Phylogeography and taxonomy of the Little Bronze-Cuckoo (Chalcites minutillus) in Australia's monsoon tropics

We investigated relationships and phylogeographical structure among Australian populations of the obligatorily brood-parasitic Little Bronze-cuckoo (Chalcites minutillus) based on analyses of microsatellite and mtDNA sequences. We find that these populations are paraphyletic with respect to each other and suggest that this is a result of a combination of incomplete lineage sorting and gene flow. Our results show that the Australian populations of the C. minutillus complex are at a time in their evolution where their differentiation is incomplete and may even have been largely, and recently, arrested. Gene flow is particularly indicated between Top End-Kimberley and Cape York Peninsula populations. We examine how these findings might inform the notoriously controversial taxonomic debate about these populations. We question the merit of recognising the taxon russatus but acknowledge that analyses of New Guinean populations are needed. C. m. barnardi, which breeds in central eastern Australia, was the most differentiated in molecular markers. Further work is needed to test whether populations recognised as C. m. russatus and C. m. minutillus beyond Australia are indeed closest relatives to their respective Australian counterparts. The relationship between host specificity and patterns of genetic diversity should also be explored.