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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 from internal 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. [ABSTRACT FROM AUTHOR]

Polyploidy is common in the widespread genus Plantago, and might be especially important in the evolutionary history of native New Zealand species of the genus. To further understanding of native New Zealand Plantago, mitotic and meiotic chromosome counts are reported from 58 individuals representing most native species and subspecies, and one introduced species, complementing previous studies by extending the number of individuals and the geographic range of taxa counted. Previous counts were confirmed for most Plantago lanigera (2n = 2x = 12), all P. raoulii, P. spathulata subsp. spathulata, P. spathulata subsp. picta, P. triandra subsp. triandra and P. triandra subsp. masoniae (2n=8x=48), most P. unibracteata (2n=10x=60), and all P. sp. 'Sylvester' (2n=16x=96). Novel counts include 2n=12x=72 for four individuals identified as P. unibracteata, and 2n=48 for four individuals from Sugarloaf Pass, South Island, referred to here as P. aff. spathulata. One of the eight naturalized species, P. major, was diploid with 2n=12. These results, together with other studies, suggest that all native New Zealand Plantago have a base chromosome number of x=6 and most polyploids are allopolyploids. [ABSTRACT FROM AUTHOR]