Phylogeography of the blue-winged kookaburra Dacelo leachii across tropical northern Australia and New Guinea

Phylogeographic studies of northern Australian birds frequently detect the influence of the Carpentarian Barrier in vicariantly structuring present-day genetic variation. Several barriers further west (e.g. Canning Barrier), and, where data are available, the Arafura Sea and Torres Strait separating Australia and New Guinea have an overall lesser effect. Using sequence data from mitochondrial (mtDNA) and nuclear DNA, we tested whether the Blue-winged Kookaburra (Dacelo leachii), widespread in monsoonal northern Australia and southern New Guinea, shows evidence of vicariance by these barriers. Viewed in phylogenetic context of other Australo-Papuan kookaburras (D. novaeguineae, D. gaudichaud, D. tyro), clear phylogeographic subdivisions were absent within the range of D. leachii. Subspecies groupings explained a significant amount of molecular variance within D. leachii, the most distinct being New Guinean D. l. intermedia. Genealogical relationships among mtDNA haplotypes suggest a recent connection between New Guinea and Western Australia, a history recently proposed for at least one other bird species of similar open woodland habitat. Species distribution modelling similarly indicated that climatic conditions during the last glacial maximum (LGM) may have facilitated a connection between New Guinea and present-day Western Australia along the exposed Arafura shelf, and that suitable conditions remained continuous across the Carpentarian Barrier during the LGM. This work adds to a growing body of data on population genetic structuring of Australia?s birds in relation to biogeographic barriers and it is the first such analysis of a large-bodied, non-passerine bird having an extensive geographic range in tropical and subtropical Australia and New Guinea.