Plumage patterns are good indicators of taxonomic diversity, but not of phylogenetic affinities, in Australian grasswrens Amytornis (Aves: Maluridae)

Abstract

The grasswrens (Maluridae: Amytornis) are elusive songbirds from the arid zones of Australia. Although some other Australian bird genera are also largely restricted to arid regions, none show the level of localized taxonomic diversity seen in Amytornis. Furthermore, their cryptic plumage patterns provide excellent camouflage but make it difficult to determine whether shared patterns reflect phylogenetic relationships or adaptations to similar terrain. To resolve the systematics and patterns of ecological diversification within Amytornis, we here present the results of a phylogenetic analysis of mitochondrial and nuclear multi-locus data for all recognized species and most subspecies, using traditional concatenation-based methods as well as a coalescent-based species-tree approach. Phylogenetic patterns retrieved by the species-tree approach were highly congruent with traditional methods, although branch support was generally higher in concatenation-based analysis, suggesting that species-tree methods may furnish more conservative results. In terms of identifying taxonomic diversity there was good concordance between plumage-based assessments and DNA distances. The same concordance was not found when comparing plumage-based and DNA-based predictions of phylogenetic relationships. Four primary lineages were identified: (a) barbatus; (b) merrotsyi; (c) the textilis complex, purnelli, ballarae, goyderi and housei; and (d) woodwardi, dorotheae, and the striatus complex. There was no robust resolution of relationships between lineages. It appears that in Amytornis, plumage differentiation between discrete populations is taxonomically significant, and not greatly influenced by ecophenotypic variation. However, at the deeper phylogenetic level, similar suites of plumage characters may be phylogenetically uninformative because of homoplasy. The study reveals higher levels of taxonomic diversity in Amytornis than previously recognized, with many taxa being highly localized. Such extensive short range endemism is mainly encountered in poorly-dispersing invertebrates and is unique in Australian birds. The identification here of the additional restricted range taxa has important conservation implications.