Genetic and morphological relationships of fieldwrens (Calamanthus): implications for conservation status and management

Sound taxonomy is important for providing a scientific basis for the listing of threatened taxa and allowing informed decisions for conservation management. The Australian fieldwrens (Acanthizidae: Calamanthus spp.), small passerines of shrublands across mesic to arid southern Australia, have been challenging in this respect. Difficulties in interpreting the variation in morphology and colouration across their geographic range have resulted in taxonomic controversy for a century; multiple arrangements of species and subspecies have been proposed, including a prevailing view that there are two species and seven subspecies in the Rufous Fieldwren, Calamanthus campestris complex. Two island subspecies (C. campestris hartogi and C. c. dorrie) are currently listed as Vulnerable. We hypothesised that C. campestris is monotypic (including C. montanellus) and that variation is clinal across mainland populations. Results of our genetic, morphological and colour pattern analyses are largely consistent with this hypothesis. However, we did find evidence of genetic divergence between eastern and western populations and some genetic support for recognition of C. c. hartogi (Dirk Hartog Island) based on divergence in nuclear allele frequencies. Together, our results provide a strong case for the hypotheses that C. montanellus is a synonym of C. campestris, and that rather than consisting of seven subspecies, C. campestris comprises two mainland subspecies C. c. campestris and C. c. rubiginosus east and west, respectively, of 133 degrees longitude, and only one island subspecies, C. c. hartogi. In this regard, the currently recognised C. c. dorrie is nominated for removal from threatened species lists.