Morphological and molecular evidence of population divergence in a widespread shorebird across its southern mainland Australian distribution.

We characterize geographical variation in the genetics, ecology, morphology and plumage of the Hooded Plover Charadrius cucullatus, a threatened shorebird widespread on coasts (south-east) and saltlakes (south-west) across the southern mainland of Australia. We confirm the distinctness of populations on either side of the Nullabor Plain/Great Australian Bight indicating that this apparent biogeographic barrier to terrestrial flora and fauna also influenced the phylogeographic pattern of a resident shorebird which is dependent on access to saline/hypersaline water. Western birds are genetically distinct, larger and have darker plumage than those in the east. Distinct ecological differences also exist, with eastern birds being resident, usually occurring on ocean beaches, with generalised diets and seasonal, solitary breeding. Western birds are nomadic, breeding when suitable conditions prevail, and exhibit more specialized diets, and may at times breed semi-colonially. Within the extensive eastern population, genetic analyses revealed an isolation by distance pattern, as well as genetic evidence of a long distance dispersal event. South Australian birds are distinct from Victorian birds, but cluster closely with Victorian birds in all genetic analyses. The western population features little genetic structuring, consistent with nomadism and congregatory behavior associated with drought/flood events. The distinctness of western populations found using multiple lines of evidence and the lack of evidence for any recent migration events across the Nullabor Plain, suggests that previously described subspecies warrant reinstatement, and that these evolutionary units require conservation assessment, as has been recognized by national conservation authorities. Conservation management of the eastern population should occur across its distribution, taking care to capture the genetic variability which is evident within this population. Further exploration of genetic variation between Eastern states is suggested. [ABSTRACT FROM AUTHOR]