybp under the incomplete lineage sorting hypothesis. The two independent nuclear introns indicated that these species diverged between 210,000 and 5,200,000 ybp, which did not overlap the predicted time for incomplete lineage sorting. These analyses also suggested that ancient introgression (similar to 14,000 ybp) has resulted in the widespread distribution and high frequency of falcated-like mtDNA (5.5% of haplotypes) in North America. This is the first study to use a rigorous quantitative framework to reject incomplete lineage sorting as the cause of mitochondrial paraphyly. The falcated duck breeds in eastern Asia. It nests in eastern Russia, in Khabarovsk, Primorskiy, Amur, Chita, Buryatia, Irkutsk, Tuva, eastern Krasnoyarsk, south central Sakha Sakhalin, extreme northeastern North Korea and northern China, in northeastern Inner Mongolia, and northern Heilongjiang, and in northern Japan, Hokkaidō, Aomori, and the Kuril Islands. It is widely recorded well outside its normal range, but the popularity of this beautiful duck in captivity clouds the origins of these extralimital birds. This dabbling duck is strongly migratory and winters in much of Southeast Asia. In India: Uttar Pradesh, Bihār, Assam, eastern Haryāna. Also in northern Bangladesh, northern and central Myanmar, northern Laos to the Mekong River, northern Vietnam (from about Hanoi north), and China: Hainan, Taiwan, Yunnan, Guangxi, Guangdong, Fujian, Jiangxi, northern Hunan, Hubei, Zhejiang, Anhui, Jiangsu, Shandong, southern Hebei, Shanxi, northern Shaanxi. It is gregarious outside the breeding season and will then form large flocks. It is estimated that there are about 89,000 falcated ducks in total; this is much higher than the previous population estimate of 35,000 worldwide. During a survey done in Central China, a migratory area in the winter for the falcated duck, the numbers of animals sighted was minimal. In 2004 only 4 were recorded, and in 2005 only 10.