A challenge to the taxonomy of Porphyra in Australia: the New Zealand red alga Porphyra rakiura (Bangiales, Rhodophyta) occurs in southern Australia, and is distinct from P. lucasii

Abstract

Extensive collections of Porphyra from throughout New Zealand since the early 1980s have revealed unexpectedly high diversity within the genus. From small-scale, opportunistic sampling of southern Australian Porphyra, small subunit ribosomal RNA gene (SSU) sequence data confirm the presence in Tasmania of a recently-described species of Porphyra, P. rakiura W.A.Nelson. This is the first report of P. rakiura from outside New Zealand. Analysis of rbcL–rbcS spacer DNA sequence from P. rakiura specimens and from an isotype specimen of P. lucasii Levring confirm that P. rakiura can be distinguished from the P. lucasii isotype at the molecular level as well as morphologically. A Western Australian specimen collected as P. lucasii provides a nuclear SSU sequence that is clearly different (92.1% similar) to that of P. rakiura, and rbcL–rbcS spacer sequence data identical to that of the P. lucasii isotype. Sequence data from the rbcL–rbcS spacer of a herbarium specimen from South Australia initially identified as P. lucasii, but with P. rakiura-like morphology, demonstrate that it is genetically distinct from P. rakiura and place it closer to, but not identical with, the P. lucasii isotype. This challenges the current taxonomic understanding of Porphyra in Australia, and of P. lucasii in particular.