Biogeographic models of gene flow in two waterfowl of the australo-papuan tropics

There are many large, easy-to-observe anseriform birds (ducks, geese, and swans) in northern Australia and New Guinea and they often gather in large numbers. Yet, the structure of their populations and their regional movements are poorly understood. Lack of understanding of population structure limits our capacity to understand source-sink dynamics relevant to their conservation or assess risks associated with avian-borne pathogens, in particular, avian inu-enza for which waterfowl are the main reservoir species. We set out to assess present-day genetic connectivity between populations of two widely distributed waterfowl in the Australo-Papuan tropics, magpie goose Anseranas semipalmata (Latham, 1798) and wandering whistling-duck Dendrocygna arcuata (Horseld, 1824). Microsatellite data were obtained from 237 magpie geese and 64 wander-ing whistling-duck. Samples were collected across northern Australia, and at one site each in New Guinea and Timor Leste. In the wandering whistling-duck, genetic diversity was signicantly apportioned by region and sampling location. For this species, the best model of population structure was New Gui-nea as the source population for all other populations. One remarkable result for this species was genetic separation of two ocks sampled contemporane-ously on Cape York Peninsula only a few kilometers apart. In contrast, evidence for population structure was much weaker in the magpie goose, and Cape York as the source population provided the best t to the observed structure. The ne scale genetic structure observed in wandering whistling-duck and magpie goose is consistent with earlier suggestions that the west-coast of Cape York Peninsula is a yway for Australo-Papuan anseriforms between Australia and New Guinea across Torres Strait.