New Names For the Kermadec Nikau Palm and Three Kings Cabbage Tree
The Kermadec nikau, hitherto known as Rhopalostylis cheesemanii Beccari or R. baueri var. cheesemanii (Beccari) Sykes, and long believed endemic to Raoul Island, has been relegated to synonymy with the Norfolk Island R. baueri (Seem.) H.Wendl. et Drude (de Lange et al. 2005). Rhopalostylis cheesemanii had been distinguished for the New Zealand R. sapida H.Wendl. et Drude and R. baueri, primarily by its globose fruits (those of R. baueri are ovoid) and larger size (which distinguished it from R. sapida but not R. baueri). Field work on both Raoul and Norfolk over the last twenty years has shown that there is significant overlap in fruit shape, and dimensions, thus, plants matching the description of R. baueri can be found on Raoul, and vice versa. Accordingly, as there are no other significant distinguishing characters, the authors refer the Raoul Island plants to the earlier named R. baueri. In addition to this name change, the typification of both palms is now finally resolved.From a conservation perspective, there is little change to the status of the Raoul Island palm (“At Risk/Range Restricted”), beyond that, it should now receive the qualifier “SO (Secure Overseas)”, as R. baueri is one of the few Norfolk Island indigenous plants to be secure on that island. On Raoul Island, though always abundant, the palm has following the successful eradication of rats four years ago, greatly expanded its range. On Norfolk, which is still infested with rodents, R. baueri is still regenerating, and at times locally abundant, but it cannot be doubted that it, and many other Norfolk plants and animals, would greatly benefit from rodent eradication, something that could achieved on that island if the local people wished.
The so called “Three Kings” Cabbage tree (Cordyline kaspar W.R.B.Oliv.) was described in 1956 by Reginald Oliver using a cultivated Three Kings Islands specimen, still growing at the former DSIR Research Station (now Hort Research) Mt, Albert, Auckland. Oliver was at pains to distinguish his new species from the New Zealand endemic C. australis (G.Forst.) Endl., because that was where past workers had placed the Three Kings plant. Oliver did not, however, critically compare C. kaspar with the Norfolk Island endemic C. obtecta (Graham) Baker. In their paper de Lange et al. (2005) note that Oliver may not have considered this until the following year, when he collected C. obtecta on Norfolk Island, and when, based on herbarium evidence he seemed to take an interest in their relationships. Unfortunately he died before his views (if any) could be made known. Subsequent field workers have shown that in New Zealand C. kaspar is not endemic to the Three Kings but that it also occurs locally at North Cape, at Murimotu Island and on the Poor Knights Islands, where it is locally common. On the taxonomic front several botanists have in the past advocated the need to critically compare C. kaspar with C. obtecta, so de Lange et al. (2005) have done this, and they report that they can find no significant differences, and so they refer C. kaspar to the earlier named C. obtecta. Again from a conservation perspective there is little change in the conservation status within the New Zealand part of this species range (“At Risk/Range Reestricted”), though the qualifier “TO (Threatened Overseas)” is now appropriate, as many C. obtecta populations are threatened outside the Norfolk Island National Park.
Reference
de Lange, P.J.; Gardner, R.O.; Crowcroft, G.M.; Stalker, F.; Cameron, E.K.; Braggins, J.E; Christian, M.L. 2005: Vascular flora of Norfolk Island: some additions and taxonomic notes. New Zealand Journal of Botany 43: 563-596.
Posted: 4 July 2005