The noble and the exalted: a multidisciplinary approach to resolving a taxonomic controversy within Ptilotus (Amaranthaceae)

Abstract

A molecular study on Ptilotus nobilis (Lindl.) F.Muell. var. nobilis and P. exaltatus Nees var. exaltatus led to the conclusion that these taxa are conspecific, resulting in the synonymisation of the latter under the former as P. nobilis subsp. nobilis. In this study, we test previous taxonomic concepts in the P. nobilis–P. exaltatus species group by examining (1) the morphology of specimens in the herbarium and field, and (2) ecological and geographic partitioning of two widespread and broadly sympatric taxa in the group, using Maxent and CART models. We provide strong evidence supporting the reinstatement of P. exaltatus as distinct from P. nobilis, on the basis of multiple morphological characters and strong ecological and geographic partitioning, the latter showing how large-scale ecological data can be used to help resolve taxonomic issues. In addition, we raise P. nobilis subsp. angustifolius (Benl) Lally & W.R.Barker to the rank of species as P. angustifolius (Benl) T.Hammer and reinstate P. semilanatus (Lindl.) F.Muell. ex J.M.Black.