Population genomics and phylogeography of four Australasian waterfowl

Biogeographic barriers can restrict gene flow, but variation in ecological
drivers of dispersal influences the effectiveness of these barriers among
different species. Detailed information about the genetic connectivity and
movement of waterfowl across biogeographic barriers in northern Australia
and Papua New Guinea is limited. We compared genetic connectivity for four
species of Australasian waterfowl that vary in their capacity and
predisposition for dispersal: Radjah Shelduck (Tadorna radjah), Wandering
Whistling-Duck (Dendrocygna arcuata), Green Pygmy-Goose (Nettapus
pulchellus), and Pacific Black Duck (Anas superciliosa). We obtained
>2,700 loci from double-digest restriction-associated DNA
sequencing for 15 to 40 individuals per species and found idiosyncratic
patterns of population structure among the four species. The mostly
sedentary Radjah Shelduck exhibited clear genetic differences between New
Guinea and Australia as well as among locations within Australia. In
contrast, the presumed sedentary Green Pygmy-Goose did not show obvious
structure. Likewise, populations of the more dispersive Wandering
Whistling Duck and Pacific Black Duck were unstructured and genetically
indistinguishable between southern New Guinea and northern Australia. Our
data suggest some Australo-Papuan biogeographical barriers are
insufficient to impede gene flow in waterfowl species capable of
dispersing great distances. In sedentary species like the Radjah Shelduck,
these barriers, perhaps coupled with its ecology and natural history,
restrict gene flow. Our findings bring new insight into the population
ecology of Australo-Papuan waterfowl.