International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.2, 74-82 http://ecoevopublisher.com/index.php/ijmec 77 genetic data indicate that domestic ducks also originated matrilineally through genetics within Eurasian mallards and were migrating and pouring into island nations like the Andaman and Nicobar Islands from southern India and Southeast Asia (De et al., 2021). The presence of rare genetic clusters in these countries implies more than a single process of domestication and dispersal. 3.3 Molecular clock estimates of domestication and divergence time windows Estimates of molecular clocks based on whole-genome resequencing and ddRAD-seq data locate the split of mallard-like ducks from their closest relatives around 1~2 million years ago, followed by Holocene and Pleistocene radiations and divergences in populations (Jiang et al., 2021; Kaminski et al., 2024). Demographic analysis has shown that house ducks have undergone population bottlenecks since the last glacial maximum, and differentiation between large geographic populations is pre-human mediated domestication, suggesting complex demographic history subject to natural as well as anthropogenic pressures (Jiang et al., 2021). Figure 2 Images of 26 individual duck populations (Adopted from Zhang et al., 2023) 3.4 Environmental changes as drivers of duck migration and population formation Environmental disturbances, for instance, glacials and climatic cycles, have been worldwide forces in causing duck migration, population bottlenecks, and novel population formation. The final glacial maximum, for instance, caused severe bottlenecks within Chinese domestic ducks, whereas postglacial periods facilitated stepwise colonization and secondary contact among lineages (Jiang et al., 2021; Scribner et al., 2024). Natural adaptation and adaptation of native environments, like that in the Andaman local duck case, have also influenced the genetic composition of duck populations and climate-change tolerance (De et al., 2021). 4 Distribution Patterns and Dispersal Pathways of Duck Populations in Different Climate Zones 4.1 Distribution characteristics and population connectivity of ducks in tropical, temperate, and frigid zones Duck populations in varying climatic zones show intense variation in distribution and connectivity. Spot-billed Ducks and Mallards overwhelm the most species-rich species in temperate coastal wetlands in eastern China, with the greatest diversity and abundance on tidal flats (Han, 2024). Abundance and duck community structure vary significantly among habitats as a response to adaptation against environmental elements and resources in local habitats (Luo et al., 2024). In frigid habitats, i.e., Arctic and subarctic, long-tailed ducks breed in the northern breeding sites and move to temperate marine habitats for wintering, indicating high migratory connectivity between breeding and wintering sites (Karwinkel et al., 2020). These patterns indicate the ecological flexibility and broad climatic tolerance of duck species.
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