Testing species limits of New Zealand Plantago (Plantaginaceae) using internal transcribed spacer (ITS) DNA sequences

Abstract

Geological and climatic changes, coupled with long-distance dispersals, have resulted in relatively recent origins and radiations of many New Zealand plant lineages. Several have extensive morphological but low genetic variation, rendering taxonomic resolution difficult. This study presents population-level phylogenies and networks for the New Zealand species of Plantago (Plantaginaceae) using DNA sequences frominternal transcribed spacer (ITS) regions of the nuclear ribosomal genes. The data suggest that the two P. spathulata subspecies, and a 16-ploid entity (P. sp. 'Sylvester'), should be recognized at species rank. However, there was no evidence for divergence of: two P. raoulii forms; P. lanigera and P. novae-zelandiae; and two P. triandra subspecies. Several species and subspecies boundaries require revision with additional data (e.g. chromosome counts, morphological data, and additional DNA loci) needed. The high morphological variation but low sequence divergence found here could be caused by various factors, including incomplete speciation and/or hybridization. © 2010 The Royal Society of New Zealand.