Raukaua is a small genus of woody flowering plants in the family Araliaceae (order Apiales), with a distinctive austral distribution: its six species are native to southern Argentina and Chile, New Zealand, and the island of Tasmania. The genus sits within a broader Araliaceae clade that also includes the related genera Schefflera, Cheirodendron, Cephalaralia, and Motherwellia.
Plants in the genus vary considerably in growth habit. Raukaua laetevirens is a small tree found in the cool-temperate forests of southern Chile and Argentina, while Raukaua valdiviensis is a liana confined to the Valdivian temperate rain forest. All species have palmately compound leaves that display pronounced heteroblasty — the juvenile and adult leaf forms are conspicuously different in shape and texture. Raukaua simplex, one of three New Zealand members, is notable for producing root suckers on which leaf form grades from progressively more juvenile the further the sucker extends from the main shoot.
The type species, Raukaua edgerleyi, is indigenous to New Zealand. Māori traditionally extracted an aromatic oil from its leaves, and the essential oils of the New Zealand species have been the subject of phytochemical study.
Molecular phylogenetic work has confirmed that Raukaua as currently circumscribed is polyphyletic: the New Zealand species are sister to a clade of Melanesian–Polynesian Schefflera and Hawaiian Cheirodendron, while the South American species are allied with the Tasmanian Raukaua gunnii and the Australian genera Cephalaralia and Motherwellia. Because of this polyphyly, the South American and Tasmanian species are expected to be transferred to other genera in a future revision. Natural hybrids occur between the three New Zealand species.
Etymology
The genus name Raukaua is a Latinization of Raukawa, the Māori name for Raukaua edgerleyi, the type species. When Berthold Carl Seemann erected the genus in 1866 in the Journal of Botany, British and Foreign, he misspelled the name as Raukana; he published a correction in 1868 clarifying it should always be read as Raukaua.
Distribution
Raukaua has an austral distribution spanning three disjunct regions: southern Chile and Argentina (including the Valdivian temperate rain forest), New Zealand, and Tasmania. The three New Zealand species — R. anomalus, R. edgerleyi, and R. simplex — overlap enough to produce naturally occurring hybrids, while R. valdiviensis is restricted to the Valdivian temperate rain forest of South America.
History
The genus was erected by Berthold Carl Seemann in 1866 but was subsequently ignored by most authors, who placed its species in Pseudopanax or other genera. Raukaua was last formally revised in 1997 in the New Zealand Journal of Botany, with hybrid status clarified in 1998 and an Araliaceae nomenclator published in 2003. A 2012 molecular phylogenetic study confirmed the polyphyly of the genus, showing that the New Zealand species and the South American/Tasmanian species belong to separate evolutionary lineages within Araliaceae.
Taxonomy Notes
All Raukaua species have been placed in Pseudopanax at some point, and some in other genera. Molecular phylogenetics have shown the genus is polyphyletic: the New Zealand species are sister to Schefflera sensu strictissimo and Cheirodendron (Melanesian–Polynesian and Hawaiian lineages respectively), while the South American species ally with Raukaua gunnii (Tasmania), Cephalaralia, and Motherwellia (mainland Australia). A formal revision transferring the non-New Zealand species to appropriate genera is anticipated.
Cultural Uses
Māori traditionally extracted an aromatic oil from the leaves of Raukaua edgerleyi (raukawa). The essential oils of the New Zealand species have also been the subject of modern phytochemical analysis.
