AOBPreview originally published online on November 30, 2007
Annals of Botany 2008 101(6):881-899; doi:10.1093/aob/mcm294
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Biosystematics and Conservation: A Case Study with Two Enigmatic and Uncommon Species of Crassula from New Zealand
1 Terrestrial Conservation Unit, Department of Conservation, Private Bag 68908, Newton, Auckland, New Zealand
2 Allan Herbarium, Landcare Research, PO Box 69, Lincoln, New Zealand
3 School of Biological Sciences, The University of Auckland, Private Bag 92019, Auckland Mail Centre, Auckland 1142, New Zealand
* For correspondence. E-mail b.murray{at}auckland.ac.nz
Received: 25 April 2007 Returned for revision: 20 June 2007 Accepted: 2 October 2007 Published electronically: 30 November 2007
Background and Aims Crassula hunua: and C. ruamahanga have been taxonomically controversial. Here their distinctiveness is assessed so that their taxonomic and conservation status can be clarified.
Methods: Populations of these two species were analysed using morphological, chromosomal and DNA sequence data.
Key Results: It proved impossible to differentiate between these two species using 12 key morphological characters. Populations were found to be chromosomally variable with 11 different chromosome numbers ranging from 2n = 42 to 2n = 100. Meiotic behaviour and levels of pollen stainability were both variable. Phylogenetic analyses showed that differences exist in both nuclear and plastid DNA sequences between individual plants, sometimes from the same population.
Conclusions: The results suggest that these plants are a species complex that has evolved through interspecific hybridization and polyploidy. Their high levels of chromosomal and DNA sequence variation present a problem for their conservation.
Key words: Chromosome variation, Crassula, Crassula hunua, Crassula ruamahanga, Crassulaceae, conservation, phylogenetics, taxonomy, New Zealand flora
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