A taxonomic framework for interpreting evolution within the Amytornis textilis—modestus complex of grasswrens

Abstract

Recent evidence points to the Amytornis textilis—modestus complex of grasswrens being not one but two species: Amytornis textilis (Western Grasswren), including A. t. myall, and Amytornis modestus (Thick-billed Grasswren). We present morphological support for this change and evidence of diversity within both A. t. textilis and A. modestus. In the latter we reinstate the currently unrecognised subspecies A. m. modestus from the valleys of the MacDonnell Ranges, which is presumed extinct, and A. m. indulkanna, ranging north-west of Lake Eyre and Lake Torrens. Other discrete populations are described at the periphery of the northern Flinders Ranges and in the south-western Lake Frome Basin. The former resembles A. m. indulkanna but shows sexual dimorphism in the tail. The population from the south-west Lake Frome Basin shares sexual dimorphism in the tail with the Flinders Ranges population but has a longer tail, and it is more strongly marked, darker and less consistently ‘thick-billed’ than any of the other three. Populations north-east of Lake Eyre and in New South Wales are incompletely evaluated. Molecular genetic studies are planned to clarify relationships between all extant and extinct populations of the complex.