Biodiversity of the vireya group of Rhododendron L. (Ericaceae) collections in New Zealand and their potential contribution to international conservation : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science at Massey University, Turitea, New Zealand
Rhododendron Subgenus Vireya sensu Argent (2006), commonly known as vireyas is an example of a group of plants with numerous taxonomic and conservation issues, making this group a challenge for development of conservation plans. In addition, recent molecular studies on the vireyas have revealed unexpected relationships that contrast with many of the previously known classification systems. Vireyas have been evaluated by the IUCN and have 63 taxa Red-Listed as threatened, and as New Zealand has 17 of these, they could have the potential to contribute to international conservation. Prior to developing a conservation plan, molecular techniques were used in an attempt to resolve some of the remaining taxonomic and conservation issues around the vireyas, utilizing a total of 352 accessions from approximately 160 taxa.
The initial phylogenetic analysis of 87 vireya accessions, using maximum parsimony analysis of the rpb2i intron 23 nucleotide sequences revealed that the sections Pseudovireya and Discovireya are monophyletic and sister to the rest of the vireyas. The remaining sections were paraphyletic or polyphyletic. Further phylogenetic analyses that included an additional 84 published sequences of the same nuclear region presented improved phylogenetic resolution, and the maximum parsimony analysis showed that the vireyas are monophyletic. This analysis also showed that the sections Pseudovireya and Discovireya are basal clades and not monophyletic, but sister to the rest of the vireyas. The phylogenetic analyses confirmed several known vireya relationships and resolved several taxonomic issues, and a new classification of vireyas is proposed. The genetic diversity analyses using microsatellite, RAPD and rpb2i sequence data were carried out on taxa with multiple accessions indicated that 14 out of 16 taxa showed significant genetic diversity indicating suitability for ex situ conservation.
This study confirmed that vireyas form a large and complex group with several remaining taxonomic issues, and it is clear that more taxa need to be studied to unravel its taxonomic complexity. This study has identified several vireya taxa in New Zealand collections that could be used as part of an ex situ conservation programme and a Conservation Plan for these is presented.