Implications of mitochondrial DNA polyphyly in two ecologically undifferentiated but morphologically distinct migratory birds, the masked and white-browed woodswallows Artamus spp. of inland Australia


  • Leo Joseph,

  • Thomas Wilke,

  • José Ten Have,

  • R. Terry Chesser

L. Joseph (correspondence), Department of Ornithology, Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, Philadelphia PA, 19103-1195 USA. T. Wilke, Animal Ecology and Systematics, Justus Liebig University Giessen, Heinrich-Buff-Ring 26-32 (IFZ), D-35392 Giessen, Germany, J. Ten Have, CSIRO Entomology, GPO Box 1700, Canberra City, Australian Capital Territory 2601, Australia. R. Terry Chesser, USGS/PWRC, Smithsonian Institution, National Museum of Natural History, Division of Birds MRC-116, P.O. Box 37012, Washington, DC 20013-7012 USA. Present address of L. Joseph: Australian National Wildlife Collection, CSIRO Sustainable Ecosystems, GPO Box 284, Canberra City, Australian Capital Territory 2601, Australia. Email:


The white-browed woodswallow Artamus superciliosus and masked woodswallow A. personatus (Passeriformes: Artamidae) are members of Australia's diverse arid- and semi-arid zone avifauna. Widely sympatric and among Australia's relatively few obligate long-distance temperate-tropical migrants, the two are well differentiated morphologically but not ecologically and vocally. They are pair breeders unlike other Artamus species, which are at least facultative cooperative breeders. For these reasons they are an excellent case in which to use molecular data in integrative study of their evolution from ecological and biogeographical perspectives. We used mitochondrial DNA (mtDNA) to test whether they are each other's closest relatives, whether they evolved migration independently, whether they have molecular signatures of population expansions like some other Australian arid zone birds, and to estimate the timing of any inferred population expansions. Their mtDNAs are monophyletic with respect to other species of Artamus but polyphyletic with respect to each other. The two species appear not to have evolved migration independently of each other but their morphological and mtDNA evolution have been strongly decoupled. Some level of hybridization and introgression cannot be dismissed outright as being involved in their mtDNA polyphyly but incomplete sorting of their most recent common ancestor's mtDNA is a simpler explanation consistent with their ecology. Bayesian phylogenetic inference and analyses of diversity within the two species (n=77) with conventional diversity statistics, statistical parsimony, and tests for population expansion vs stability (Tajima's D, Fu's Fs and Ramos-Onsin and Rozas's R2) all favour recent population increases. However, a non-starlike network suggests expansion(s) relatively early in the Pleistocene. Repeated population bottlenecks corresponding with multiple peaks of Pleistocene aridity could explain our findings, which add a new dimension to accruing data on the effects of Pleistocene aridity on the Australian biota.