A taxonomic re-evaluation of Hibiscus trionum (Malvaceae) in Australasia

Hibiscus trionum has generally been regarded as naturalised in Australia and New Zealand. Two varieties are sometimes accepted as occurring in Australia: H. trionum var. trionum and H. trionum var. vesicarius, with the latter occasionally treated as indigenous. Following studies of the variation within H. trionum in Australia and New Zealand we propose that there are three indigenous species in this complex. Of the three species, one, Hibiscus richardsonii, occurs in coastal regions of New South Wales, Australia and the northeastern half of the North Island, New Zealand, Hibiscus tridactylites Lindley occurs in inland southern and eastern Australia, and Hibiscus verdcourtii, described herein, occurs widely in inland Australia, especially north of latitude 28 degrees S. In addition, we provide a description and informally recognise a diploid race of H. trionum s.l. that is widespread in New Zealand. In past treatments of the species in New Zealand this diploid race has either been treated as indigenous or included with H. richardsonii under the name oH. trionumo as naturalised. A key is provided to identify these taxa.