Chatham Islands, New Zealand

The Chatham Ribbonwood has been known to scientists as either Plagianthus chathamicus or P. betulinus var. chathamicus - names that were coined by Leonard Cockayne following his study of Chatham Island plants during his visit to the islands in 1901. Cockayne distinguished the Ribbonwood from the New Zealand tree because it lacked the distinctive juvenile divaricating growth habit of that species. Initially Cockayne felt the tree merited species rank, publishing it in 1902 as P. chathamicus but later in 1912 he revised his opinion and treated the Chatham island Ribbonwood as a variety of the New Zealand tree (P. betulinus var. chathamicus).

One problem out of Cockayne's control was determining the correct name for the New Zealand Ribbonwood. This tree was long known to New Zealanders as P. betulinus - a name coined by the botanist Allan Cunningham in 1840 based on specimens his brother Richard had gathered from the Kawakawa River, Bay of Islands North Island, in 1834. However, the same tree already had a name, albeit in another genus Philippodendrum, as P. regium, having been formally described in 1837 from a tree growing in a garden in Paris by the French botanist Pierre Poiteau. According to the botanical rules of nomenclature, Poiteau's name, as the older name had priority over Cunningham's, and so the New Zealand tree became known as Plagianthus regius.

This was all very nice - as far as botanical rules of nomenclature go - but it left the Chatham Ribbonwood in a state of limbo. Why? Well it already had two valid names, at two different ranks, one at species rank (P. chathamicus) and one at variety rank (P. betulinus var. chathamicus). As Cockayne himself admitted in his 1912 paper, claim to species rank was weak because the only real difference was that the Chatham tree lacked a divaricating juvenile growth habit. However, with the recognition that P. regius was the correct name for the New Zealand tree to continue to refer to the Chatham tree as P. betulinus var. chathamicus was confusing, because people would be left wondering what ever happened to P. betulinus var. betulinus? So to avoid potentially confusing people further, the Chatham Ribbonwood has been referred to as P. chathamicus by most publications dealing with the islands flora throughout most of the last two decades. This decision was however, admittedly unsatisfactory. After all, as Leonard Cockayne had already observed Chatham Ribbonwood's are not that different from New Zealand ones.

Therefore in the latest New Zealand Journal of Botany, de Lange (2008) has resolved the issue by publishing a new name for the Chatham Ribbonwood within P. regius at the more appropriate rank of subspecies (P. regius subsp. chathamicus), so tidying up 106 years of botanical inconsistency and confusion.

Reference: de Lange, P.J. 2008: Plagianthus regius subsp. chathamicus (Malvaceae) - a new combination for a Chatham Islands endemic tree. New Zealand Journal of Botany 46: 381-386.