Reassessment of a possible case of intraspecific gene flow across Australia's Great Dividing Range in the variegated fairy wren, Malurus lamberti (Aves: Maluridae), and its systematic consequences

Abstract

Two subspecies of the variegated fairy wren Malurus lamberti, Malurus lamberti lamberti and Malurus lamberti assimilis, are thought to exemplify a surprisingly rare case of intraspecific gene flow across eastern Australia’s Great Dividing Range. We screened 71 individuals within and beyond their putative hybrid zone for diversity in one mitochondrial and two anonymous nuclear loci, four microsatellite markers and diagnostically different plumage traits. Almost all supposed hybrid zone individuals were genotypically and phenotypically M. l. assimilis, but some carried mitochondrial DNA typical of M. l. lamberti. We infer an intermittently ‘leaky’ genetic boundary between the two taxa. Integrating this study with our earlier work on the M. lamberti group, we argue that speciation, albeit with some gene flow, between M. l. lamberti and all other taxa recently assigned to M. lamberti is essentially complete. A two-species taxonomy whereby one species, M. lamberti Vigors and Horsfield, 1827 (variegated fairy wren), comprises only what is currently called M. l. lamberti, and a second species, Malurus assimilis North, 1901 (purple-backed fairy wren), is for all other populations recently assigned to M. lamberti should be adopted and further tested.