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Taxonomy, biogeography and evolution of plants
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RESEARCH ARTICLE
Contents Vol 20(1)

Molecular taxonomic clarification of Ptilotus exaltatus and Ptilotus nobilis (Amaranthaceae)

Kok K. Lee A , Dion K. Harrison A , Margaret E. Johnston A B and Richard R. Williams A
+ Author Affiliations
- Author Affiliations

A Centre for Native Floriculture, School of Land, Crop and Food Sciences, The University of Queensland, Gatton, Qld 4343, Australia.

B Corresponding author. Email: M.Johnston@uq.edu.au

Australian Systematic Botany 20(1) 72-81 https://doi.org/10.1071/SB06010
Submitted: 13 April 2006  Accepted: 28 November 2006   Published: 26 February 2007

Abstract

A complete botanical key for the genus Ptilotus R.Brown (family Amarathaceae) has not yet been published. Identifying the 100 or more Ptilotus species using morphological characters has been difficult because plants often exhibit slight morphological differences and intermediate characteristics common to several species, subspecies, varieties and forms. Ptilotus exaltatus Nees and P. nobilis (Lindl) F.Muell share many morphological characteristics, but are classified as different species predominantly based on inflorescence colour. The current study involved a molecular phylogenetic analysis of 14 Ptilotus species using sequence data from the internal transcribed spacer (ITS) regions ITS 1 and ITS 2 within the 18S–26S nuclear rDNA. Of the 39 accessions analysed, all except those identified as P. exaltatus and P. nobilis clustered according to their respective species based on their morphological taxonomy. In contrast, all 18 P. exaltatus and P. nobilis accessions formed a distinct monophyletic clade with 99% bootstrap values and a low level of sequence variation (GD = 0.002). Taking into account the lack of reliable morphological characters for separating P. exaltatus and P. nobilis, together with the ITS sequence data showing little genetic divergence or genetic structure, we propose that P. exaltatus and P. nobilis are conspecific.


Acknowledgements

This research was funded by the Centre for Native Floriculture, The University of Queensland and State Development, Trade and Innovation. We acknowledge the Mains Roads Department for giving the permits to collect plant material from the North Western District, South Western District and Central Western District. We also acknowledge Tony Bean, Laurie Jessop and Megan Thomas of the Queensland Herbarium, Jenny Milson and David Loch from the Department of Primary Industries and Fisheries (Longreach) and staff of University of Queensland Gatton nursery for their kind assistance and help.


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