Abstract
Taxon differentiation in Urtica from Australia and New Zealand initially appears to be uncomplicated, with taxa being easy to distinguish. However, a revision of the type material, more recent collections and a comparison of Australian and New Zealand material shows that three of the names are misapplied. Urtica gracilis (as U. dioica subsp. gracilis, North America) has been reported as introduced to New Zealand, but molecular data retrieve the corresponding specimens with the other NZ-species and we argue that they belong to the polygamous Australian species Urtica incisa. A critical revision of the protologues and type collections reveals that the names Urtica incisa, originally described from mainland Australia, and U. incisa var. linearifolia from Tasmania, have been misapplied to New Zealand taxa. Both New Zealand “Urtica linearifolia” and “U. incisa” represent unnamed taxa and are here formally described as Urtica perconfusa and Urtica sykesii, respectively. Urtica perconfusa corresponds to what is erroneously known as U. linearifolia. Urtica sykesii is an overlooked species, erroneously interpreted as U. incisa in New Zealand. It may be differentiated from U. incisa Poir. by its smaller, deltoid leaf lamina with a truncate to subcordate base (versus truncate to cuneate), fewer leaf teeth (9–12 on each side rather than 14–20 in U. incisa) and smaller plant size (20–60 cm rather than 60–200 cm in U. incisa). We found evidence for the presence of true introduced U. dioica subsp. dioica in New Zealand, but not for U. gracilis. Rather, New Zealand specimens assigned to the putatively introduced northern hemisphere U. gracilis belong to U. incisa as described from Australia. Typifications for the species treated here are provided, including an updated key to the Australian and New Zealand taxa. There are thus six native species of Urtica in New Zealand, four of them endemic, and two also indigenous in Australia.