Generic boundaries of Leucochrysum and Waitzia (Asteraceae: Gnaphalieae)

Abstract

The Australasian clade of Gnaphalieae (Asteraceae) is an ecologically diverse group of species whose generic limits and phylogenetic relationships are still partly unresolved. Previous studies including hybridisation trials, morphological characterisation and preliminary phylogenetic analyses within the Gnaphalieae have suggested that two genera, namely, Waitzia and Leucochrysum, require further investigation into their generic boundaries. To explore the phylogenetic relationships of both genera, the present study used a combination of morphological and molecular approaches. The character traits of herbarium specimens from 14 species and six infraspecific taxa of Waitzia, Leucochrysum and Anemocarpa were examined. Chloroplast (psbA–trnH) and nuclear ribosomal ITS and ETS sequences were generated for phylogenetic analysis. Our findings support Waitzia in its current circumscription as a monophyletic group, whereas Leucochrysum was found to be polyphyletic. Leucochrysum fitzgibbonii was found to be the sister group of Waitzia and shares characters of the involucral bracts, indumentum and growth habit with that genus. The species is formally transferred to the genus Waitzia as W. fitzgibbonii.