Testing species limits of New ZealandPlantago(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 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.

A taxonomic revision of native New ZealandPlantago(Plantaginaceae)

“…There was support for four main clades of Australasian Plantago, two of which contained both New Zealand and Australian species, and several species relationships within each group were resolved. Additional recent studies using ITS sequencing (Tay et al 2010b), AFLPs (Meudt 2011) and molecular cytogenetics (Wong 2011) have begun to address outstanding taxonomic questions and the nature of polyploid species in New Zealand Plantago. Phylogenetic and network analyses of ITS sequence data (Tay et al 2010b) showed that lowland octoploid species P. picta and P. spathulata are genetically distinct.…”

“…Additional recent studies using ITS sequencing (Tay et al 2010b), AFLPs (Meudt 2011) and molecular cytogenetics (Wong 2011) have begun to address outstanding taxonomic questions and the nature of polyploid species in New Zealand Plantago. Phylogenetic and network analyses of ITS sequence data (Tay et al 2010b) showed that lowland octoploid species P. picta and P. spathulata are genetically distinct. However, ITS data could not distinguish the two alleged forms of another lowland octoploid species P. raoulii from each another, nor the octoploid species P. masoniae, P. triandra, and decaploid P. unibracteata from one another.…”

“…Tay et al (2010b) found molecular phylogenetic evidence for the allopolyploid origin of the 16-ploid P. udicola (as P. sp. ''Sylvester'') from octoploid parental species P. spathulata and P. raoulii.…”

New chromosome counts in New Zealand species ofPlantago(Plantaginaceae)

“…sequences (Tay et al 2010b) and AFLP markers (Heidi M Meudt in press), we refer to them here as 'P. aff.…”

“…Indeed, the identity and nature of all New Zealand Plantago, but especially P. sp. 'Sylvester' and the higher ploidy individuals of P. lanigera and P. unibracteata mentioned above, are being explored further with DNA sequencing (Tay et al 2010b), molecular cytogenetics (C Wong & BG Murray unpublished observations), morphometrics (HM Meudt in press), and AFLP DNA fingerprinting (HM Meudt unpublished observations. …”