A taxonomic appraisal of the Chatham Islands flax (Phormium tenax) using morphological and DNA fingerprint data

Abstract

A range of leaf forms of Phormium tenax J.R.Forst. & G.Forst. can be observed in the wild on the Chatham Island archipelago. At one extreme are plants with more or less upright leaves, similar to those observed in New Zealand P. tenax, and at the other extreme there are plants with floppy leaves. The upright-leaved form is found more or less throughout the archipelago, whereas the floppy-leaved form is concentrated in the southern part of Chatham Island, Pitt Island, and on the other southern islands (e.g. South East and Mangere islands). Analysis of amplified fragment length polymorphism (AFLP) and simple-sequence-repeat (SSR) variation, and comparison with a diverse sampling of New Zealand Phormium suggested that both Chatham Islands forms are indigenous and part of a common gene pool. We found no evidence of hybridism with Phormium introduced from New Zealand. Floppy-leaved forms are therefore linked to typical upright leaved P. tenax through upright-leaved plants with bent tips, and do not require taxonomic recognition. AFLP and SSR data both support the view that a plant collected from Ranui Cove, Auckland Island, is descended from Chatham Islands material, and was most likely introduced there by Ngāti Mutunga and Moriori settlers during the 19th century.